Zoid99 wrote:
How do i know which ones cover the area i would like to create?
Thanks
Tom
Hi Tom,
On the DEM page link,
ftp://e0srp01u.ecs.nasa.gov/srtm/versio ... 3/Eurasia/, click on the "ParentDirectory" twice to take you up 2 levels, and you will see some documentation on how it all works. It's a .pdf file. Basically, for the SRTM3 data, each file is one degree square. The file name is the lower left corner of that square.
Good luck.
Bill
From the .pdf----
QuickStart
Welcome. If you just can't wait to start playing with the SRTM data, or
just don't have the patience for reading tedious documentation, you'll need
to know at least the following. For more detail see SRTM_Topo.doc.
SRTM data are distributed in two levels: SRTM1 (for the U.S. and its territories
and possessions) with data sampled at one arc-second intervals in latitude and
longitude, and SRTM3 (for the world) sampled at three arc-seconds. Three
arc-second data are generated by three by three averaging of the one
arc-second samples.
Data are divided into one by one degree latitude and longitude tiles in
"geographic" projection, which is to say a raster presentation with equal
intervals of latitude and longitude in no projection at all but easy to manipulate
and mosaic.
File names refer to the latitude and longitude of the lower left corner of
the tile - e.g. N37W105 has its lower left corner at 37 degrees north
latitude and 105 degrees west longitude. To be more exact, these
coordinates refer to the geometric center of the lower left pixel, which in
the case of SRTM3 data will be about 90 meters in extent.
Height files have the extension .HGT and are signed two byte integers. The
bytes are in Motorola "big-endian" order with the most significant byte first,
directly readable by systems such as Sun SPARC, Silicon Graphics and Macintosh.
DEC Alpha and most PCs use Intel ("little-endian") order so some byte-swapping
may be necessary. Heights are in meters referenced to the WGS84/EGM96 geoid.
Data voids are assigned the value -32768.
SRTM3 files contain 1201 lines and 1201 samples. The rows at the north
and south edges as well as the columns at the east and west edges of each
cell overlap and are identical to the edge rows and columns in the adjacent
cell. SRTM1 files contain 3601 lines and 3601 samples, with similar overlap.