Gmap4 = Google maps + High resolution topo maps + more


New member
(I checked in with the admins first and got the OK to post.)

Everyone likes great maps, right?

is an enhanced Google Map viewer that can display high resolution topographic maps. These maps are based on new scans that have eye-popping quality and cover the USA except for a few states that are not quite ready yet. Here’s an example showing Cinnamon Pass, Colorado:,-107.538008&t=t4&z=15

Note that this topo map (1) is very high resolution - the paper map was scanned by the USGS at 660 pixels per inch, (2) does not have any watermarks on the map ‘tiles’ and (3) does not have any ads. At the present time, there is only one other site on the planet that is displaying these hi-res topo maps in a seamless interface.

Did I mention that you can vary the hill shading on these hi-res maps? Menu ==> Hill shading

Gmap4 also displays the medium resolution MyTopo maps and the low resolution Terraserver maps (now called Microsoft Research Maps). You can do your own quality comparison.

Gmap4 is online software that runs in your browser. There is nothing to buy, nothing to download, nothing to install. Gmap4 will run on most browsers in your phone, iPad, iPod, notebook, laptop, desktop, etc. Gmap4 is not a ‘native’ app. Instead, it is a browser app. Note that the browser does have to be online to the internet. For offline maps consider software like Overland Navigator.

Q: What can you do with Gmap4 besides look at drop dead gorgeous topo maps?
A: A bunch!

I recently added a trip planning feature (Menu ==> Make a map) so you can click the map to make a GPX file that you can load into many (not all) handheld GPS units. Then, when you get back from your trip you can use Gmap4 to display your GPS track.

One of the main features of Gmap4 is its ability to display data files that are hosted online almost anywhere. If you want to put your own data files online but lack your own website to host those files, then just use Google Sites. It is free, easy and it works. The Gmap4 ‘Help’ file has step-by-step instructions for uploading your files to Google Sites. Gmap4 can display GPX, KML, KMZ, TPO and Google MyPlaces files. It can also display a delimited text file format that I designed. Note that you cannot (yet) display files straight from your harddrive. You first have to put your files online.

For example, the following map shows a GPS track for the Mojave Road. To see the topographic maps, first zoom in anywhere and then click (in the upper right corner) Hybrid ==> t4 Topo high.

Another key feature is the ability to share your map with others. If you click Menu ==> Show map URL, then a URL will appear in the message window. You can copy that URL and use it in a forum post, email, blog, website, etc. Whoever clicks that URL link will see the exact same map on their screen.

You can also:
* Automatically center the map on your current location (works best in mobile browsers)
* Display a UTM grid
* Get the current magnetic declination
* Search
* Get directions (the route is draggable)
* Print
* And more

There is no cost for using Gmap4 for non-commercial use. It is simply my way of ‘paying it forward’. But with that said, if you like the new high resolution topographic maps please consider making a donation (Menu ==> Donate) to help offset the hosting cost of that data. You can read more about these new topo maps in the CalTopo section of the Gmap4 ‘Help’ file.

The Gmap4 homepage has a new user FAQ, examples, a detailed pdf Help file, a links page with more examples, a page with the latest beta code and a bit about me.

Gmap4 homepage:
MappingSupport homepage:


Joseph, the Gmap4 guy
Redmond, WA


Expedition Leader
Interesting idea. Any plans to make this usable on an whiles it's it's limited storage capacity while in remote locations (I.e. w/out access to any wireless networks)?



New member
Alas, it is not technically possible for Gmap4 to work offline. Gmap4 does its magic by using the Google map API (application program interface). That API requires the browser to be online to the internet.

Although Gmap4 will not work when you cannot connect to the internet, you may find it useful for trip planning and for posting in forums like this one. In my first post I showed an example of a map with no data at all (Cinnamon Pass) and a map displaying a data file (Mojave Road).

Gmap4 can also produce a third type of map. This type of map has one symbol at the center of the map and may help when you want to talk about one specific spot. Someone posted these Michigan Upper Peninsula coordinates in a thread here awhile back: 46.63108,-87.50803
If you build a Gmap4 URL like so:,-87.50803&t=t4&z=15&symbol=prs
then you will get a map with a small red paddle at those coordinates. Here is a clickable version of the above URL:,-87.50803&t=t4&z=15&symbol=prs

The "t" parameter controls the map type that will be displayed when the map opens. The standard Google map types work anywhere in the world. If you have GPS data for anywhere in Asia, Africa, etc, you can display that data with Gmap4 and the standard Google map types. The following map shows waypoints at various tourist spots in Africa. Click the symbols for more info. I found this data file with a Google search.

