Gmap4 is the free online mapping tool that I use for planning hike, backpacking, and bushwhacking trips. I like it because it has some of the most accurate digital maps available online and lets me rapidly compare different maps from several different sources. That is probably the most important feature for me because so many free and commercial digital online maps are so out of date, a problem I’ve written about previously. Being able to compare older ‘historic’ maps, aerial and satellite images, and up-to-date digital maps in one tool helps me determine the best route for my hikes. (I still refer to local printed maps, which are still the most up to date, but harder to plan a route with).
But there are many other features about Gmap4 that make it very attractive for collaborative trip planning and sharing your maps with other people, including the following key capabilities:
- Display grid lines
- Display lat/lon or UTM coordinates
- Display current magnetic declination
- Read and display data from KMZ, KML, GPX, TPO, TXT, and Google MyPlaces files
- Save GPX files
- Change the amount of hill shading
- Route sharing using hyperlinks only – no files or applications needed!
Gmap4 provides users with a wide collection of different maps to choose from, including:
- Street map from Google
- Aerial photo from Google
- Aerial plus street names from Google
- Aerial photo from U.S. Department of Agriculture
- Terrain from Google (default)
- Topographic map from MyTopo (USA 1:24,000 & Canada 1:50,000)
- Topographic map from USGS via “The National Map” service
- Topographic map from CalTopo.com & USGS (USA 1:24,000) - Best Quality
- Topographic vector maps for Canada
- USA topographic maps from ESRI. Zoom level 12 shows a very nice map for a relatively large area.
- Worldwide topographic maps from ESRI
- Worldwide topographic maps plus crowd-sourced trails from OSM Cycle
- Worldwide street maps from OSM
- Earth with Google earth browser plugin
Topographic Maps Included
Of those maps, the subset of topographic maps most relevant to hikers is described below. I use the map labelled t4 Topo High USA the most because it’s the most up to date for the areas of New Hampshire that I hike in. I can tell this because it does not include trails that were removed from the local trail system, washed out by floods, or closed due to landowner disputes.
- t1 Terrain: This is the same terrain map you see if you use POGM (Plain Old Google Maps). For the USA the contour lines appear to match the contour lines on the 1:24,000 scale USGS topographic maps. For Canada and many other countries the contour interval is 20 meters. Some countries do not have topographic data available.
- t2 MyTopo: These are medium resolution scans (pixels per inch not published) of the 1:24,000 scale USA topographic maps and 1:50,000 scale Canadian topographic maps. This map set also includes the U.S. Forest Service updates including USFS road numbers.
- t3 Topo USGS: These are relatively low resolution scans of the 1:24,000 scale USA topographic maps. These maps are provided by the USGS via a project called “The National Map”. In a few places these maps show old trails that do not appear on the other topographic map sets that Gmap4 displays.
- t4 Topo High: Most of these maps are high resolution scans made at 600 pixels per inch (ppi) of the 1:24,000 scale USA topographic maps. Some maps were scanned at 400 ppi.
- t5 Canada: This is a new type of map that is based on ‘vectors’. If you zoom in you will see that the topographic lines are not smooth curves but instead are a series of short straight lines. These maps are provided by the Canadian government and you can learn more here: http://atlas.nrcan.gc.ca/site/english/maps/topo/index.html
How to Share a Route in Gmap4
Here’s a backpacking route I created for hiking to a remote peak named North Isolation in the White Mountains that’s on the Trailwright’s 72 peaklist. The route runs along the Mt Stanton and Mt Parker Trails instead of the normal Davis Path route. Just click on this hyperlink and the route will be displayed in our browser (the waypoints are encoded in the hyperlink.) You can also create a GPX file within Gmap4 and share it that way.
This is the map (below) you’ll see displayed in your browser when you click on this link. You don’t need to load any software because Gmap4 is a browser-based app. This means that native, device specific apps are not available to use it, but it runs in many different browsers so you should still be able to use it. For example, I can run Gmap4 on an iPad running Chrome as long as I have a live Internet connection.
You also have the option of viewing the route in the other maps provided with Gmap4. For example, try switching to the Aerial Google Hybrid map (as shown below) in the rightmost pull-down menu to see a different map of the route using the same waypoints. This feature is quite helpful if you want to compare a Topo view to an Aerial view with vegetation.
How to Plan a Route and Share it
Here is a quick illustration of the process you’d go through to plan and draw the North Isloation hiking route we shared above.
1. Search for Isolation Mountain
We search for Isolation Mountain and not North Isolation because the latter is rarely marked on maps. North Isolation is located just north of the intersection between the Davis Path and the now-closed Isolation Trail.
2. Draw the Route Waypoints from the Mt Stanton trailhead to the North Isolation summit.
3. Name Waypoints, Route, etc. or Create GPX file
I mainly print the maps I create with Gmap4 so I never bother labelling my waypoints. But it’s probably a good thing to do if you want to publish a route for GPS users.
4. Create Viewable GPX file or download
5. Prepare the map for printing.
I like having gridlines on my map and a current declination so I add them before I print out the route.
Gmap4 is a very powerful online mapping tool that provides excellent quality maps and easy to use hyperlink-based map sharing tools. It’s fantastic for sharing a route with other hikers before a trip because they don’t need any software to view or print it and for planning out off-trail adventures where having a variety of different maps types at your fingertips is very powerful. But for all of it’s strengths, Gmap4 is a little rough around the edges when it comes to usability. Still, if you’re already messing around with GPX files and GPS receivers, you’ve already gotten your hands dirty and may find Gmap4 more inituitive than many other tools available. Personally, I love Gmap4 and I love the fact that it’s free.
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