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 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.