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Sinai Challenge

I received an email from PAKO who asked me for detailed instructions on the creation of a map of the Sinai peninsula.  I was on travel when I got his email so I recommended that he take a look at the International DEMS section of this page and that I would send information when I got back home.  By the time I got back, another email was awaiting me with some very nice images of the Sinai.  It seems that the writer was a quick study.  He used the program 3DEM to create several very impressive maps, one of which is shown on the right.

The image was so good that I wanted to see if I could do as well.   I knew that I would need to merge multiple NIMA DTED0 files and the only way I had of doing this was to use the powerful MicroDem utilities.  However, I wanted to use Terragen to make the image, but I did not have any way of importing MicroDem output to .ter format.  So I wrote another conversion utility that I called MDEM2TER in order to convert MicroDem DEMs to Terragen .ter files.  This arrangement worked out so well that I decided to write a short tutorial on the steps you need to take to create this type of international DEM from NIMA data.

The first step is to access the NGA Raster Roam.  When you do you will see a map of the world.  Keep clicking on the map until you zoom in on your area of interest, in this case the Sinai region of Egypt.  Select the menu tab called "Define AOI".  Input the corners of your region of interest using latitude and longitude.  It helps to have a paper map handy to locate the proper coordinates.  Remember that DTED0 quads are approximately 1 degree square.  Because the resolution of this data is so poor, you will need to select an area covered by multiple quads and merge them together.  Nine is a good number.  (I used sixteen NIMA quads for this demonstration.)  Make sure your region forms a rectangle, preferably a square. 

When you have decided on your region, click the "Download Order" tab.  Then click "Download". (Remember, you want to download the DTED0 data, not DOI, CADRG or anything else.)  A second screen will come up.  Click "Build file for download".     When you select this, your profile will be assembled.    When your profile is built, download to a folder on your computer.  Unzip the file.  Multiple DTED files will be created.  Several folders will be created organizing the profile by longitude, for example e031 means 31 degrees east longitude..

Now you are ready to merge the data.  Open MicroDem.  Select "File", "New DEM" and then "Cancel".  When you do this, the "IN-OUT" tab should become active.  Select it.  Select "Merge" "DEMS".  Now select the main DTED folder and go into each longitude folder and select all the files called "xxx.dt0" where "xxx" is something like "n27" (for 27 degrees north latitude).  As you select each .dt0 file a quad will be added to the merge.  Make sure you select all of them (the xxxdt0s, not the others).  When you are done with one folder, go on to the next until all the quads are added to the merge.  When you are done, hit "Cancel" and then save the merge.  You will be asked to close the DEM as soon as it appears on the screen.  This is OK.  Reopen it by selecting "File" and then "New Dem".

Once the DEM is loaded, save it by selecting "File" and "Save DEM"  Once the DEM is saved run MDEM2TER in order to convert the file to a Terragen .ter file.  Use 30 as a scale factor.  Phew.  Now you are ready to open Terragen and render the image.

For my image of the Sinai, I added a canned Terragen surface map called "Desert and Grass"  this surface map comes with Terragen when you download it.  I got rid of all the child surfaces and kept only "Rock".  I adjusted the color of "Rock" to make a desert color buff.  After that, I selected the "Water" tab and set sea level at 65 meters.  This is important because the Sinai, being a peninsula, is surrounded on three sides by water of course.  You will have to play with the sea level number because it will change dependent on the scale factor keyed in when you run MDEM2DEM.

The rest of the composing was pretty routine with the usual viewing location, lighting and other adjustments.  When I was done, I produced the images shown on the right.  One view is northward up the Gulf of Suez from Bur Safajah, the other northward from the Sinai side. They may not be as good as PAKO's but I think they are enough to salvage some pride.

This procedure is one that will work for international DEMS in any region where NIMA data exists.  And until NASA SRTM data becomes available, this is the best most of us will have.

[PAKO's 3DEM Image]

[My Grayscale Merge Image]

[My Terragen Image.  Click to enlarge.]

[Second Terragen Image.  Click to enlarge.]