Other DEM file format ?

[tybern]

Christian,

There a lot of DEM file formats.
So, I think the better (minus work) will be BIL (band interveaved by line).
The HGT format is a BIL format. In HGT, data are in Integer 16, and stand for square tiles 1°x1°, 3061 data per rows.

For the purpose of better accuracy DEM file, I will suggest BIL/HDR/PRJ format (also called ESRI HDR labelled, or ESRI BILL format), :

The .PRJ file is an ASCII file for projection, like that :

Code:

GEOGCS["GCS_WGS_1984",DATUM["D_WGS_1984",SPHEROID["WGS_1984",6378137.0,298.257223563]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]]

This file is mandatory if you want to accept different type of projection. But if you want, for example, only WGS84, it is enough to say "it is WGS84" (HGT files are WGS84, it's conventional).

The .HDR file is an ASCII file for description of the BIL file, like that :

Code:

BYTEORDER      I LAYOUT        BIL NROWS          3601 NCOLS          7201 NBANDS        1 NBITS          32 BANDROWBYTES  28804 TOTALROWBYTES  28804 PIXELTYPE      FLOAT ULXMAP        -4.0000000001111 ULYMAP        48.0000000001111 XDIM          0.000277777777808638 YDIM          0.000277777777839488

In this example, the PRJ and HDR are files after converting an two HGT files into one BIL format.

The .BIL file is like in .HGT. In HGT, pixel  type is INT16, in BIL, it can be other types, FLOAT 32 in this example.

So, I can give you files for testing, but say to me if you prefer any projection (WGS84, or Lambert 93, or...), or only WGS84.
Do you prefer square tiles, or any rectangular size ? Do you prefer Interger16 data or is it possible to use Float type ? (I think float is better for accuracy).

After your reply, I will generate files for you, for testing.

Best regards,

Bernard