Web GIS Viewer

"Click link - See GIS data"
Good, fast, and free (for non-commercial use). Pick all three!
Gmap4 provides web GIS by combining Google maps
with a general purpose GIS viewer


No time to read this right now? OK. Just jump to the GIS example maps and take a quick look. You are almost certain to see something that you (1) find fascinating and (2) have never seen before on Google-map-based software. And if you find this GIS viewing feature to be particularly helpful, please keep in mind that Gmap4 is donate ware.
Another way to support Gmap4 is to purchase a property line map.

If you are new to Gmap4 please take a moment to look at the FAQ and the examples page. You will quickly see how Gmap4 links are made.

Last update: July 31, 2013

Table of Contents - View GIS data with Gmap4

Part 1 - Using Gmap4 to view maps that show GIS data
     Introduction - Gmap4 is a GIS viewer
     Things you can do with GIS data after the map opens
     Importance of metadata
     How does this work? A peek under the hood

Part 2 - Making Gmap4 links to display GIS data
     Gmap4 is a REST viewer
     REST metadata
     Gmap4 is a WMS viewer
     WMS metadata
     How to make a Gmap4 link that displays GIS data
     Using the ll and z parameter with GIS data
     Add a map title
     Add a map legend
     Limitations when displaying GIS data
     Web developers - Caution about using Gmap4 in iframes
     Miscellaneous tips and reminders

Part 3 - Sources for GIS data
     USA federal sources for GIS data
     USA state sources for GIS data
     USA other sources for GIS data
     Canada sources for GIS data
     Australia source for GIS data

Part 4 - Example Gmap4 links
     Example Gmap4 links showing GIS data - USA
     Example Gmap4 links showing GIS data - CANADA

Part 1 - Using Gmap4 to view maps that show GIS data

Introduction - Gmap4 is a GIS viewer

GIS stands for Geographical Information System. This technology works differently than downloading an entire file (GPX, KML, KMZ, etc). When you view GIS data the server hosting the data only sends you enough data to fill your screen. This data is delivered to your screen as a series of 'tiles'. Just like Gmap4 is a general purpose file viewing tool, it is now also a general purpose GIS viewer. This feature is known as "web GIS" since Gmap4 runs in your browser.

Why might you care? There is a vast amount of data on GIS servers that Gmap4 can display. Whatever your interest might be, there likely is data on a GIS server that you would enjoy seeing on a map. Some GIS data will be displayed as a new basemap with a solid background. Other GIS data will be displayed as transparent overlays that can be stacked on top of each other and then displayed on any basemap. Gmap4 lets you see both kinds of GIS data with familiar Google map controls.

You do not need to use complicated software that must be downloaded and installed in order to view GIS data. Instead, all you need to do is make a Gmap4 link that identifies the GIS data you want to view. And best of all, when you share your Gmap4 link with other people they do not need to know anything at all about GIS. All they need to know is "Click link - See GIS data".

You can open these links with most desktop browsers and with most browsers on most mobile devices including iPhones, iPads and Android devices. You can save any Gmap4 GIS link as a bookmark in your mobile browser and then quickly re-display that map anytime by opening that bookmark. When Gmap4 is opened on a smartphone or other mobile device it automatically displays an easy to use touch-friendly interface.

The data that you can now display by simply clicking a Gmap4 link is limited only by your ability to (1) locate that data on a GIS server and (2) make a proper Gmap4 link to display that data. These instructions and examples will get you going. Yes, there are a few new things you will need to learn. You can quickly get up to speed by reading these instructions and doing a bit of thoughtful experimentation. On your mark, get set, engage brain.

And if you make a really cool map that you want to brag about, please send me a link. I do not promise to publish them all, but I will certainly publish some. In particular I would enjoy seeing Gmap4 links that display topographic maps from countries other than the USA and Canada. (Those topographic maps are already hard coded into Gmap4.)

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Things you can do with GIS data after the map opens

GIS data can be added to the map as either (1) an additional basemap or (2) as a transparent overlay. After the map opens on your screen you can:
* Display any GIS basemap or any basemap hard-coded into Gmap4
* Switch any transparent overlay on/off
* Switch all transparent overlays on/off together
* Change the stacking order for the transparent overlays

In addition, all of the Gmap4 features work just fine with GIS data. If you do Menu ==> "Link to this map" then you can copy a link that will reproduce the map you see on your screen complete with the GIS data. You can use the Menu ==> "My Location" feature and see your location on the map. You can display a UTM grid on top of the GIS data. You can display GPX, TPO, KML, KMZ, etc files on top of GIS data.

The following link opens a map that has one additional basemap and three overlays. Each overlay is produced by one "&wms=" or "&rest=" parameter in the Gmap4 link. Open this map and then open the 'map type' menu (button that says "All white basemap"). Basemaps that are hard-coded into Gmap4 appear in bold type while basemaps that are added as a result of parameters in the Gmap4 link appear in normal type. If any overlays are available for the map then they are listed in the "Overlay" section of the 'map type' menu.

Map with three transparent overlays
http://www.mappingsupport.com/p/gmap4.php?ll=38.548166,-99.162598&z=5&t=Weather_radar,Transportation,States&wms=http://nowcoast.noaa.gov/wms/com.esri.wms.Esrimap/obs?name=Weather_radar&layers=RAS_RIDGE_NEXRAD&transparent=true&version=1.1.1&rest=http://services.nationalmap.gov/ArcGIS/rest/services/transportation/MapServer?name=Transportation&transparent=true&wms=http://webservices.nationalatlas.gov/wms?name=States&layers=states&transparent=true

Gmap4 always displays exactly one basemap. The name of the current basemap is always displayed on the 'map type' button. If a Gmap4 link includes a transparent overlay(s), then the "All white basemap" is automatically added to the list of map types. Sometimes a very nice way to present transparent GIS overlays is to display them on the "All white basemap".

An important concept for transparent overlays is their stacking order. Each overlay that is 'on' has a number assigned. Overlay #1 is at the bottom of the stack. The highest numbered overlay is at the top of the stack. Data on an overlay that is higher in the stack will cover up any data at the same location on overlays that are lower in the stack and also cover up any data in that same location on the basemap.

There are three things you can do with transparent overlays while viewing the map.

First, you can turn individual overlays on and off. Simply click the overlay on the 'map type' menu. An overlay that is 'off' does not have a number assigned to it since it is not visible.

Second, you can turn all overlays on and off together. The 'map type' menu includes two choices for this purpose. If you turn all overlays off and then turn them all back on then (1) all transparent overlays will be turned 'on' including any that were 'off' when the map opened and (2) the stacking order will be the order in which the &wms= and &rest= parameters appear in the Gmap4 link.

Third, you can change the stacking order. If you turn one overlay off then it is removed from the stack. If you then turn that same overlay back on it will be added to the top of the stack and data on this overlay will cover up any data at that same location that is present on the other overlays or on the basemap. Another way to change the stacking order is to turn all the overlays off and then turn them back on one at a time. The first overlay that you turn back on will be at the bottom of the stack and the last overlay you turn back on will be at the top of the stack.

Tip for smartphone and tablet users. To save any Gmap4 link as a bookmark in the browser on your smartphone or tablet, email that link to yourself. Then open that link with your mobile browser and save it as a bookmark. I know this works on an iPhone 4s using iOS 6.1.3 and Safari.

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Importance of metadata

The word "metadata" means information about data. A good example of metadata is the names of the layers of data on a GIS server. In order to make a Gmap4 link that will display GIS data when the link is clicked you usually will need to know the names of the layers of data that your map will display. In other words, you will need to know some metadata. In Part 2 of these instructions you will learn how to display the metadata from a GIS server.

How does this work? A peek under the hood

Think of a data file that shows the approximate boundary line of many different kinds of publically owned land across the USA. Such a data file would be huge. Now assume you only want to see a map for a small part of the USA. It would take a long time and waste resources to download that huge file to your computer when you only want to see a small part of that data.

GIS fills this need. Here is how it works.

Map software like Gmap4 always knows the latitude longitude values that define the portion of the world displayed on your screen. When you want to view data from a GIS server Gmap4 sends those latitude longitude values to that GIS server. In return, the GIS server sends back enough data to fill your screen. This data is delivered to you in a series of small files called "tiles". Each tile is 256 pixels wide by 256 pixels high. Sometimes if a GIS server is a bit slow you can see these tiles appear one at a time on your screen.

Be patient. If the server is extremely busy then it might take a few seconds for the server to send all the tiles to you that are needed to fill your screen. Occasionally you might not get any GIS data at all. Perhaps that server is off-line.

