[GRASSLIST:7844] Re: visualize DEM error

[Dylan Beaudette]

Couple ways that are outlined in this book [1] suggest making 
histograms of elevation and aspect data. if you see spikes at regular 
intervals in either graph then you have some artifacts - possibly due 
to the use of contours as your input data. You can do this with the 
GRASS-R interface in a couple of minutes.

Another quick check, does your DEM support realistic flow patterns, 
when modeled with something like r.terraflow? i.e. do numerous sinks 
and dams cause water to move with no outlet, when expert knowledge of 
the area suggests otherwise? Comparison with an alternate source of 
stream data may also shed some light on the quality of the DEM.

How did you create the DEM, and from what type of source ?

[1]	J. P. Wilson and J. C. Gallant, editors. Terrain Analysis. John 
Wiley and Sons Inc., New York, 2000.


--
Dylan Beaudette
Soils and Biogeochemistry Graduate Group
University of California at Davis
530.754.7341


On Aug 10, 2005, at 12:46 AM, orkun wrote:

> hello
>
> how  can  I visualize DEM error ?
> how can I interpret whether DEM which I have created is correct ?
>
>
> could you give me hints ?
>
> regards
>
> Ahmet Temiz
>
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