[NUUG kart] ett spørsmål om srtm data filer

[Jon K Hellan]

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.

http://www.viewfinderpanoramas.org/dem3.html#hgt

"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