[GRASS-user] howto make my srtm-dem jump the GIS gap

[William Kyngesburye]

On Aug 9, 2006, at 11:55 AM, Rudolf Maurer wrote:

> Hi there!
>
> I tried Williams
> r.out.gdal in=dem out=dem.tif cre="COMPRESS=PACKBITS" type=Int16
> which looks OK:
> GRASS 6.0.1 (baydem):~ > r.out.gdal in=clean_alle out=clean_test.tif
> cre="COMPRESS=PACKBITS" type=Int16
> Writing format: GTiff
> Writing type:   Int16
> Input file size is 2400, 2400
> 0.Warning 1: Unable to export color table to GeoTIFF file.  Color  
> tables
> can only be written to 1 band Byte or UInt16 GeoTIFF files.
> ..10...20...30...40...50...60...70...80...90...100 - done.
>
> Even though I used d.what.rast to check on the data-format, and I got
> floating point numbers (I guess due to interpolation):
> 10:48:07.5E 47:01:22.5N
> clean_alle in maurerr, quant   (2686)
> clean_alle in maurerr, actual  (2685.749512)
> What's the difference between those two values? What would be the
> common way to get this information?
>
when it's exported to the tiff, the rounded quant number is used.   
The fillnulls step on the SRTM data made this into a float raster.

> TIF is 12MB. My QGIS 0.7.4 "Seamus" does have problems opening it...
> Tomorrow I can check what E$SRI says.
>
>> That is a good point. The 2 Gb limit is still a problem for file- 
>> based data in ArcGIS. Rudolf, is your file around 2 Gb?
>
> Definitely not: ARC-Grids have under 30MB. I use 4 tiles of SRTM-Data,
> 2400 by 2400 cells in 9 arc seconds.
>
> Now Arc-Grid:
> I did
> GRASS 6.0.1 (baydem):~ > r.out.gdal in=clean_alle out=clean_test_arc
> type=Byte format=AAIGrid
> Writing format: AAIGrid
> Writing type:   Byte
> Input file size is 2400, 2400
> 0...10...20...30...40...50...60...70...80...90...100 - done.
>
> File is 26 MB.
> Is type=Byte OK? I would not need big numbers though.

No, that will only give you up to 255 elevation and no negative  
values (for the various below sea level depressions in the world).

-----
William Kyngesburye <kyngchaos at kyngchaos.com>
http://www.kyngchaos.com/

"Oh, look, I seem to have fallen down a deep, dark hole.  Now what  
does that remind me of?  Ah, yes - life."

- Marvin