[OSGeo-Discuss] 30m SRTM worldwide?

[Sylvain JM Desmoulière]

Hi Carsten,

Continuing your idea I import ASTER QA Plain file ASTGTM_..._num.tiff
in my GRASS location. It show a 1 to 3 stack count which borders areas
superpose with artifacts (see both images end of
http://yepca.org/wp3/?p=303 ).
Next steep is to verify what append if I use the stack number to
correct GDEM using GRASS mapcalc (something like 'if stack layer = 3
than GDEM =+20m'). Then comparing with SRTM-DEM in a untouched forest
area... Let me dream...

Thanks again
Sylvain



2011/8/27 Carsten Troelsgaard <troelsgaard53c at live.dk>:
> Hi Sylvain
>
> The mystery moves to why they didn't 'fix' it in the first place.
> I noted that part of the Amazon Basin has a low overall stack-count.
> The QA file that follows the geoTiff-data is populated with data
> (stack-numbers) in the same format (geoTiff) .. that makes it possible to
> predict troubled areas. I'm not sure if your GIS-tools can incoorporate and
> use the auxillery-data.
>
> Carsten
> --------------------------------------------------------
>
> Sylvain wrote:
>
>> Hi Carsten,
>>
>> It is almost certain that you are right.
>>
>> The chapter "C. Residual Anomalies and Artifacts GDEM" detailed
>> "Artifacts Related to Stack Number Irregular Boundaries."
>> - Decripiton of the "pits" is similar to more or less circular holes I
>> see. The text says they "Regularity and Often Occur with high
>> frequency in Virtually all ASTER GDEM tiles" and "from just a FEW
>> meters to 100 meters or more." Ok
>> - The large positive anomalies similar to "mole run" artifacts (p.23
>> of the text).
>> - Undoubtedly the linear artifact are "step anomaly" (p. 19 text).
>>
>> Thank you for your comments, I'll put them on the blog to let things
>> clear.
>>
>> Bests
>>
>> PS: as you assume, unfortunately, no amazon mystery reveled...
>>
>> Sylvain
>
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