Tip: If some of the GIS tiles display on your screen but there are some that are obviously missing, try zooming in or out, wait for the tiles to display and then go back to the zoom level you want.

No GIS data on the screen? Try zooming in. Some GIS servers only display data at certain zoom levels.

Part 2 - Making Gmap4 links to display GIS data

The data that you can now display by simply clicking a Gmap4 link is limited only by your ability to (1) locate that data on a GIS server and (2) make a proper Gmap4 link to display that data. These instructions and examples will get you going. Yes, there are a few new things you will need to learn. You can quickly get up to speed by reading these instructions and doing a bit of thoughtful experimentation. On your mark, get set, engage brain.

And if you make a really cool map that you want to brag about, please send me a link. I do not promise to publish them all, but I will certainly publish some. In particular I would enjoy seeing links that display topographic maps from countries other than the USA and Canada. (Those topographic maps are already hard coded into Gmap4.)

Do you have a smartphone? Gmap4 works just fine in most browsers on most smartphones, tablets and other mobile devices. When you open Gmap4 with a browser on a mobile device you will automatically see an easy-to-use touch-friendly interface. You have to be online to use Gmap4. There is no offline capability.

Gmap4 can display GIS data that is available via either the REST interface or WMS interface. The REST interface was developed by ESRI which is the leading vendor of GIS software. The WMS interface is open source. In the following sections you will learn how to make a Gmap4 link to display GIS data from both REST servers and WMS servers. In fact, GIS data form both types of servers can be combined in a single Gmap4 link.

Tip: If the same data is available via both WMS and REST then use the REST server since your map might load faster. Also the REST metadata often has a better description of the data layers than the WMS metadata.

Gmap4 is a REST viewer

In general, there are several different ways that GIS data might be accessed. Many (but not all) servers that are hosting GIS data are setup to allow access via the REST interface and/or WMS (Web Mapping Service) interface. Some servers allow both interfaces and some only allow one or the other. For servers that offer both methods, you should choose REST since it might offer better performance than WMS. This section shows you how to make a Gmap4 link to display GIS data using the REST interface.

To make a Gmap4 link that will display GIS data using the REST interface, include one or more "&rest=" parameters in your Gmap4 link.

To add a basemap to the ones already hard-coded in Gmap4, write the "&rest=" parameter like this:

     &rest=__________?name=__________
or
     &rest=__________?name=__________&layers=__________

In the two links above, replace the underlines as follows:
Underline 1: Full http link pointing to the GIS server. Be sure to put a "?" after this link.
Underline 2: Short name you make up. Use an underline character instead of a space!
Underline 3: One or more names used on the server to identify layers of data. Separate the names with commas and no spaces like so: &layers=name1,name2,name3.....

To find http links for some GIS servers, see the section on this page titled
Sources for GIS data. Of course you could also do a Google search.

The short name you make up is used by Gmap4 in the 'map type' menu and it is not used by the GIS server. If you forget to make up your own short name then a default name is assigned. That default short name is "GIS_" followed by a number.

To see how to find out the names of the data layers on a GIS server, see the section on this page titled REST metadata.

The metadata will also tell you if this REST data is already made into tiles that are stored in a cache on the server ("tiled") or if the map tiles are generated on-the-fly and sent to your map ("dynamic"). Tiled data displays faster but will likely limit how far you can zoom in before the data becomes fuzzy. If you are displaying "tiled" data then you do not need to include the "&layers=" parameter in the Gmap4 link but you should still make up a short name for that data.

If the names of the data layers on the GIS server are numbers, then you can specify number ranges to identify the data you want to have displayed on your map.

     &layers=1-5,8,10,14-16

If you do not include the "layers=" parameter then the server will send you the default layer(s) - if any. But if none of the layers of data on the server have been designated as the default, then the server will not send you anything except maybe blank tiles. If you include the "layers=" parameter in your Gmap4 link then you can supply a comma-separated list (no spaces) of layer names.

This concept of a server possibly having one or more layers designated as the default only applies when you use the "&rest=" parameter. If you use the "&wms=" parameter in your Gmap4 link then you must specify the layers you wish to see on your map.

To add a transparent overlay that can be displayed on top of any basemap and stacked with other REST and/or WMS overlays, write the "&rest=" parameter like this:

     &rest=__________?name=__________&transparent=true
or
     &rest=__________?name=__________&layers=__________&transparent=true

A Gmap4 link can include more than one "&rest=" and/or "&wms=" parameters. Also, be sure to put any "&wms=" and "&rest=" parameters at the end of the Gmap4 link. These two kinds of parameters can be in any order. They just need to be at the end of the Gmap4 link.

For example, when the following map opens the basemap is the Google street map and much of California will be displayed. On top of that basemap will be a transparent overlay showing the county boundaries and county names.

County boundary map
http://www.mappingsupport.com/p/gmap4.php?ll=37.877021,-121.14624&z=9&t=m,Counties&rest=http://services.nationalmap.gov/ArcGIS/rest/services/govunits/MapServer?name=Counties&layers=3,13&transparent=true

If occasionally the GIS data seems to be incomplete, try zooming in or out. Wait for the GIS data to appear on your screen and then change the zoom level to the one you really want.

In addition, the REST interface allows the following advanced ways to use the "&layers=" parameter:

     &layers=show:name1,name2,name3...
          Only the layers specified in this list will be exported. Same as &layers=name1,name2,name3...

     &layers=hide:name1,name2,name3...
          All layers except those specified in this list will be exported.

     &layers=include:name1,name2,name3...
          In addition to the layers exported by default, the layers specified in this list will be exported.

     &layers=exclude:name1,name2,name3...
          The layers exported by default excluding those specified in this list will be exported.

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REST metadata

This section uses REST metadata from the U.S. Forest Service as an example.

When you are looking for REST metadata on a website look for links labelled "REST service", "REST endpoint" or something similar. Sometimes a link labelled "Web Mapping Service" (WMS) will also lead to REST metadata.

Please open the following Forest Service link:
http://apps.fs.fed.us/ArcX/rest/services/EDW

The EDW screen lists several dozen kinds of data. As long as the end of a line says "MapServer", Gmap4 can display that data. Sometimes you will see "Feature Service" or WFS on similar lists. When using REST, Gmap4 can only display "MapServer" data and it cannot display Feature Service data or any other type of data. So you want to make sure that information you are trying to view with Gmap4 is identified as "MapServer" in the metadata.

Now look toward the bottom of the EDW list and click the link for "EDW/EDW_Wilderness_01 (MapServer)".

1. After the screen refreshes go to the bottom of this screen. Make sure that:
      A. The heading "Supported Operations" includes "Export Map"
      B. The heading "Supported Interfaces" includes "REST"

2. Near the top of the screen, find the heading "Layers". Under this heading is a list of one or more layers of data that Gmap4 can display. Each layer has a number and a descriptive name. Use the number in the Gmap4 link and not the descriptive name. For example, to display layer 0 your Gmap4 link would include &layers=0.

3. Near the top of the screen, find the heading "Single Fused Map Cache". Usually this value will be "false". This means that when you ask the GIS server to send you enough tiles to fill your screen, the server produces those tiles on-the-fly in response to your request. These are called "dynamic" tiles. This type of layer may or may not be designed so you can display it as a transparent overlay. The easiest way for you to find out if a layer can be displayed as a transparent overlay (instead of a non-transparent basemap) is to make a Gmap4 link yourself and test the layer.
   Sometimes this value will be "true". This means that the GIS server has pre-made tiles all ready to go. These are called "cached" tiles and they usually display faster than dynamic tiles. Often times cached tiles include data from several different dynamic layers. Since all of this data is combined in the process of making the tiles and storing them in the cache, you will not be able to turn individual layers on/off. In other words, when you are displaying cached tiles, all the individual layers have been combined into a single layer.

4. Find the heading "Supported Interfaces" again near the bottom of the screen. If it also says WMS then this same data is available via both the REST interface and the WMS interface. I recommend you always use the REST interface when given the choice since performance may be better than the WMS interface. However, the WMS metadata is useful since it will likely have a link to an image file that holds a legend for this data. The documentation for this GIS viewing feature shows you how to (1) find this legend link in the WMS metadata and (2) make a map title that includes this legend link.

Tip: You may have to zoom in to see the GIS data. When you see some GIS data you may need to zoom in more to see all the GIS data.

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Gmap4 is a WMS viewer

Some GIS servers allow the WMS interface but do not allow their data to be accessed via the REST interface. To make a Gmap4 link that will display GIS data using the WMS interface, include one or more "&wms=" parameters in your Gmap4 link.

