Compiling the ASTER GDEM, what I've learnt

Here is what I've learnt during the three steps required to compile the ASTER GDEM into a topographic map viewable on a Garmin GPSr.

Vectorisation

I used dem2topo running on an IDL Virtual Machine running on Linux with the following settings:

SF 5
Minor 10m
Intermediate 100m
Major 500m
Shoreline 2m

The great thing about dem2topo is that it can run in batch mode - unattended. Just get the settings right and let it go - for a few days.

Oddly, I can't figure out what the shoreline setting actually does.

The above settings are pretty standard, I'd thing. I've used the same settings since compiling SRTM v2 two-years ago.

Converting a Polish MP to a Garmin IMG

This is the most tedious part. Here are some tips:

Firstly, use the latest version of cgpsmapper. I used version 0.98e as it can cope with significantly larger maps.

Secondly, use a good text editor which can cope with large files (instead of using GPSMapEdit) to copy and paste on a new MP file header . I used the following:

[IMG ID]
ID=60071100
Name=maps.three15.org ASTER-GDEM1
Elevation=M
Preprocess=N
TreSize=1000
RgnLimit=1024
POIIndex=N
Copyright=Data sources http://asterweb.jpl.nasa.gov/|Compilation http://maps.three15.org/
Levels=4
Level0=24
Level1=21
Level2=19
Level3=17
Zoom0=0
Zoom1=1
Zoom2=2
Zoom3=3
DrawPriority=26
Transparent=Y
SimplifyLevel=10
[END-IMG ID]

Note: You'll need to change the ID for each file - it needs to be unique. I generally used a TreSize of 1000 although for the largest map, I had to use a smaller value (800) or else it would generate errors during compilation. The SimplifyLevel of 10 uses the least simplification. Level0 should be 24 for maximum detail.

It is best to create a batch file to compile all the maps in sequence so you don't need to attend to the computer.

Creating a Preview file for Mapsource

Can generally follow the instructions provided with cgpsmapper. I deleted all the contour lines on the overview file because it remained superimposed even when the map was zoomed in.

Would have liked to be able to make the maps compatible with newer versions of Mapsource. Any ideas?

Hello From newbie

Hi Weiaun,
I truly admired of your work here. Creating something big for free is something not many people do. Keep up the good job. I am going to install your topo into my GPSMAP 60csx.