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Gmap4 - Enhanced Google Map viewer with topographic maps

Posted: Fri Sep 03, 2010 1:23 pm
by Joseph
I am the author of Gmap4 which is a 100% free no-ads full-screen enhanced Google Map viewer. It includes detailed topographic maps (courtesy of" onclick=";return false;) for the USA and Canada. Gmap4 runs entirely online. There is nothing to buy, nothing to download, nothing to install.

In addition to surfing topographic maps, you can also view data from the following types of files: GPX, KML, KMZ, TPO & Google MyMap files.

You do need to place your GPX, KML, KMZ and TPO files online before they can be displayed by Gmap4. The easiest/fastest way to place files online is via Google Sites (free). Don’t be shy. You will find hand-holding-step-by-step instructions in the Gmap4 Help file.

Here is the general recipe for building a URL to display a data file with Gmap4 (do not include the quotes, these are not a real links):
For data files showing locations in the USA or Canada:
' ... _your_file'
For data files showing other locations:
' ... _your_file'

Below is a link to the Gmap4 homepage. Check out the 'Examples' button and the Quick Start section of the 'Help' file." onclick=";return false;

Finally, if you run a website where people file trip reports you could consider allowing Gmap4 to run in an iframe. Your users could include a 100% free interactive map with their GPS track and waypoints along with the rest of their trip report. Gmap4 has a liquid design and will look decent in an iframe down to 400px by 400px. For examples: Search the Trip Report forum at" onclick=";return false; for 'Gmap4'.


Re: Gmap4 - Enhanced Google Map viewer with topographic maps. F

Posted: Sat Sep 04, 2010 6:13 pm
by richapple
Hey, this is pretty durn cool... I only tried the find latitude,longitude via Google Maps, then fed the ll= values to the php script, and wham-bam can toggle between a MyTopo offering and what's at Google Maps. Thanks, and I will explore more later.

One question: Since you must have some insight and knowledge in this neighborhood, do you know why Google's "terrain" suddenly dumped the trails it used to show? That was a very cool feature that was at least there for some locations that suddenly disappeared.

(None of this beats an actual Harrison Topo Map to have in your paws while backpacking, though. In my humble opinion...)

Again, thanks, and I hope this effort of yours gets used and appreciated...

Rich Apple

Re: Gmap4 - Enhanced Google Map viewer with topographic maps. F

Posted: Sun Sep 12, 2010 7:37 pm
by Joseph
Thanks for the kind words.
I have no idea why the trails on Google Terrain view went away

Re: Gmap4 - Enhanced Google Map viewer with topographic maps. F

Posted: Tue Sep 14, 2010 12:33 pm
by fishmonger
I really like this interface. One thing I ran into was that there seems to be a limit in data filesize. I've tried loading a big single log file of all days of my trip combined, but the screen stayed white forever. then I switched to loading them in a multi-file mode as instructed on your site, but even then the limit was about 5 days worth of logs. I could not add another until I dropped others from the xml file. I really would like to display the entire Muir Trail hike on one map, but I assume I have to drop the resolution in the log files to a level I don't really like. Is there a hard limit on file size, or could this be a bug? Would it help if I ditched time and elevation data from the GPX files?

Re: Gmap4 - Enhanced Google Map viewer with topographic maps. F

Posted: Wed Sep 15, 2010 7:59 pm
by Joseph
I surfed for files showing the GPS track of the Muir trail. The first one I found was a KML file but it did not work - not sure why. The second one I found was a GPX file and it worked fine: ... _Trail.gpx
To see the detailed topographic view: zoom in then click (upper right) Terrain ==> MyTopo.

I found both files here:" onclick=";return false;

Yes, Google does impose limits on the size of the data file that can be displayed. This page ... pport.html says the limits are:
"Maximum fetched file size (raw KML, raw GeoRSS, or compressed KMZ) 3MB
Maximum uncompressed KML file size 10MB
Maximum number of Network Links 10
Maximum number of total document-wide features 1,000"

1 GPS track is only 1 "feature".

If you use Gmap4 to view a GPX or TPO file, then Gmap4 first converts that file to KML and then the above limits apply.

Re: Gmap4 - Enhanced Google Map viewer with topographic maps. F

Posted: Thu Dec 23, 2010 2:31 pm
by Joseph
Gmap4 has acquired some new features since my prior post. Remember, Gmap4 is a 100% free no-ads map viewer that can display detailed topographic maps. There is nothing to download or install.

1. A powerful search feature has been added. Click Menu ==> Search. You can search on:
* Addresses
* Names of places and natural features
* Latitude Longitude (Geocache format and many others)

Here’s an interactive map of the world: ... 8&t=t1&z=2" onclick=";return false;.
Depending on what you are searching for, it may help if you include the name or abbreviation for the state/province/region. If you are searching for something in the USA or Canada then you can see the detailed topographic map by clicking Terrain ==> MyTopo.

2. Maps can be printed. In the menu bar for your browser click File ==> Print preview.

3. An icon can be placed at the center of the map. Here’s an example. ... 4&icon=pgs" onclick=";return false;

4. It is easier to get a copy of the URL that will reproduce the map you see on your screen. Click Menu ==> Map URL.
That URL can be used in a trip report, e-mailed, posted on a website, etc.