To add a basemap to the ones already hard-coded in Gmap4, write the "&wms=" parameter like this:

     &wms=__________?name=__________&layers=__________

To add a transparent overlay that can be displayed on top of any basemap and stacked with other overlays, write the "&wms=" parameter like this:

     &wms=__________?name=__________&layers=__________&transparent=true

In the two links above, replace the underlines as follows:
Underline 1: Full http link pointing to the GIS server. Be sure to put a "?" after this link.
Underline 2: Short name you make up. Use an underline character instead of a space!
Underline 3: One or more names used on the server to identify layers of data. You must specify at least one layer name. Separate multiple names with commas and no spaces like so: &layers=name1,name2,name3....

The short name you make up is used by Gmap4 in the 'map type' menu and it is not used by the GIS server. If you forget to make up your own short name then a default name is assigned. That default short name is "GIS_" followed by a number.

To see how to find out the names of the data layers on a GIS server, see the section on this page titled
WMS metadata.

If the names of the data layers on the GIS server are numbers, then you can specify number ranges to identify the data you want to have displayed on your map.

     &layers=1-5,8,10,14-16

The above instructions apply to GIS servers that are using WMS version 1.3.0. To display data from a server that is using WMS version 1.1.1, write the "&wms=" parameter like this:

     &wms=__________?name=__________&layers=__________&version=1.1.1
or
     &wms=__________?name=__________&layers=__________&transparent=true&version=1.1.1

Note: Most GIS servers that allow access via WMS use either WMS 1.1.1 or the newer WMS 1.3.0 specification. Gmap4 supports both of these WMS versions and treats 1.3.0 as the default. There are also two older versions of the WMS specification that are not used very much. They are known as 1.0.0 and 1.1.0. Gmap4 does not support these two older versions.

For example, the following Gmap4 link has two "&wms=" parameters. Both sets of wms data are transparent overlays that display on top of any basemap. The first WMS parameter uses version 1.1.1 and displays weather radar data. The second WMS parameter uses the default version WMS of 1.3.0 and displays an outline of the states on top of the radar images. And where you think you see a space in the link there is really an underline character.

Weather radar map
http://www.mappingsupport.com/p/gmap4.php?ll=37.544578,-99.140625&z=5&t=t1,Weather_radar,states&wms=http://nowcoast.noaa.gov/wms/com.esri.wms.Esrimap/obs?name=Weather_radar&layers=RAS_RIDGE_NEXRAD&transparent=true&version=1.1.1&wms=http://webservices.nationalatlas.gov/wms?name=states&layers=states&transparent=true

If occasionally the GIS data seems to be incomplete, try zooming in or out. Wait for the GIS data to appear on your screen and then change the zoom level to the one you really want.

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WMS metadata

Tip: If the same data is available via both WMS and REST then use the REST server since your map might load faster. Also the REST metadata often has a better description of the data layers than the WMS metadata.

In order to build your own Gmap4 links that display GIS data from a WMS server you need to know two things:
1. HTTP address of the WMS server
2. Name of one or more layers of data on that server

In order to learn the names of the data layers that are available on the WMS server, you need to ask the server to show you its metadata. Usually you can get the metadata information by entering a link like one of the following into your browser. Replace the underline with the full http:// link for the WMS server.

________________?request=GetCapabilities (most servers using WMS 1.3.0 accept this form)
or
________________?request=GetCapabilities&service=WMS&version=1.3.0
or
________________?request=GetCapabilities&service=WMS&version=1.1.1

Generally you should try the metadata links in the order shown above. The first 'GetCapabilities' format listed above works most of the time because most WMS servers use WMS version 1.3.0 and that is the default version used by Gmap4. If you want to display data from a server using WMS version 1.1.1 then you must specify that version both when you get the metadata and in your Gmap4 link.

For example, please go to this page for the National Atlas (which is only available via WMS)
http://nationalatlas.gov/infodocs/wms_techinfo.html. This page has a dozen or so links to metadata. Since the National Atlas has over 2,400 layers of data the metadata has been divided up by category.

Click the link for the 'Boundaries' category. Don't panic. You only need to know a little bit about the information you see on your screen.

First, double-check the link that points to the WMS server. It is good to get in the habit of doing this step since sometimes the link for the metadata and link for the WMS server are a bit different. Look down a few lines for a line that starts "<OnlineResource". That line has the link address for the WMS server. Note that in this case the wms server link is slightly different than the link that displays the boundaries metadata.

wms server link = http://webservices.nationalatlas.gov/wms?
metadata link = http://webservices.nationalatlas.gov/wms/boundaries?

Second, find the name of the first layer that this WMS server can display. Each of these layer names is on a line that looks like this:
<Name>layer_name_is_here</Name>

The easiest way is to search the file (control F on a PC) for the 6 characters <Name>. But there is a trick to this. When you find <Name> you need to look at the line just above. If that line (1) starts out <Layer and (2) also includes any other word, then inside of the name tags is the name of a data layer that can be displayed. Got it? Now we will give it a try.

Please search the boundaries metadata for the first layer that can be displayed.

Did you find the line that says <Name>layer_name_is_here</Name>? This layer displays the congressional districts.

Note that the line just above includes "opaque=0". That indicates it should be possible to display this layer with a transparent background. If you saw "opaque=1" instead, then the background of the data layer is most likely one or more solid colors.

You are now ready to use the metadata to complete the WMS parameter by filling these blanks:
&wms=__________?name=__________&layers=__________&transparent=__________

It should look like the following when you are done although the name you picked for this data might be different than the name picked:
&wms=http://webservices.nationalatlas.gov/wms?name=Congressional_districts&layers=cdl&transparent=true

And here is a complete Gmap4 link that will display the Google street map and a transparent overlay showing the congressional district boundaries when the link is clicked:
http://www.mappingsupport.com/p/gmap4.php?ll=37.896038,-98.96875&z=5&t=m,Congressional_districts&wms=http://webservices.nationalatlas.gov/wms?name=Congressional_districts&layers=cdl&transparent=true

Tip for viewing metadata for WMS version 1.1.1
If you enter a link into your browser asking to see some metadata from a server using the older WMS version 1.1.1, then you will likely be asked if you want to download that file. If you use a PC and Firefox, here is a better approach. I use the freeware Notepad++ for lots of file editing tasks.
1. If you do not already have an editor that you use for XML files, download and install Notepad++.
2. Try to open thislink with Firefox: http://giswebservices.massgis.state.ma.us/geoserver/wms?request=GetCapabilities&service=WMS&version=1.1.1. This link displays metadata for a WMS version 1.1.1 server run by the State of Massachusetts.
3. When you are asked to save or open the metadata file, use the Firefox menu bar and go to Tools > Options > Applications. Change "application/vnd.ogc.wms_xml" to always open with Notepad++. If you see "application/vnd.ogc.se_xml" then change that one also.

Now when you surf Firefox to a version 1.1.1 GetCapabilities file, it will automatically open in Notepad++.

Remember, when you are displaying a layer from a version 1.1.1 WMS server then you must include &version=1.1.1 as part of the wms parameter in the Gmap4 link.

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How to make a Gmap4 link that displays GIS data

Here is an easy way to get Gmap4 to make a link for you that will display a map that is (1) centered anywhere you want on the planet (except really close to the north pole or south pole), (2) be zoomed to the level you want and (3) show the GIS data you want to see when the link is clicked.

Step 1. Find the GIS data you want to see and build a very basic Gmap4 link.

This demo will use some weather data from NOAA that is close to real time. Here are the WMS parameters for this demo:

Air temperature:
&wms=http://nowcoast.noaa.gov/wms/com.esri.wms.Esrimap/obs?name=Air_temperature&layers=OBS_MET_TEMP&transparent=true&version=1.1.1

Wind speed arrows:
&wms=http://nowcoast.noaa.gov/wms/com.esri.wms.Esrimap/analyses?name=Wind_speed&layers=RTMA_PT_WINDVECT_01,RTMA_PT_WINDVECT_05,RTMA_PT_WINDVECT_10,RTMA_PT_WINDVECT_15&transparent=true&version=1.1.1

Here is a very basic Gmap4 link. Notice that this link does not have a ll (map center) or z (zoom level) parameter. It also does not have a t parameter (used to turn on the GIS data).
http://www.mappingsupport.com/p/gmap4.php?wms=http://nowcoast.noaa.gov/wms/com.esri.wms.Esrimap/obs?name=Air_temperature&layers=OBS_MET_TEMP&transparent=true&version=1.1.1&wms=http://nowcoast.noaa.gov/wms/com.esri.wms.Esrimap/analyses?name=Wind_speed&layers=RTMA_PT_WINDVECT_01,RTMA_PT_WINDVECT_05,RTMA_PT_WINDVECT_10,RTMA_PT_WINDVECT_15&transparent=true&version=1.1.1

Step 2. Make the map look the way you want it to look on your screen.

