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| GeoCommunity Mailing List |
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| Mailing List Archives |
| Subject: | Re: GISList: determining DEM accuracy or error |
| Date: |
03/31/2003 09:35:01 PM |
| From: |
Jayachandran Mani |
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hi
Accuracy is a factor, which indicates the deviation of
of the target file with reference to the source
values. since you have two DEM files, these two DEM
files can be superimposed on to any photogrammetry
image processsing / GIS software which perform DEM
merging. At the end of the operation, it will give you
the various statistical parameters like mean, median,
mode of each DEM, standarard deviation, variance, skew
etc., These statistical parameters can be used as a
guideline for estimating the accuracy of DEM based on
the normal distrribution curve patterns.
Apart from that, the DEM can be superimposed on the
stereo model of the area to check physically how it is
matching with the terrain surface.
Alternatively, for a known location whose height and
XY are known, the height at the same point in the DEM
can be measured and the deviation can be reported as
errors. these are normally called as check point /
control point check against the DEM
In other case, the contours of two different years,
can be superimposed one over the other in autocad or
in any drafting package, to physically check the
deviation of the contour lines and thereafter to check
with the terrain in areas of mismatch to ensure the
validity
Regards
Jay
--- northms@telus.net wrote:
> Hi there,
>
> Can anyone give suggestions about how to report
> accuracy of a DEM and
> measurement derived from a DEM?
>
> I have one DEM each for the same study area in two
> separate years. In each
> case, one-metre contours and additional planimetric
> data were used to build a
> TIN elevation model. The TIN's were converted to
> grid-type DEM's with two-
> metre cell size. The two surfaces were compared by
> subtracting the year1 DEM
> from the year2 DEM.
>
> How do I go about estimating the accuracy (or error)
> of each DEM, and the
> accuracy of difference measurements taken from the
> two DEM's (i.e., year2 -
> year1)? Can anyone suggest methodology or
> references to help with this?
>
>
> thanks,
> sarah
> email. northms@telus.net
>
>
>
>
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