dted0 import

[Bernhard Reiter]

Just wanted to import DTED0 elevation data.

It comes in files.
Like: 
-rwxrwxr-x   1 bernhard system      33668 Apr 19  1999 e110_n18.avg
-rwxrwxr-x   1 bernhard system      34162 Apr 19  1999 e110_n18.dt0
-rwxrwxr-x   1 bernhard system      33668 Apr 19  1999 e110_n18.max
-rwxrwxr-x   1 bernhard system      33668 Apr 19  1999 e110_n18.min
-rwxrwxr-x   1 bernhard system      86400 Apr 19  1999 e110_n18.mmm

Okay, e110_n18.dt0 should have the elevation data. The format
shall be similiar to that of dted1.

Never the less, the documentation about importing this seems to be
spare. The  GRASS 4.0 Tutorial: DTED and DEM Elevation Data Extraction,
available from http://www.geog.uni-hannover.de/grass/gdp/welcome.html
(surpisingly under Terrain modeling) only refers to tape data and 
it is not helpful in guiding you which command to use.
	r.in.bin 
or	r.in.ll 
shall somehow work, I guess.

Next question: How to extract information about what is in the file.
(I guess it is in the header) and how to skip that header. :)


Another way might be m.dted.examine and m.dted.extract.
But they both claim in their manpage:

| BUGS
|      The format of the header file for DTED Level 1 and 2 data
|      was changed in 1987.  m.dted.extract and m.dted.examine only
|      operate on DTED data containing pre-1987 headers.

In spite of that you can get some stuff from:
	 m.dted.examine input=china_dem/e110_n10/e110_n18.dt0
| UHL
|  SW LON: 110:00:00E   RES: 30.0 (121 lines)
|     LAT:  18:00:00N   RES: 30.0 (121 points)
|  NE LON: 111:00:00E
|     LAT:  19:00:00N
| UHL
|  SW LON: 110:00:00E   RES: 30.0 (121 lines)
|     LAT:  18:00:00N   RES: 30.0 (121 points)
|  NE LON: 111:00:00E
|     LAT:  19:00:00N
[... and so on, until *EOF* is hit ]

m.dted.extract gets you nowhere, though:


 m.dted.extract input=china_dem/e110_n10/e110_n18.dt0  output=e110_n18dted header=e110_n18header north=19:00:00n
| south=18:00:00n
|  east=111:00:00e west=110:00:00e
| initializing e110_n18dted
|   SW  18:00:00N 110:00:00E
|   NE  19:00:00N 111:00:00E
| m.dted.extract: ERROR: unrecognized tape format - probably not a DMA tape

Run out of time for this evening.
It doesn't seem to be that hard. We should figure it out and update the
documentation. :)

Well I could use gtopo30, I guess.....
	Bernhard
-- 
Research Assistant, Geog Dept UM-Milwaukee, USA.  (www.uwm.edu/~bernhard)
Free Software Projects and Consulting 		         (intevation.net)  
Association for a Free Informational Infrastructure            (ffii.org)
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