A fast way to pan and zoom the map to a place you want to see is to use Menu ==> Search. After the search is done, remember to close the search bar.

To turn on the two transparent overlays, open the 'map type' menu (button in upper right - lower right on mobile), go to the bottom of the map type list and click on both of the overlays. Keep in mind that the transparent overlays stack on top of each other. Data on a higher numbered overlay will cover up data on a lower numbered overlay. To change the stacking order, turn all the overlays off and then turn them on in a different order.

Select the basemap you want to have displayed when the map opens. Keep in mind that GIS data is seen by Gmap4 as a series of jpg or png image 'tiles' and Gmap4 does not have any way to alter anything on those images. Different GIS data will look better on different basemaps. Experiment. Some GIS data will look great (or at least be easier to read) on the "All white basemap" together with another layer that is an outline of the states.

Fine tune the center of the map by dragging the map and adjust the zoom if needed.

Step 3. Ask Gmap4 to make the map link for you

Click Menu ==> Link to this map. The link you see will reproduce the map you have on your screen.

Look closely at the link and you will see that the following additional parameters have been added just after the first "?" in the link:
"ll=" Latitude and longitude (WGS84 datum) for the center of the map.
"z=" Zoom level. A rightclick on a desktop also displays the zoom level.
"t=" Comma-separated list (no spaces) of one basemap and any transparent overlays that display when the map opens.

A Gmap4 map always displays one and only one basemap. When the "&t=" parameter points to a list of map types, there should not be more than one basemap in the list and any additional basemaps in this list are ignored. If the "&t=" parameter does not include any of the basemaps then:
     A. If there is no "&t=" parameter in the Gmap4 link, then the t1 (Google terrain) basemap will be displayed.
     B. If the "&t=" parameter only lists the names of one or more transparent overlays, then the "All white basemap" will be displayed.

The map types in the "&t=" list that are transparent overlays are stacked in this order when the map is opened: 1,2,3,etc. Thus, the last overlay in the "&t=" list is at the top of the stack (i.e. has the highest number) and data on this 'highest' overlay will cover up data on all the other overlays.

The order of the &rest= and &wms= parameters in the Gmap4 link should likely match the stacking order shown by the overlay names in the &t= parameter of the Gmap4 link. Here is the reason. At the bottom of the 'map type' menu are two choices that say "Remove all overlays" and "Display all overlays". Choosing "Remove all" turns off all of the transparent overlays. Choosing "Display all" turns all of the overlays on even if some of them were not turned on by the &t= parameter when the map first opened. The stacking order that results from "Display all" is the order of the &rest= and &wms= parameters in the Gmap4 link.

Notice that the short name you make up for each &rest= and &wms= parameter in your Gmap4 link is used in the 'map type' menu and maybe in the "&t=" parameter list. If you forget to make up you own short name then a default name is assigned. That default short name is "GIS_" followed by a number.

There are two situations where you usually should delete the "ll=" and "z=" parameter from the link produced by Gmap4. First, the "q=" parameter is used to display a GPX, KML, KMZ and certain other file types. If the Gmap4 link *does not* include a ll or z parameter then the program will automatically center and zoom the map such that all of the data in the file is on the user's screen irrespective of screen size. Second, if the Gmap4 link contains a "&markers=" parameter then you need to look a bit closer. Sometimes the "&markers=" parameter will contain coordinate data. When that is the case, you likely should not have any ll or z parameter in the Gmap4 link and instead let the program automatically center and zoom the map such that all the data in the "&markers=" parameter is on the map.

You should assume that people with many different sizes of screens - from smartphones to desktops - will be viewing your map. If your map displays (1) data from a file or (2) coordinate data via the "&markers=" parameter, then usually your Gmap4 link should not include the "ll=" and "z=" parameters. If those two parameters are not in the link, then Gmap4 will automatically center and zoom the map such that all of the data from the file or "&markers=" parameter is on the user's screen irrespective of the size or resolution of that screen.

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Add a map title

You can add a title to a map by using the "&markers=" parameter. The title will be displayed in the upper left corner of the map. Here are some examples:

&markers=title=MyTitleHere

&markers=title=<b>My%20Title%20Here</b>

&markers=title=<b>Line1<br%20/>Line2</b>

&markers=title<div%20style="font-weight:bold;">=<b>Line1<br%20/>Line2</b></div>

The characters %20 are computer-speak for a space. Often times a space in a link will cause problems so use %20 instead of a space.

The last three examples will cause the title to appear in bold type. The 3rd and 4th examples have a title that appears on two lines. The last example uses inline CSS to style the title.

The location of the markers parameter in the Gmap4 link is important. Place the markers parameter right before the first wms or rest parameter.

For an example of a map link with a title, see the "Earthquake Risk" map in the section titled
"Example Gmap4 links showing GIS data" further below.

The markers parameter can do a lot more besides add a title to the map. For more information about this feature please go to the Gmap4 help page and download the pdf file 'Delimited Data' and search that file on 'markers'.


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Using the ll and z parameter with GIS data

Gmap4 can display:
1. Data stored in a file that is online, or
2. Data stored in the Gmap4 link (map-in-a-link), or
3. Data stored on a GIS server, or
4. Data stored on a GIS server together with either #1 or #2.

When Gmap4 displays data stored in a file or map-in-a-link, then you do not need to specify the ll and z parameters in the Gmap4 link. If such a Gmap4 link does not include a ll or z parameter, then the map will open and automatically be centered and zoomed such that all of the data from the file or map-in-a-link is on the user's screen. It works this way on any size screen from smartphones to desktops. For example, the following link displays a KML file. Note that the link does not have either a ll or z parameter.

http://www.mappingsupport.com/p/gmap4.php?q=http://www.mappingsupport.com/p/gmap4/helpfile/Stafford_Creek.kml&t=t4

By contrast, Gmap4 does not know anything about the content of GIS data. If you make a Gmap4 link that only displays GIS data and the link does not include a ll and z parameter then be default when your map opens on the screen it will be zoomed way out. On a desktop, the default is to show a map of the world.

Therefore, if you make a Gmap4 link to display GIS data and not data from any file, then if you want the map to open and already be zoomed in somewhere you need to include a ll and z parameter in the Gmap4 link. The ll parameter specifies the latitude,longitude for the map center and the z parameter specifies the zoom level.

In picking a ll and z parameter to use, keep in mind that there are all kinds of screen sizes from smartphones to extra large desktops. On a 1280x1024 screen the following link shows (1) all of the 'lower 48' states from the west coast over to the middle of New Hampshire and (2) most of Cuba. If you open the same link with most smartphones, you will only see the central part of the USA.

http://www.mappingsupport.com/p/gmap4.php?ll=35.960476,-96.81491&t=m&z=5

Usually if you make a Gmap4 link that (1) shows GIS data and (2) does not show data from a file, then you should include a z and ll parameter in the Gmap4 link in order to zoom and center that map such that the GIS data is displayed on the screen when the map opens. Remember that the Menu ==> 'Link to this map' feature of Gmap4 will display a link that includes a z and ll parameter. That link will reproduce the map you see on your screen.

Add a map legend

If you are making a Gmap4 link that uses the WMS interface to display GIS data then there likely is a graphic file already made that contains a legend for that data. The metadata for that WMS service includes a link for that graphic file. If you include that link in a title on your map, then people viewing your map will have an easy way to see the legend simply by clicking that link.

To find the link to the legend image open the WMS metadata and find the entry for the GIS data your map is displaying. Then look down until you see "LegendURL" and there is the link to the legend image.

Copy that link and paste it into a browser to see the legend image and decide if it is something you would like to use. Bad news. Some of these legend images are so small that they are illegible. If you find a poor quality legend then email the people responsible for the WMS data and ask them to produce a legend that is legible when the legend link is used in a browser.

Use the "&markers=" parameter to add a title to your map that contains a link to the legend image. Below is a suggested standard way to make a map title that includes a legend. Replace the first underline with the title of your map. Replace the second underline with the link to the image with the legend. %20 is computer-speak for a space and is used since spaces in links often cause problems. If your map title includes any spaces then use %20 instead of a space.

&markers=title=<b>__________<br%20/><a href='__________'%20target='_blank'>Legend</a></b>

And here is an example showing how the above format is used to place a title and legend link on the "Earthquake Risk" map in the section of example maps further down on this page.

