[GRASS-user] calibrating a interpolated or contour map

[Dylan Beaudette]

On Tuesday 29 July 2008, Tim Michelsen wrote:
> Hello,
> what methodes are recommended to use within GRASS to calibrate a map
> with by using geostatistical methods?
> OK, normally the method depends on the kind of data. Therefore I may
> give an example:
>
> I have long-term meteorological mesurement data (timeseries aggregated
> to monthly frequency) from the climate data logging stations in a
> region. The components are temperature, humidity, wind speed and
> direction as well as precipitation. These are imported by v.in.ascii and
> interpolated into a map. This data may come from a third-party source
> or be obtained by remote sensing.
>
> Since it is difficult to obtain reliable data I put my own three
> stations out in the field at critical points where I have the most
> doubts about the data. I conduct two years of measurements.
>
> How to I update my interpolated map with the new values obtained from
> the three stations?

How about something like this:

# import and interpolate first dataset
v.in.ascii in=large_dataset.csv out=d1 ...
v.surf.rst ...

# looks good / bad
d.rast ...


> Of course, I can just update the corresponding z values of xyz-vector
> (externally in OOo Calc or by scripting) and then interpolate again.
> Or update all values of the input data according to a calculated
> deviation from the longterm value.
>
> But...
> * is there any tool or workflow that could facilitate this?
> * is there any article or report that describes doing such a procedure
> using
> GRASS?

# now compare to my points by patching then re-interpolating:
v.in.ascii in=my_dataset out=d2 ...
v.patch in=d1,d2 out=d3
v.surf.rst in=d3 ...

If you want to compare interpolated values at your locations, without 
re-interpolating try v.what.rast.


>
> I am just asking for ideas and experineces.
> Thanks in advance for any hints or pointers.
>
> I think that this is related to the recent question:
> Thin plate spline for climate point record interpollation?
> http://permalink.gmane.org/gmane.comp.gis.grass.user/24940
>
> Kind regards,
> Timmie

Good luck,

Dylan

>
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-- 
Dylan Beaudette
Soil Resource Laboratory
http://casoilresource.lawr.ucdavis.edu/
University of California at Davis
530.754.7341