For more information please see the Gmap4 homepage where you will find examples, a change log and a detailed Help file." onclick=";return false;

Joseph - Gmap4 author

Re: Gmap4 - Enhanced Google Map viewer with topographic maps. F

Posted: Sun Jan 02, 2011 6:39 pm
by Joseph
Gmap4 has been updated to version 1.8.3

The present-day magnetic declination for the map center is now always displayed in the lower right corner. This value is produced using software from" onclick=";return false; combined with data from" onclick=";return false;.
Since the magnetic declination is always changing, the older value printed on maps can be wrong by several degrees.

I also updated my links page to show (1) reviews of Gmap4 and (2) sites that are already using Gmap4 to produce online interactive maps." onclick=";return false;

Finally, if you are interested in the search feature and/or print feature, please check the ‘Help’ file (and use the Table of Contents) to be sure you have seen the most recent info on those features." onclick=";return false;

The link below will display a world map. To test-drive the search feature click Menu==>Search. ... 5&t=t1&z=2" onclick=";return false;

Joseph - Gmap4 author

Re: Gmap4 - Enhanced Google Map viewer with topographic maps. F

Posted: Sun Jan 02, 2011 9:44 pm
by rlown
guess there's no way you can get google to put back the lake names on GE.. cuz, losing that really sucked. Seems they put back peak names, but not the lakes.. I've already complained to them on their board about it.. Seems several are really ticked off about it.

Re: Gmap4 - Enhanced Google Map viewer with topographic maps. F

Posted: Sun Jan 02, 2011 10:25 pm
by Joseph
The good news is that there are other databases that do include lake names. I plan to add one or more additional search tools so lakes can be found. Not sure when I will get it done but it is certainly on the list.

Re: Gmap4 - Enhanced Google Map viewer with topographic maps. F

Posted: Wed Jan 19, 2011 5:24 pm
by Joseph
Gmap4 has been updated to version 1.9.1 dated January 17, 2011. This version adds support for UTM coordinate grids. All UTM support in Gmap4 uses the WGS84 datum. This UTM support works worldwide. For more info on UTM coordinates see: ... ate_system" onclick=";return false;

(Pay back time: When you visit other outdoor-related forums, please do a search and see if Gmap4 has been mentioned. If not, it would just take a moment for you to pass the word along. Also, are you doing the social network thing? Consider saying something nice about Gmap4.)

Here’s a map of Grand Canyon Village with a UTM grid. ... &coord=utm" onclick=";return false;

To toggle UTM support on and off, click Menu ==> UTM On/Off. If UTM is ‘on’ then Gmap4 gives you UTM information in three ways:

1. A UTM grid is displayed. This UTM grid is displayed on both the MyTopo topographic maps (USA and Canada) and the standard views (aerial, etc) provided by Google Maps.

2. The lower right corner of the screen will always show the UTM zone and UTM coordinates for both the cursor and map center.

3. You can get the UTM zone and coordinates for any point on the map by right-clicking that point.

Things to keep in mind

You can build you own map links by using URL parameters. If you want your map to appear on the user’s screen and already have UTM turned on, then add this URL parameter: &coord=utm

Here is a comparison:
With UTM on ... &coord=utm" onclick=";return false;
With UTM off (default) ... k.kml&t=t2" onclick=";return false;

If you zoom out far enough then you will not see a UTM grid. Instead you will only see vertical red lines which mark the edges of the UTM zones.

UTM grid lines that are near the edge of their zone often appear curved when displayed using the map projection used by Google Maps. The grid lines in the adjoining zone will curve in the opposite direction. For example, the next map is centered near Lake Tahoe. The red line marks the edge of adjoining UTM zones. Double click each side of the red line (this changes the map center) and watch the UTM grid lines change. The grid lines are calculated based on the UTM zone that contains the center of the map. ... &coord=utm" onclick=";return false;

Some MyTopo topographic maps already have a UTM grid printed on them. Caution! Some of those printed grids are based on the older datum NAD27. Those older grids will have a uniform offset from the grid displayed by Gmap4 which is based on datum WGS84 . For example: Here is a map showing part of the Alpine Lakes Wilderness area in Washington State where the MyTopo maps have a UTM grid based on the WGS84 datum. Click Menu ==> UTM On/Off and you will see the faint UTM grid printed on the map: ... &coord=utm" onclick=";return false;

By contrast, here is a map showing part of the Yosemite Valley area in California, where the MyTopo maps have a UTM grid based on NAD27. Note the uniform offset between the two sets of grid lines. ... &coord=utm" onclick=";return false;

Usually (but not always) the different zoom levels use a different scale for the UTM grid. To learn the grid scale, compare the cursor coordinates (lower right corner) as you point to adjacent grid lines. If you want to know the zoom level, right click the map.

Maps with UTM grid lines can be printed. File ==> Print Preview

If you know of any other map viewing software that can display the MyTopo topographic maps along with a UTM grid, I would enjoy knowing about it.

Future UTM improvements

There are different methods for putting labels on the grid lines. I am pondering what will work best.
Another possible improvement is to let the user change the line width, color and/or spacing.
Other ideas?

Next Gmap4 update

Bad news: The ‘Search’ feature of Gmap4 no longer works very well for placenames. This feature uses Google’s ‘geocoding’ service on the backend. OK, I admit it. Gmap4 was pushing the envelope in its use of that service. Whoops - Google pushed back. Guess who won? I will add a second search tool that is designed to work well with placenames.

Good news: The existing ‘Search’ feature of Gmap4 still works fine for searching on (1) anything related to addresses including names of many settlements that no longer exist and (2) any reasonable way to write a latitude/longitude pair.

Finally, if you find Gmap4 to be useful I hope you can take a moment and do some ‘pay-back’ by letting other people know about it.

Joseph - Gmap4 author