&markers=title=<b>Earthquake%20Risk<br%20/><a href="http://webservices.nationalatlas.gov/wms?version=1.3.0&service=WMS&request=GetLegendGraphic&sld_version=1.1.0&layer=seihaz&format=image/png&STYLE=default'%20target='_blank'>Legend</a></b>

Data that Gmap4 can display via the REST interface also often has a map legend. Look at the REST metadata that lists the various layers. Just above that list of layers, look for a link labelled "Legend".

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Limitations when displaying GIS data

Gmap4 does not have any way to know anything about the nature of the data on the tiles that a GIS server puts on your screen. In other words, Gmap4 cannot change the line width or line color of GIS data. Likewise, there is no way to let you click on this type of GIS data and then see a popup with more information.

If the GIS tiles are grossly misaligned then try using the basemap "m" (Google street map) in your Gmap4 link. This problem appears to be a Google bug.

Web developers - Caution about using Gmap4 in iframes

This section is for people that design web pages. If that is not you then you can skip this section.

The issue of embedding Gmap4 in an iframe is important because (1) each time Gmap4 starts the Google map Application Program Interface (API) is loaded and (2) after Gmap4 loads that API 25,000 times on average in one day then I have to pay Google for additional API loads in that same day otherwise Gmap4 stops working until the next day.

You can read more about this pricing policy at:
https://developers.google.com/maps/documentation/javascript/usage

Each time someone looks at a web page that includes Gmap4 embedded in an iframe, the Google map API is loaded. If the person viewing that web page is doing so because of some other content on that page and does not care about the embedded map, then that API load is 'wasted'.

Bottomline: You are welcome to embed one Gmap4 map per webpage as long as you design that page with care so a person looking at that page most likely wants to see the map. For example, it is fine to embed a Gmap4 map in an iframe on a web page that describes a specific trail.

If you do use an embedded Gmap4 map then it is a 'best practice' to include a link to a full screen map under the embedded map.

Remember, Gmap4 is free for non-commercial use. For information about commercial use of Gmap4 please see:
http://www.mappingsupport.com/p/gmap4_commercial.html

I consider trail guide sites and forums that generate revenue by displaying ads to be non-commercial if anyone can signup for free and the content on the site is free.

Questions? Send me an email.

Miscellaneous tips and reminders

GIS data covers up data on the basemap.

Transparent GIS overlays that are higher in the stack cover up transparent GIS overlays that are lower in the stack.

Sometimes the only way to tell for certain if a GIS layer has a background that can be transparent is to make a Gmap4 link and test it.

Put all "&rest=" and "&wms=" parameters at the end of the Gmap4 link.

The default basemap is either "t1" (Google terrain) or "All white basemap" depending on how the Gmap4 link is written.

Part 3 - Sources for GIS data

Below are various sources for GIS data that are available via REST and/or WMS. If you see any bad links or have a suggestion for additional sources to add to this list, please send me an email.

USA federal sources for GIS data

The two sections above titled REST metadata and WMS metadata explain how to use these links. If you have not yet read those sections, then now would be a good time to do so.

This is only a partial list of federal sources that have GIS data that you can view simply by making a Gmap4 link.

National Atlas (WMS only)
USA federal government
Metadata: http://nationalatlas.gov/infodocs/wms_techinfo.html

The National Map (REST and WMS)
U.S. Geological Survey
Metadata: http://viewer.nationalmap.gov/example/services.html
Homepage: http://nationalmap.gov/

Natural Hazards Support System (REST and WMS)
U.S. Geological Survey
Homepage: http://nhss.cr.usgs.gov/data.shtml
Scroll down on the homepage for metadata links.

National Weather Service (REST and WMS)
National Oceanic and Atmospheric Administration (NOAA)
Complete list: http://gis.srh.noaa.gov/ArcGIS/rest/services

This page leads to a subset of the complete list but likely will be helpful the first time you look at this information.
http://www.nws.noaa.gov/gis/otherpage.html

National Park Service (REST)
Natural Resource Stewardship and Science Map services
Metadata: http://irmaservices.nps.gov/arcgis/rest/services

U.S. Forest Service (REST and WMS)
Metadata: http://apps.fs.fed.us/ArcX/rest/services/EDW/

Bureau of Land Management (REST and WMS)
Metadata: http://www.geocommunicator.gov/ArcGIS/rest/services

U.S. Fish and Wildlife Service (REST and WMS)
National Wetlands Inventory
Metadata: http://107.20.228.18/ArcGIS/rest/services/Wetlands/MapServer

Environmental Protection Agency (REST and WMS)
metadata: http://water.epa.gov/scitech/datait/tools/waters/services/mapping_services.cfm

Office of Coast Survey (WMS)
National Oceanic and Atmospheric Administration (NOAA)
Coastal charts and much more
http://www.nauticalcharts.noaa.gov/csdl/web_mapping.html
Example metadata for the "Approach" coastal charts: http://encdirect.noaa.gov/arcgis/services/encdirect/enc_approach/MapServer/WmsServer?request=getcapabilities&service=wms

US Army Corps of Engineers (WMS)
Overview of some of their data
http://geo.usace.army.mil/pgis/f?p=632:1:1598396437633401:::::
Metadata: https://rsgisias.crrel.usace.army.mil/cgi-bin/wms/publicfuds_wms?service=wms&version=1.1.1&request=GetCapabilities

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USA state sources for GIS data

The sections REST metadata and WMS metadata explain how to use these links. If you have not yet read those sections, then now would be a good time to do so.

Thanks to the GIS program at the University of Wisconsin - Eau Claire (http://www.uwec.edu/geography/index.htm) for tracking down many of these links. All links are working as of July 3, 2013. Please let me know about any links that die.
If you are on a state website and find a source for GIS data that is not listed below and that data is available via either REST or WMS, please send me an email and I will add that data source to this list.

Alabama
No state government web site found yet that offers GIS data via the REST interface or WMS interface. Do you know of any?

Alaska
Homepage: http://www.alaskamapped.org/data/wms-wfs-wcs-web-service-feeds
Several WMS URLs are listed a short way down on this page.

FAA charts: http://wms.alaskamapped.org/faa_charts?REQUEST=Getcapabilities

http://docs.gina.alaska.edu/tiles/merc.html

Arizona
Metadata: http://imagery.azmap.org/ArcGIS/rest/services
Homepage: http://sco.azland.gov/imagery.htm

Arkansas
Metadata: http://www.geostor.arkansas.gov/ArcGIS/rest/services

California
Metadata: http://atlas.resources.ca.gov/ArcGIS/rest/services

Colorado
No state government web site found yet that offers GIS data via the REST interface or WMS interface. Do you know of any?

Connecticut
State data center:
REST Metadata: http://www.ctecoapp2.uconn.edu/ArcGIS/rest/services/maps

University of Connecticut - MAGIC. Historical maps and more.
WMS information: http://magic.lib.uconn.edu/help/help_WMS.htm
WMS metadata: http://72.248.187.142/wms/wms.exe?request=getcapabilities&service=wms

Delaware
State GIS data streams shut down due to lack of funds

University of Delaware Environmental Monitoring and Analysis Center
Scroll down for WMS URL: http://demac.udel.edu/data/aerial-photography

Florida
http://map.floridadisaster.org/GIS/rest/services

Georgia
No state government web site found yet that offers GIS data via the REST interface or WMS interface. Do you know of any?

Hawaii
No state government web site found yet that offers GIS data via the REST interface or WMS interface. Do you know of any?

Idaho
http://cloud.insideidaho.org/ArcGIS/rest/services

Illinois
No state government web site found yet that offers GIS data via the REST interface or WMS interface. Do you know of any?

Indiana
http://gis.in.gov/ArcGIS/rest/services

Iowa
http://programs.iowadnr.gov/arcgis/rest/services/
https://geonexusr.iowadot.gov/ArcGIS/rest/services

Iowa State University: http://mesonet.agron.iastate.edu/ogc/

Kansas
http://mapserver.kansasgis.org/arcgis/rest/services
http://imageserver.kansasgis.org/arcgis/rest/services

Kentucky
http://kygisserver.ky.gov/arcgis/rest/services

Louisiana
No state government web site found yet that offers GIS data via the REST interface or WMS interface. Do you know of any?

Maine
Scroll down to "Web Mapping Services (WMS)": http://www.maine.gov/megis/maps/

Note: The Maine WMS server does things a little differently. I need to make a modest revision to the Gmap4 code before this data can be displayed.

