Examples of maps on Basecamp and a GPS created using Openstreetmap data with newly generated DEM
Plain |
With Contours |
Contours & DEM |
Tibet Using OSM Data |
DEM File structure
Most of the file structure is now understood.:
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Wrong Data |
Correct Data |
With HGT Editor you can
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This .hgt File Contains Void Data |
DEM Pixel Distance Values
The DEM contains the North-South & East-West values for distances between pixels ; the lower the distance, the darker the effect.
Different values can be used for different levels.
Garmin uses the following values for its TOPOs:
Spain , Germany, Austria Holland,Poland Topos |
5520;16560;44176;88368 |
Topo Franc V3 and V4 |
6624 only |
Topo Italy |
2752;8472;44176;88368 |
Sweden |
9936;9936;13248;13248;26512 |
Many have found 9936 to give the most pleasing.effect.
DEM Pixels X & Y
Using &h44 & &h44 |
These are by default set to &h40 ; by tweaking this number you can create some 'interesting' contrasts depending on your zoom level. However, it is clear that Basecamp is struggling to create all tiles and altering the default values is not to be recommended when you create a gmapsupp! Picture shows 2 tiles of the same map. Right : Using default values &h40 and &h40 Left : Using &h44 and &h44 The lower the number the lighter the image. Notice how the top part of the left tile is not rendered. |
DEM Orientation
On a GPS device if you have set orientation to Track up,your DEM is constantly recalculated depending on the direction you are going - this does not apply to your contours!
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