[NUUG kart] ett spørsmål om srtm data filer

Jon K Hellan hellan at acm.org
Wed Apr 27 10:00:32 CEST 2011

On 04/27/2011 09:47 AM, Vidar Gundersen wrote:
> 2011/4/27 Håken Hveem <krbjhvee at online.no>:
>> Jeg lurer på om det går an å sammenslå følgende filer til en fil:
>> N60E008.hgt  N60E011.hgt  N61E008.hgt  N61E011.hgt  N62E008.hgt  N62E011.hgt
> er ikke disse egentlig tiff filer? +metadata
> (prøv å bruke montage fra ImageMagick, hacke inn metadata etterpå.)

Tror ikke det.


"HGT File Format

HGT files can be read and converted to other DEM formats by 3dem.

An HGT file covers an area of 1°x1°. Its south western corner can be deduced from its file name: for example,
n51e002.hgt covers the area between N 51° E 2° and N 52° E 3°, and s14w077.hgt covers S 14° W 77° to S 13° W 76°.
The file size depends on the resolution. If this is 1", there are 3601 rows of 3601 cells each; if it is 3",
there are 1201 rows of 1201 cells each. The rows are laid out like text on a page, starting with the northernmost
row, with each row reading from west to east. Each cell has two bytes, and the elevation at that cell is
256*(1st byte) + (2nd byte). It follows that a 3" HGT file has a file length of 2 x 1201 x 1201.

Jon Kåre

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