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Garmin 62s and California Topo: how to avoid too dense contour?

Started by LucaPCP, December 09, 2010, 02:01:13 AM

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Sure, we have access to all the elevation data we want from free government sources. And we have software that can process and display it on the computers. The problem is that we don't know how to turn it into Garmin's format for display on the GPS. That isn't documented anywhere and has resisted efforts to crack so far.

Here's a good start on understanding the concept of .typ files, but it involves hand-coding them with a text editor - see the section starting on page 32:

The online .typ editor is probably the best way to actually create these files, if you're doing anything more than trivial test. The beauty of this approach is that you work directly with the binary files instead of the text files which need to be compiled with cgpsmapper:


If you plan to use a text editor, be sure to use something like Notepad++ (not Notepad).  Notepad++ displays the text well enough to make pattern editing fairly painless.


A few points of clarification:

Shading comes from DEM (Digitial Elevation Model) data not topo lines.  Garmin T Models have DEM data on the GPS and Gamin's 100K Topo Maps will load the DEM data onto you GPS.  If you have DEM data on your GPS, your GPS will show shading on ANY map you have loaded on your GPS.  For example, if you have a T model, your GPS will use the DEM data on your GPS to show shading on any topo map off this site. 

We have not been able to figure out how to make a map that loads the DEM data unto your GPS.

Many people argue don't get the T model and instead get the maps from this site since our topo maps are much better than what the T models have.  However, they forget about the DEM data (which is why I got the 550T instead of the 550).  Besides shading, the DEM data will let you click on any spot in the world and give you the elevation.  It will also add elevation data to a track or route.  For example, if I want to go from St Louis to Denver and create a route-if I go to the elevation screen, it will show me the elevation profile of the part of my route I have not driven yet.


Good point, and I also like to overlay the map with my 400t. The DEM from Garmin's 24k series maps is *much* higher resolution however; I was surprised when I saw it. In a flat coastal area like mine, the 100k DEM looks mostly like sick green, but the 24k DEM shows every little hill and valley.

The Nuvi 3790t actually has DEM in a separate file, gmapdem.img. It looks pretty much the same as the 100k topo DEM to me, and is about a 2GB file covering all of North America. It would be nice if they offered this as a "map" since it would be the perfect companion for third party maps. It adds DEM shading without the overhead of drawing roads and other objects.

I did a couple projects with text editors to create .typ files. It works, but the web editor is a big improvement for this kind of thing. :)


Has anyone figured out what the grid/point spacing of the elevation data is in Garmin's DEM data?
For the 48 States the USGS DEM/NED files at a '10 meter' spacing are nearly 300 Gigabytes.


The OSM wiki has an examination of the data blocks. If I'm understanding this, the spacing is defined here:

Quote0x30     00 d1 8f 00     Distance between pixel (n-s direction)?
0x34    00 05 a2 00    Distance between pixel (w-e direction)?

Remarks: The elevation data is formed from discrete points which are referenced as pixel in the above table.


Quote from: jbensman on December 09, 2010, 09:09:57 AM
So I made him a typ file that told the GPS not to label the contour lines. 

What is the command in the typ file that tells the GPS not to label the contour lines?

Thanks in advance


If you use the online .typ editor (, you would check "extended labels" and choose "no label (invisible)" under Font Style.

This is one of those things that you can do with the online editor but not with the text file based cgpsmapper .typ files. Actually, I never tried it with a contour line, but it works for other lines and points.


OK, thanks!  That's what I was using but when I try to back out the actual text command nothing shows up when I decompile the TYP created with ati TYP compiler.

I guess I'll just have to be satisfied not knowing.


I don't think the text file system used by cgpsmapper has any support for the extended fonts feature. It also doesn't allow you to choose different line rendering modes. These are reasons why you might want to use the online editor instead....

The fact is, both of these systems have been reverse engineered from Garmin's proprietary software (MPC - Mapsource Product Creator). Garmin keeps a tight lid on this - only available to their authorized partners for big $$$.

So there are no standards for creating custom types. The compiled text files are just a cgpsmapper thing.


Quote from: hntr on February 28, 2011, 01:56:15 PM
Quote from: jbensman on December 09, 2010, 09:09:57 AM
So I made him a typ file that told the GPS not to label the contour lines. 

What is the command in the typ file that tells the GPS not to label the contour lines?

Thanks in advance

To only show heights / depths on rollover with a mouse or cursor simply delete the label and add a Height or Depth attribute in the "extras" section for that object in GPSMapedit. EG Depth=20 will show a depth = 20ft on a contour when you hold the cursor over it. No need for the online editor at all. Same thing works with "invisible depths" (0x301 points). There are plenty of other little wrinkles with cgpsmapper too.