If you want topographic maps (1:50,000) for Canada, then checkout the "t2 My Topo" map type.

To read more about the allowable URL parameters, please download the Help file and see p.31.

Joseph, the Gmap4 guy

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New member
Very nicely done!
Am looking forward to checking out the various features you have included. Especially interested in the option to incorporate the clickable photo thumbnails on a map.
Additionally, I think your help file is very well written and easy to understand with great examples.
Will probably use Gmap4 to layout routing, GPX files, for an extensive trip in the Arizona strip next spring.
Thanks for all the work Joseph.


New member
Thanks for the kind words.

Please note that Gmap4 will work on most phones, iPads, iPods, notebooks, laptops and desktops. This is possible because Gmap4 is a browser app. However, your browser must be online. If you browser cannot get online, then Gmap4 will not work.

Here is an easy way to start Gmap4.

Simply use your browser and do a search for 'Gmap4'. In both Google and Bing, the first 'hit' is the Gmap4 homepage. Look right below the homepage title were it says "Start Gmap4". Click that link and Gmap4 will start and display the default map.

If you want to use Gmap4 on your phone then I recommend that you try the latest beta code which has a much improved interface for small screens. To easily launch the beta code, browse to the Gmap4 homepage and then look at the menu bar near the top of that page. Click the "Beta" button in the menu bar and then click the first link on the beta page. If you did that with the default browser in your phone, iPod or Blackberry, then Gmap4 should start and automatically display the interface (i.e. "skin") for small screens.

Also, the beta code has an improved feature to find your location. Click Menu ==> My location. This will use some combination of cell towers, wi-fi hotspots and any GPS chip in your device. If you might be close to a wi-fi hotspot, then make sure your wi-fi is 'on'. If your device has a GPS chip, then double-check to make sure it is 'on'.

Gmap4 is based on the Google map API (application program interface). Google states that this API supports the following browsers:
IE 7.0+ (Windows) *
Firefox 3.0+ (Windows, Mac OS X, Linux)
Safari 4+ (Mac OS X, iOS)
Chrome (Windows, Mac OS X, Linux)
BlackBerry 6
Dolfin 2.0+ (Samsung Bada)
Other browsers may or may not work.

The "My location" feature in the beta code only works on newer browsers. I need to make a list of those.

Joseph, the Gmap4 guy

Jay H
Nice work Joseph! Keep up the good work.
The My Location feature works on my Motorola Droid Bionic running Ginger Bread and the stock browser. Cool feature.

This thing works very well and I am most impressed. I am also
very impressed with Matt - caltopo. The new hi res scans are what takes this proect to another level. I will contacting Matt and the maker of BackCountry navigator today. Matts data in Backcountry navigator for off line use and you slick web use for online would be awesome. I think the caltopo maps will work in back country navigator but I want to clear it with Matt first. if it this does work it will be amazing and may also serve as a way to get Matt some funding for continuing to host this great data.


New member
Recently Gmap4 was updated to version 4.1 and now includes a unique map-in-a-link feature that is worth mentioning. Anyone can now make a custom map and save their data right in a Gmap4 link. You do not need to save your data in a separate file such as a GPX or KML file. This may be the easiest and faster way for you to make a custom online topographic map.

To try out this feature:
1. Click Menu ==> Draw and Save
2. Click the map a few times to set draggable symbols and draw a line
3. Rightclick any symbol and select “Gmap4 display long link”

You can copy the link that is displayed, paste it into a new browser address bar, hit enter and your custom map will be displayed.

This feature also works on your iPhone, iPad, android and other mobile device. Remember, Gmap4 is a browser app and your browser has to be online. After you tap the screen to set some draggable symbols then tap a symbol and select “Action Menu”. The list of actions include two different ways to save a Gmap4 link that includes your data.

More information on this map-in-a-link feature can be found in the following three places.

1. What’s new page
Note the tip about deleting the ll and z parameters from your Gmap4 link.

2. Example page
Scroll down to the section titled “Your map data saved in the Gmap4 link”. The examples range from basic to advanced and give you a quick way to see some of the kinds of maps you can make with this feature.

3. Help file
You can download the PDF file and search it (control-f) for the section titled “Make a custom map with Gmap4 and save it”.

Joseph, the Gmap4 guy
Redmond, WA