[gdal-dev] how to judge a file is a DEM file or not?

[Clarke, Trevor]

Also, look at the coverage area, DEMs will often (but not always) have a
nice "round" coverage area such as 30 arcsecond, 3 arcsecond, or 1
arcsecond. The pixel values are often converted to a physical unit such
as feet or meters so you can compare the values to height values in
Google Earth or a similar tool. These heuristics tend to hold for pieces
of larger terrain maps such as SRTM, GTOPO30, ASTER, etc. Small area
terrain maps from stereo imagery, airborne SAR, LIDAR, etc. are less
likely to hold to the coverage area rule but are probably still in
physical units.

-----Original Message-----
From: gdal-dev-bounces at lists.osgeo.org
[mailto:gdal-dev-bounces at lists.osgeo.org] On Behalf Of Even Rouault
Sent: Wednesday, May 02, 2012 3:25 AM
To: weixj
Cc: gdal-dev at lists.osgeo.org
Subject: Re: [gdal-dev] how to judge a file is a DEM file or not?

Selon weixj <weixj2003ld at 163.com>:

> How to judge a file is a DEM file or not?

There's no straightforward answer. Some formats (DTED, SRTM, ...) are
specifically aimed for DEM. But DEM can also be conveyed through more
generic
purpose formats such as GeoTIFF. In that case, looking at the data type
of the
raster bands might give a clue. DEM use generally Int16 or Float32 data
types
(at least, not Byte which has not a sufficient range to express
elevations).
Eventually, looking at the associated metadata might be necessary to
know the
semantics of the data.

Best regards,

Even


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