Example of how to make a WMS GetCapabilities link:
http://mapserver.maine.gov/wms/mapserv.exe?map=c:/wms/orthos.map&request=GetCapabilities&service=wms

Maryland
http://www.mdimap.us/ArcGIS/rest/services/

Massachusetts
GetCapabilities file:
http://giswebservices.massgis.state.ma.us/geoserver/wms?request=GetCapabilities&service=WMS&version=1.1.1

Michigan
http://gis.mcgi.state.mi.us/ArcGIS/rest/service

Minnesota
Covers the 7 metro counties: http://www.datafinder.org/catalog/
http://geoint.lmic.state.mn.us/cgi-bin/wmsll?VERSION=1.3.0&SERVICE=WMS&REQUEST=GetCapabilities

http://deli.dnr.state.mn.us/services.html

http://www.mngeo.state.mn.us/chouse/wms/wms_image_server_specs.html

Mississippi
http://www.gis.ms.gov/arcgis/rest/services

Missouri
http://msdisweb.missouri.edu/ArcGIS/rest/services
http://moimagery.missouri.edu/ArcGIS/rest/services

Montana
http://gisservice.mt.gov/arcgis/rest/services

Nebraska
No state government web site found yet that offers GIS data via the REST interface or WMS interface. Do you know of any?

Nevada
No state government web site found yet that offers GIS data via the REST interface or WMS interface. Do you know of any?

New Hampshire
No state government web site found yet that offers GIS data via the REST interface or WMS interface. Do you know of any?

New Jersey
Summary of metadata:
https://njgin.state.nj.us/oit/gis/NJ_NJGINExplorer/wms_instruct.htm

Metadata:
http://njwebmap.state.nj.us/njimagery?request=GetCapabilities


If you start here:
https://njgin.state.nj.us/NJ_NJGINExplorer/index.jsp

and then click "Map Services" in the left side panel you can likely find a lot more WMS GetCapabilities metadata. This is one of the more obtuse methods for obtaining metadata.

New Mexico
No state government web site found yet that offers GIS data via the REST interface or WMS interface. Do you know of any?

New York
http://gis.ny.gov/gateway/mg/webserv/webserv.html

http://www.broadbandmap.ny.gov/content/web-services.html

North Carolina
http://149.168.87.13/ArcGIS/rest/services/ http://imagery.nconemap.com/arcgis/rest/services

North Dakota
http://ndgishub.nd.gov/arcgis/rest/services

Ohio
No state government web site found yet that offers GIS data via the REST interface or WMS interface. Do you know of any?

Oklahoma
Unfortunately they seem to only be using WMS 1.1.0. See: http://ogi.state.ok.us/ogi/WFS.aspx#GC
Gmap4 supports WMS 1.3.0 and WMS 1.1.1 but does not support the older WMS 1.1.0.

Oregon
http://navigator.state.or.us/ArcGIS/rest/services
http://oregonexplorer.info/imagery/AccesstheImagery/StreamImagery

Pennsylvania
Click link for "Map Services" in left sidebar: http://www.pasda.psu.edu/mapping/default.asp

Rhode Island
No state government web site found yet that offers GIS data via the REST interface or WMS interface. Do you know of any?

South Carolina
No state government web site found yet that offers GIS data via the REST interface or WMS interface. Do you know of any?

South Dakota
http://arcgis.sd.gov/arcgis/rest/services

Tennessee
http://tnmap.tn.gov/arcgis/rest/services

Texas
No state government web site found yet that offers GIS data via the REST interface or WMS interface. Do you know of any?

Utah
No state government web site found yet that offers GIS data via the REST interface or WMS interface. Do you know of any?

Hosted by University of Utah: http://earth.gis.usu.edu/wms/utah?request=getcapabilities&service=wms

Vermont
Look for services that are "MapServer". Gmap4 cannot (yet) display ImageServer or FeatureServer services.
http://maps.vcgi.org/arcgis/rest/services/

Virginia
http://gismaps.vita.virginia.gov/arcgis/rest/services

Washington
Look for the entries that say "MapServer". Gmap4 does not yet support FeatureServer.

http://services.arcgis.com/jsIt88o09Q0r1j8h/ArcGIS/rest/services

Washington State Recreation and Conservation Office (RCO)
http://gismanager.rco.wa.gov/ArcGIS/rest/services

Dept. of Transportation
http://www.wsdot.wa.gov/ArcGIS/rest/services

Dept. of Revenue
http://webgis1.dor.wa.gov/ArcGIS/rest/services

West Virginia
http://services.wvgis.wvu.edu/ArcGIS/rest/services

Wisconsin
No state government web site found yet that offers GIS data via the REST interface or WMS interface. Do you know of any?

University of Wisconsin. Uncheck all boxes except 'Web Mapping Services' and then search. http://www.sco.wisc.edu/wisclinc/findgeodata.php

Wyoming
They appear to have data available via REST but their server keeps throwing an error instead of displaying the metadata.
http://wygl.wygisc.org/wygeolib/catalog/browse/browse.page


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USA other sources for GIS data

The sections REST metadata and WMS metadata explain how to use these links. If you have not yet read those sections, then now would be a good time to do so.

BP Deepwater Horizon well oil spill
Links to meta data: http://gis.aerometric.net/services.htm
Homepage: http://gis.aerometric.net/

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Canada sources for GIS data

The sections REST metadata and WMS metadata explain how to use these links. If you have not yet read those sections, then now would be a good time to do so.

Geobase
Metadata: http://ows.geobase.ca/wms/geobase_en?service=wms&request=GetCapabilities&version=1.1.1
Data descriptions - scroll down: http://www.geobase.ca/geobase/en/wms/index.html
Geobase homepage: http://www.geobase.ca/geobase/en/

Fish and ocean
http://www.pac.dfo-mpo.gc.ca/gis-sig/services-eng.htm

British Columbia
http://www.data.gov.bc.ca/dbc/geographic/connect/index.page?
Metadata: There are several different WMS metadata files that together list a large number of data layers that Gmap4 can display. Use the above link to access these metadata files.

Ontario
http://www.mnr.gov.on.ca/en/Business/LIO/2ColumnSubPage/276201.html (WMS version 1.1.1)
Sample metadata: http://www.lio.ontario.ca/wmsconnector/com.esri.wsit.WMSServlet/wms_legalareas?request=getcapabilities


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Australia source for GIS data

The section WMS metadata explains how to use this link. If you have not yet read that section, then now would be a good time to do so.

A variety of data including contour lines and shading
Metadata: http://www.ga.gov.au/gis/services/topography/Australian_Topography/MapServer/WMSServer?request=GetCapabilities&service=WMS


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Part 4 - Example Gmap4 links

In order for Gmap4 to let you 'click link - see GIS data', the links need to be longer than average. Don't panic. Each of these links can be divided into the following pieces:

1. Gmap4 program code
http://www.mappingsupport.com/p/gmap4.php

2. All Gmap4 parameters except any '&q=', '&markers=', '&rest', '&wms=' parameters
Although the following three parameters are optional, you will likely want to use them when displaying GIS data:
&ll= latitude,longitude for map center
&z= zoom level when map opens
&t= map type (comma separated list). One basemap name (optional) and one or more transparent overlay names.

3. '&markers=' parameter or '&q=' parameter (optional)
The '&markers=' parameter is part of Gmap4's unique map-in-a-link feature and it can be used to put a title on these maps and also used to display multiple KML/KMZ files. Since a map title can include one or more links, sometimes a map title will take up a good part of a Gmap4 link.

4. '&rest=' and or '&wms=' parameters (often more than one)
Each one identifies one GIS server and one or more layers of data hosted on that server.

All '&rest' and '&wms=' parameters need to be at the end of the Gmap4 link.

If the link includes a '&markers=' parameter or '&q=' parameter then it must come right before the first '&rest=' or '&wms=' parameter.

You might also see "%20" in some Gmap4 links. This is one form of computer-speak for a space. Some forum software does not correctly handle links with spaces. Some email software is the same way. By changing each space to "%20" this problem is avoided.

Moral of the story: Don't be spooked by these long links. Simply divide them into pieces as shown above and you will see what is going on.

Example Gmap4 links showing GIS data - USA

Tip for smartphone and tablet users. To save any Gmap4 link as a bookmark in the browser on your smartphone or tablet, email that link to yourself. Then open that link with your mobile browser and save it as a bookmark. I know this works on an iPhone 4s using iOS 6.1.3 and Safari.

USA basemap - two versions

This map has two additional basemaps that are added via "&rest=" parameters. When the map opens it shows most of the USA (on a desktop size screen) and has a background that is shaded to help show elevation changes. The other new basemap is the same except the background shows aerial photos. The data for both of these basemaps is already stored as tiles on the GIS server. This means that the maps display quickly. However, these pre-made tiles are only designed to be displayed at a maximum zoom of 15 (Google scale shows 200m/1000ft). If you zoom in further then the data becomes fuzzy.

