[GRASS-dev] Sampling STRDS at point location(s)

Blumentrath, Stefan Stefan.Blumentrath at nina.no
Fri Jan 16 01:08:32 PST 2015

Dear all,

On a regularly basis I am asked by colleagues to extract raster based time series data (with > 20k maps) for a (set of) point(s).

After both t.vect.observe.strds, t.sample and t.vect.what.strds seem to have a different purposes,  I do this using a little shell script which mainly uses r.what (please find it attached).

My first question is, did I overlook an existing module which does the job?
The data behind g.gui.tplot would actually be what I was interested in (also for more than just one point)...

I could further-develop the attached shell-script into a new Python-AddOn if that would be of interest, but some improvements in r.what would not make it necessary to have an new module. The main problem is the 400 maps limit in r.what (which is named as a "to do" in the r.what manual). Are there any plans on working on this limitation?

Another nice feature in r.what would be to be able to name an attribute column which is written to the site_name column of the r.what output when coordinates are taken from a vector map (like it is done when coordinates with a site name are used). The latter can be achieved for the "cat" column when "v.to.db"-output is piped to r.what. However it would be nice to be able to use clear text names here as well (which at the moment - as far as I can see - requires to write the coordinates to the attribute table (v.to.db) and then fetch them along with the full-text site name (using v.db.select) in order to pipe them to r.what).

As you can see in the attached script I also transpose the output of r.what because for time series with thousands of maps my colleagues will likely get problems with the number of columns in the software they are using. Therfore a switch in r.what between "horizontal" and "vertical" output (like in v.db.select) would be useful when dealing with thousands of maps in r.what...

Any thought? Would you prefer an enhancement request for r.what or a new addon or none of both?


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