Creating & Loading Terrain Elevation Data

Where do I get the terrain elevation .DEM files from for use with SPTerm?

SoaringPilot uses 30 arc second .DEM formatted data to produce the sub-sampled terrain data. You can use the below image map to download the areas of the world that you wish to use. Instructions for creating the terrain data for SP with these .DEM files can be found in the Readme.pdf file included with software.

They used to originate from ftp://edcftp.cr.usgs.gov/pub/data/gtopo30/global/
or http://www1.gsi.go.jp/geowww/globalmap-gsi/gtopo30/gtopo30.html

Click on the SRTM30 tile to download the Digital Elevation Map (DEM) from the place you select.
All the links will download the data from the USGS site: http://dds.cr.usgs.gov/srtm/version2_1/SRTM30/

World w180n90 w140n90 w100n90 w060n90 w020n90 e020n90 e060n90 e100n90 e140n90 w180n40 w140n40 w100n40 w060n40 w020n40 e020n40 e060n40 e100n40 e140n40 w180s10 w140s10 w100s10 w060s10 w020s10 e020s10 e060s10 e100s10 e140s10 w180s60 w120s60 w060s60 w000s60 e060s60 e120s60

Click in the map above on the area of interrest to download the DEM file for that area. The procedure to convert that DEM file to a SoarPilot terrain database is described in the next section.

When unzipping these files with WinZip (or freeware 7-zip), make sure the size of the DEM file is exactly 57.600.000 bytes (use file properties dialog)

You can also find a similar image map to the above, as well as some very useful utilities for working with and visualizing DEM data at http://www.dgadv.com/srtm30/

The above mentioned NASA site has shut down and DEM data files are no longer available for download by the public. The map is now pointing to the alternate download mentioned above. Please note that the Antartica files are no longer available. I suspect that area is not of much interest for the average soaring pilot anyway ;-)

Procedure to create terrain database using PC

This procedure is for Windows based PC using SPTerm 1.34 or later. SPTerm can be downloaded from the main Soaring Pilot web site.

  • Download and place the DEM file in a sub directory terrain of where the SPTerm.exe program is located.
  • Start SPTerm and select menu command Terrain → Generate
  • The next dialog will pop up:
  • In this dialog enter the upper, lower latitude and left and right longitude of the area you want terrain information generated. The dialog will show in the Aprox. Output Size the estimated size of the resulting terrain database in Kb. In the sample screen shot above the area is from 4 to 12 degrees East and 48 to 55 degrees North (roughly NW of Europe). Make sure to keep the size small enough to fit in Palm memory and still leave room for a log file for a long flight.
  • When you’re satisfied with your inputs, use the Generate button. This will result in a terrain database in PDB format in the terrain directory.
  • Double click this file and Hotsync® to load in your Palm. On next startup of SP this database will be loaded. You can verify this by checking the Show Terrain Box in the Map Settings screen and then switch to the Moving Map screen. An additional box around the area covered by the terrain database will be drawn (you may have to zoom out and pan left/right/up/down to get to see the lines of the box). The Show Terrain Box option is temporary of nature and is not saved, so when you exit SoarPilot the checkbox is cleared on restart.
  • Note: There is a trick for Windows users (depends from your Windows system settings) If it doesn’t work with (dot = . ) try (comma = ,) as decimal separator.

SoaringDotNET also has a feature to generate an airspace database for Soaring Pilot so this can be used as an alternative for SPTerm.


Procedure to create terrain database using MAC OS X

This procedure requires the SPterrainGen.zip file that can be downloaded from the Soaring Pilot Yahoo group site.

  • Download the program to your MAC. Your browser might unarchive the application for you. If it doesn’t, then something like unstuffit should.
  • Double click on the application to launch it.

  • You will see a dialog box that will allow you to enter the dimensions of the area you want to cover. Enter the Latitude of the top and bottom edge and the Longitude of the left and right edges. Top is to the north. The values must be in decimal degrees.
  • Click on the Generate button to create the file. If the program can’t find the needed DEM source files an “Open Files” dialog box will allow you to locate the directory that contains them. The program will remember the DEM file location from then on. You will also be presented with a “Save File” dialog box to allows you to select where and by what name you want the file saved as.
  • If you want to check your work you can check the “Generate test DEM file” checkbox then click Generate. This option will generate two files that can be opened and viewed in a DEM file view such as SimpleDEMViewer. The first will be a DEM file with just the data for the area you selected. The second file is a text file that describes the parameters of the first.
  • Transfer the file to your PALM device.

Some restrictions:

  • The program has only been tested on OS-X version 10.3.x and 10.4.4.
  • It should operate correctly on Intel based Macs but it hasn’t been tested.
  • The program can’t deal with Latitudes below 60 degrees south so no soaring in Antarctica.
  • It probably won’t deal well with regions that cross the 180 degree meridian so no soaring in portions of Alaska.
 
soarpilot/download_terrain_data.txt · Last modified: 2013/11/11 02:51 by amegens
 
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