This is similar to the "US Topo" product that the USGS is using to replace the traditional paper 1:24,000 scale topographic maps.

http://www.mappingsupport.com/p/gmap4.php?ll=38.539036,-99.11745&z=5&t=USA_basemap_shaded&coord=off&rest=http://basemap.nationalmap.gov/ArcGIS/rest/services/USGSTopo/MapServer?name=USA_basemap_shaded&rest=http://basemap.nationalmap.gov/ArcGIS/rest/services/USGSImageryTopo/MapServer?name=USA_basemap_aerial

Boundary Water Canoe Area, Minnesota

This map shows the boundary (GIS data), entry points (KML file #1), portages (KMl file #2) and campsites (txt file) that are open as of June 2013. Click a campsite symbol for the coordinates. You can also zoom in and then click Menu == > Label On/Off. A label holding the coordinates will appear next to each campsite. If you zoom in a bunch then you will see lines and arrows showing the direction the water is flowing (this data looks real nice on the "t4 Topo High" basemap). When the map opens, color infrared aerials are displayed. You can display "1-foot" aerials that have better resolution that Google's aerials. Anything that looks like a space in the link is actually an underline character.

Note: The GIS layers for this map are specified in the 'txt' file that you see in the link. You can download that txt file and look at its contents.

http://www.mappingsupport.com/p/gmap4.php?t=Color_infrared,Water_flow_direction,Boundary&q=https://sites.google.com/site/gmap4files/p/recreation/bwca_campsites.txt

Detailed boundary for land owned by the USA

This example shows very detailed boundary lines for most of the federally owned land in the USA. This includes national forest land, Bureau of Land Management holdings and other land. This map opens centered near Denver but can display data for all of the USA.

http://www.mappingsupport.com/p/gmap4.php?ll=39.740986,-104.996338&t=h,Public_land&z=8&wms=http://wildfire.cr.usgs.gov/ArcGIS/services/geomac_dyn/MapServer/WMSServer?name=Public_land&layers=1&transparent=true

MGRS Grid - USA National Grid

Here is a map that displays a grid overlay that is both the MGRS grid and the USA National grid. MGRS stands for Military Grid Reference System. Many people with military experience know about the MGRS grid and many governmental agencies use the same grid system but call it the USA national grid or USNG. Keep zooming in for more detail in the grid.

http://www.mappingsupport.com/p/gmap4.php?tilt=off&ll=38.379933,-100.682617&z=5&t=h,National_grid&rest=http://maps1.arcgisonline.com/ArcGIS/rest/services/NGA_US_National_Grid/MapServer?name=National_grid&layers=0-110&transparent=true

Forest fires - Current boundaries

The following map displays the (1) boundaries for most land owned by the federal government (USFS, BLM, etc), (2) the most recent forest fire perimeters added to the GIS server and (3) one green symbol for each fire. When the map first opens the green symbol might cover up the fire perimeter.

To see the high resolution topographic map, zoom in so the scale in the lower left says 1 mile and then change the basemap to "t4 Topo High".

http://www.mappingsupport.com/p/gmap4.php?ll=37.544578,-99.140625&z=5&t=m,Public_land,Fire_perimeter,Fires&wms=http://wildfire.cr.usgs.gov/ArcGIS/services/geomac_dyn/MapServer/WMSServer?name=Public_land&layers=1&transparent=true&wms=http://wildfire.cr.usgs.gov/ArcGIS/services/geomac_dyn/MapServer/WMSServer?name=Fire_perimeter&layers=23&transparent=true&wms=http://wildfire.cr.usgs.gov/ArcGIS/services/geomac_dyn/MapServer/WMSServer?name=Fires&layers=24&transparent=true

If you always want the map to open and be zoomed in on a specific fire then you will need to change the ll and z parameters to suit your needs. Just make the map look the way you want it to look and then click/touch Menu ==> Link to this map. Copy the link you see. That link will reproduce the map that is on your screen.

If you want to see information about other data layers related to forest fires, here is a link to the GetCapabilities metadata:
http://wildfire.cr.usgs.gov/ArcGIS/services/geomac_dyn/MapServer/WMSServer?request=GetCapabilities

Earthquake risk

The colors on this map show the relative amount of risk for an earthquake. If you zoom in on this map then you will see the county boundaries. If you zoom in two more steps then you will see the county names.

The "&markers=" parameter is used to put a title on the map. The title includes a link to a png file that displays a map legend.

http://www.mappingsupport.com/p/gmap4.php?ll=38.466005,-99.056641&z=5&t=Seismic_hazard,Counties,States&markers=title=<b>Earthquake%20Risk<br%20/><a%20href=http://webservices.nationalatlas.gov/wms?version=1.3.0&service=WMS&request=GetLegendGraphic&sld_version=1.1.0&layer=seihaz&format=image/png&STYLE=default%20target='_blank'>Legend</a></b>&wms=http://webservices.nationalatlas.gov/wms?name=Seismic_hazard&layers=seihaz&rest=http://services.nationalmap.gov/ArcGIS/rest/services/govunits/MapServer?name=Counties&layers=3,13&transparent=true&wms=http://webservices.nationalatlas.gov/wms?name=States&layers=states&transparent=true

USA coastal charts

This map can display all of the USA costal nautical charts prepared by NOAA. According to NOAA, these electronic charts will be updated once every two weeks and are not to be used for navigation. Now would also be a good time for you to review Gmap4's terms of service. In other words, if you put your boat on the rocks, don't blame NOAA and don't blame me.

When this map opens it shows the detailed 'Harbour' chart for the mouth of the Columbia River. Be patient. Some 'tiles' have a lot of detail and it may take a few seconds for all the data to appear on your screen. These charts come in several different scales that you can display if you open the 'map type' menu. Since each scale of chart is hosted on a different GIS server, there are a number of &wms= parameters in the Gmap4 link. Each series of charts looks the best at a different zoom level as follows:

Charts_Overview, zoom level 10 (scale shows 10km/5mi), black box when zoomed out.
Charts_General, zoom level 11 (scale shows 5km/2mi), brown box when zoomed out.
Charts_Coastal, zoom level 12 (scale shows 2km/2mi), green box when zoomed out.
Charts_Approach, zoom level 14 (scale shows 500m/2000ft), blue box when zoomed out.
Charts_Harbour, zoom level 15 (scale shows 100m/1000ft), pink box when zoomed out.
Charts_Berthing, As of July 10, 2013 there is only a small amount of data near New Orleans.

If you would like to see the zoom level, rightclick the map. Mobile users can touch Menu ==> "Link to this map" and look for the "&z=" parameter.

http://www.mappingsupport.com/p/gmap4.php?ll=46.257257,-124.043198&z=14&t=m,Charts_Harbour&wms=http://encdirect.noaa.gov/arcgis/services/encdirect/enc_overview/MapServer/WMSServer?name=Charts_Overview&layers=1-96&transparent=true&wms=http://encdirect.noaa.gov/arcgis/services/encdirect/enc_general/MapServer/WMSServer?name=Charts_General&layers=1-137&transparent=true&wms=http://encdirect.noaa.gov/arcgis/services/encdirect/enc_coastal/MapServer/WMSServer?name=Charts_Coastal&layers=1-193&transparent=true&wms=http://encdirect.noaa.gov/arcgis/services/encdirect/enc_approach/MapServer/WMSServer?name=Charts_Approach&layers=1-244&transparent=true&wms=http://encdirect.noaa.gov/arcgis/services/encdirect/enc_harbour/MapServer/WMSServer?name=Charts_Harbour&layers=1-239&transparent=true&wms=http://encdirect.noaa.gov/arcgis/services/encdirect/enc_berthing/MapServer/WMSServer?name=Charts_Berthing&layers=1-107&transparent=true

Of course all the Gmap4 features continue to work when GIS data is being displayed. Would you like to display a UTM grid on top of the chart? No problem. Use the Menu button to turn on UTM. Want to find a certain location? Try Menu ==> Search. When you are in an area covered by these charts and there is cell coverage, try opening this link with the browser in your smartphone or tablet and then touch Menu ==> My location. (Be sure the GPS in your smartphone or tablet is turned 'on'.)

To display your GPS track on the chart use the "&q=" parameter and place it before the first "&rest=" or "&wms=" parameter. Then open the revised map link, turn off the charts and zoom in on your GPS track. Pick the chart you want to have displayed when the map opens. Now click (or touch) Menu ==> Link to this map. Copy that link and delete the &ll and &z parameters. You now have a link that will start Gmap4, automatically center the map on your GPS track and display the type of chart you selected.

