Making Transparent Maps for your Garmin GPS with GPX2IMG

I have had a number of questions from readers about how to get some certain trail data onto their GPS. That answer is complicated, because it depends on the trail data and it depends on the GPS you have. If the trail data you want to use is a simple track from someone’s previous ride, you can load it directly onto your GPS. Fitness GPS receivers (like the Edge models with mapping) can do a Virtual Partner based on that file and do performance comparisons and whatnot. With a mapping handheld, you get a basic navigation (it warns you if you deviate from the trail, but not much more). If that .gpx track has more track points than your GPS receiver’s track point limit, you have to reduce the number of points in the track by simplifying it (some programs allow you to do this) or by converting it to a route, which will prompt you to turn (best used on roads where turns occur at intersections, than on trails where turns often occur dependent on terrain).

A better way for navigational reference purposes would be to turn your .gpx files into a Garmin .img file (transparent) that can be overlaid on your basemap (like the topos). This process doesn’t require you to have a fancy new Oregon or eTrex 30. This can be used on one of the original eTrex Legends with a serial cable as well as the new fancy ones. I’m going to use some trail data that was part of a recent Ask the GPSGeek e-mail inquiry, the Coconino Loop. The .gpx files I used can be found by going to that page, or by going directly to their repository at Topofusion.com. This trail is problematic to load as a .gpx file for a couple reasons.

First, the main Coconino Loop file has over 15,000 points, which exceeds the max limit of any GPS I’m aware of (the highest I’ve seen is 10,000 points). Second, there is an alternate route available: the Mingus Bypass, which has over 500 points. This route is technically a network of trails, albeit a simple one (one big loop and a single trail bisecting the main loop to form a second smaller loop). Many urban trail systems are much more complicated networks with dozens of intersections that make the GPX2IMG method even more important. There is also a POI file (waypoints) involved. While the 51 points in this file shouldn’t be a problem for most GPS receivers, you could if you wished

After downloading GPX2IMG, simply load the .gpx files you want. I am using the two trail segments simply because the free version limits you to two .gpx files.  There are ways around this.  You could use Topofusion’s Network utility to merge all intersecting trail segments into a single .gpx.  However, if you’re working with multiple non-intersecting segments you want as a reference on a map, you’ll have to pay up for a license for GPX2IMG.  In this case, it’s not a problem.  In some cases, you may really wish for the waypoints to be basemap POI’s.  In other cases, you’ll want them as .gpx waypoints so you can easily navigate to them and modify them on the GPS.

Go to Preferences in GPX2IMG and name your map in the “Map Name:” field.  I’m calling this one Coconino Loop.  It would be a good idea to change the “Target Directory:” also.  The default is GPX2IMG.  I gave mine the same name as the “Map Name” minus spaces.  Also make sure the “Install Generated Maps in Mapsource” option is checked.  If you don’t have Mapsource, GPSFileDepot has a useful tutorial with the links you need to install it.

If you click the “Track” tab, you can assign names to each GPX file and assign different symbology to each segment within the file.  In this case, each file has one segment.  However, if you were to use Topofusion to merge multiple files into a single Network, you’d have many segments within one file.

Once you have everything how you like, click “Convert (2) Checked Files”.  The free version of the software makes you wait 15sec before you can click okay on the following dialog.  Afterwards, you are given a dialog describing how to find the map you just created in Mapsource.

Open Mapsource and follow the instructions from GPX2IMG to find your map.  It will appear here under the “Map Name” you assigned to it in GPX2IMG.

If you look at the very southern end of the map, you can see the Mingus Bypass we added in GPX2IMG.  You’ll also notice some watermarks.  The “Map Created with http://cgpsmapper.com” mark is there for good.  GPX2IMG uses a shareware version of a DLL file from CGPSmapper, which requires the watermark.  GPX2IMG’s FAQ explains that in more detail.  You can get rid of the “Map Made with GPX2IMG” watermark by paying for the software.  For $20, it’s worth buying this program, and if enough folks buy the software, the other mark might be removed in the future.

If you’re familiar with loading maps onto your GPS from Mapsource, you’ll understand the rest of this process.  If not, you need to be aware that you have to select ALL of the maps you want to load onto your GPS at once.  Use the “Map Tool” (the yellow bordered polygon icon) to select map segments.  Note that with the map you created in GPX2IMG, each .gpx file you’ve inserted into the map has a segment and you’ll need to select each one.  In this case, with 2 .gpx files, there are two segments on the Coconino Loop map I’ve created.  If I also want a topo basemap, I have to switch mapsets and select the tiles I want from that mapset. You’ll see that I’ve added 4 segments from the Arizona Topo mapset, also.  To switch mapsets, simply hit the dropdown, select the new mapset, and then select the tiles you want.

Once you get all your maps selected, you can go ahead and get your GPS plugged in and load the maps.  Once your computer recognizes your GPS, go to the “Transfer” menu and then “Send to Device”.  If you see your GPS in the “Device” field, check “Maps” (if you have other data like maybe the waypoints to send, you will have to load them into Mapsource first), and then click “Send”.  You’ll get a status window that will tell you if the data gets sent successfully.

Disconnect your GPS, and finally you’ll be able to see your maps.  I’ve included a series of screen shots next so you can see exactly the sort of thing you’re dealing with.  You’ll see that the watermarks in the free version of GPX2IMG don’t ruin the usability of the map.  In fact, they look worse when you view the map in Mapsource than you do when viewing the map on your GPS screen.



You can get quite advanced with this method.  This is the quick and dirty way to do it.  You can get it done without watermarks using all free software.  GPSFileDepot has a very in-depth tutorial over that process that just can’t be beat.  That process is extremely flexible so you can put whatever data you like into your map.  If you wish to make your trail maps routable on the GPS (think turn-by-turn directions), you will have to pony up $700USD for the routable version of cGPSmapper.  You might get lucky to find that this has been done for the trails you want.  The My Trails mapset is just one example.  High zoom levels on the AZ Topo map (higher than that displayed in the above screenshots) show an awful lot of trails, also.

2 comments to Making Transparent Maps for your Garmin GPS with GPX2IMG

  • Korey

    Thanks for the great tutorial. I’m getting worn out trying to use just the GPX file for trail maps. I don’t see which tutorial on GPS file depot you’re linking to though.

  • The GPS Geek

    My link takes you straight to it. There are only two steps to it.

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