Index to USGS topographic maps

The following link shows the topo map index for the Sierra Nevada mountains in California near Lake Tahoe.

http://www.mappingsupport.com/p/gmap4.php?ll=39.068781,-120.226135&z=10&t=m,topo_index&wms=http://services.nationalmap.gov/arcgis/services/map_indices/MapServer/WMSServer?name=topo_index&layers=1,6&transparent=true

Opps! Whoever built this data used a poor font for the map names. If you have trouble reading the names, then change the basemap to "all white basemap".

Q: How can this map help you?
A: Assume you are planning a hiking trip and want to take paper topographic maps along. Turn off the map index so it is not distracting. Click Menu ==> Draw and Save. Click Continue. Click along the trail you plan to hike. Turn the map index back on. Change the base map to "All white basemap". You can now easily read the names of the topographic maps that cover the area where you will be hiking.

If you want the map to open and automatically show the index for a certain area, simply make the map look the way you want it to look on your screen and then click Menu ==> Link to this map. The link you see will reproduce the map you see on your screen.

US Army Corps of Engineers

This map shows land that involves the US Army Corps of Engineers. This includes bombing ranges, missle sites and a lot more. Zoom in for labels.

http://www.mappingsupport.com/p/gmap4.php?ll=37.398715,-99.033123&z=5&t=m,USACE_boundary&wms=https://rsgisias.crrel.usace.army.mil/cgi-bin/wms/publicfuds_wms?name=USACE_boundary&layers=fudspoly&transparent=true

Lake and river related overlays

This example shows you three different ways to make a Gmap4 link that shows the same data. Each of these three ways gives the person viewing your map a different amount of control for playing with the data. There is no one right answer. Use the approach that works best for the story you want your map to tell.

These maps all display the same 5 data layers that are hosted on the same WMS server.

Option 1 - All five data layers in one wms parameter

A single "&wms=" parameter identifies all five layers. The "layers=" parameter lists "hucs" first since this data shows different solid colors for watersheds and is actually not transparent. Therefore the 'hucs' layer must go on the bottom of the stack so it does not cover up any of the data from the layers that really are transparent.

If you use this option then you will only be able to see the truly transparent layers on top of the "hucs" data.

http://www.mappingsupport.com/p/gmap4.php?ll=37.544578,-99.140625&z=5&t=Water_data&wms=http://webservices.nationalatlas.gov/wms/water?name=Water_data&layers=hucs,lakesrivers,dams,surface,wrdgage&transparent=true

Recall that Gmap4 always displays one basemap. By definition a layer that is defined as transparent is not a basemap. When the "&t=" parameter only points to one or more layers that are defined as transparent in the Gmap4 link, then the default basemap is "All white basemap". When there is no "&t=" at all in the Gmap4 link then the default basemap is "t1" which is the Google terrain map.

Option 2 - Using two wms parameters

This option uses two "&wms=" parameters. The first one identifies the "hucs" data and does not identify this layer as transparent. Since the default is "transparent=false", this first "&wms=" parameter defines "hucs" as an additional basemap.

This option lets you look at the four transparent layers on the "hucs" basemap or on top of any other basemap. But all transparent overlays are either on or off.

http://www.mappingsupport.com/p/gmap4.php?ll=37.544578,-99.140625&z=5&t=m,HUCS,Water_data&wms=http://webservices.nationalatlas.gov/wms/water?name=HUCS&layers=hucs&wms=http://webservices.nationalatlas.gov/wms/watername=Water_data?&layers=lakesrivers,dams,surface,wrdgage&transparent=true&format=image/png

Also notice that the above link says "&t=m,HUCS,Water_data". Both "m" (Google roadmap) and "HUCS" are basemaps. But Gmap4 only displays one basemap at a time. When "&t=" specifies more than one basemap it is the first basemap that is displayed when the map opens. For that reason, the map opens with the Google roadmap ('m') instead of the HUCS basemap.

Option 3 - Six wms parameters, each one calls just one data layer

This option uses five "&wms=" parameters for the water data plus a 6th "&wms=" parameter to add an outline of the states. The basemap is the "hucs" layer. Since the "hucs" layer only has data for the USA, the rest of the map is blank.

The five transparent overlays can each be turned on/off. When you turn an overlay on it is added to the map at the top of the stack. A number in front of an overlay indicates that (1) the overlay is on and (2) shows its position in the stack. Overlay #1 is on the bottom of the overlay stack. To restore the original stacking order, turn all overlays off and then turn them all back on using the last two menu options.

http://www.mappingsupport.com/p/gmap4.php?ll=37.544578,-99.140625&z=5&t=HUCS,Lakes_Rivers,Dams,NAWQA_sites,Stream_Gages,States&wms=http://webservices.nationalatlas.gov/wms/water?name=HUCS&layers=hucs&wms=http://webservices.nationalatlas.gov/wms/water?layers=lakesrivers&transparent=true&format=image/jpeg&name=Lakes_Rivers&wms=http://webservices.nationalatlas.gov/wms/water?name=Dams&layers=dams&transparent=true&format=image/png&wms=http://webservices.nationalatlas.gov/wms/water?name=NAWQA_sites&layers=surface&transparent=true&format=image/png&wms=http://webservices.nationalatlas.gov/wms/water?name=Stream_Gages&layers=wrdgage&transparent=true&format=image/png&wms=http://webservices.nationalatlas.gov/wms?name=States&layers=states&transparent=true

Switch the basemap for the above map between "HUCS" and "All white basemap" and watch what happens.

Also, the above map will look the same way when it opens if you write:
&t=HUCS,Lakes_Rivers,Dams,NAWQA_sites,Stream_Gages,States
or
&t=Lakes_Rivers,Dams,NAWQA_sites,Stream_Gages,States,HUCS

In both cases the first basemap listed in the 't' parameter is HUCS and so that basemap will be displayed when the map opens.

Remember, to understand what is going on in one of these long Gmap4 links, simply break the link into pieces as shown at the start of these examples.

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Example Gmap4 links showing GIS data - Canada

Canada - Arrows showing direction of water flow

This map shows a vector topographic map for a random spot in Quetico Provincial Park, Canada, and arrows showing the direction of stream flow.

http://www.mappingsupport.com/p/gmap4.php?ll=48.439166,-91.383762&z=13&t=t5,Flow_arrows&wms=http://ows.geobase.ca/wms/geobase_en?name=Flow_arrows&layers=nhn:network:FLOWDIRECTION_1&transparent=true

Index of the 1:50,000 scale Canada topographic maps

This index covers all of Canada. One way to change the map to a different spot is to use Menu ==> Search.

http://www.mappingsupport.com/p/gmap4.php?ll=45.943511,-73.696289&z=8&t=t5,Topo_outline,Topo_name&wms=http://ows.geobase.ca/wms/geobase_en?layers=reference:nts&transparent=true&name=Topo_outline&wms=http://ows.geobase.ca/wms/geobase_en?name=Topo_name&layers=reference:nts:annotation_50k&transparent=true

British Columbia map

The following map has three layers that show water courses, water flow arrows and the 20 meter contour lines. The map opens centered near Whistler and shows the Google aerial together with these three layers.

http://www.mappingsupport.com/p/gmap4.php?ll=50.11125,-122.978296&z=14&t=s,Water_course,Flow_arrows,BC_topo&wms=http://openmaps.gov.bc.ca/mapserver/base3?name=Water_course&layers=TWTR_LINES&transparent=true&version=1.1.1&wms=http://ows.geobase.ca/wms/geobase_en?name=Flow_arrows&layers=nhn:network:FLOWDIRECTION_1&transparent=true&wms=http://openmaps.gov.bc.ca/mapserver/base3?name=BC_topo&layers=TCTR_LINES&transparent=true&version=1.1.1

Patent and unpatent crown land - Ontario only

The following map displays patent and unpatented crown land and patent land. OK, time for me to 'fess up. I do not have a clue what any of that means. But the map looks really cool and if you live in Ontario you might be interested.

http://www.mappingsupport.com/p/gmap4.php?ll=44.649605,-79.039764&z=11&t=t5,Land_type&markers=title=<div%20style="font-weight:bold;">Crown%20Land%20and<br%20/>Patent%20Land<br%20/>Ontario%20Only<br%20/><a%20href="http://www.mnr.gov.on.ca/en/Business/LIO/2ColumnSubPage/276201.html"%20target="_blank">Data%20source</a><br%20/></div>&wms=http://www.lio.ontario.ca/wmsconnector/com.esri.wsit.WMSServlet/wms_legalareas?name=Land_type&layers=CL_UNPATENTED,CL_PATENT_LAND,PATENT_LAND&transparent=true&version=1.1.1

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