[GRASS-dev] r.series: threshold/count method?

Markus Neteler neteler at osgeo.org
Fri Aug 28 16:47:41 EDT 2009


it would be ideal to have a new threshold/count method in r.series.
Example: I am calculating growing degree days (accumulated temperatures
over one year, [1]) and want to know at which day of year (count) this
happens. Input would be 365 growing degree days maps, parameters
a threshold value (e.g. 440 for insect moulting) and the result a
count value per pixel which corresponds to the map number which
I gave as input (which is the day of year DOY in this case).

Would that be hard to implement? A bit of rounding/epsilon will be
involved to match the requested threshold since the input maps
are typically FP maps.

I can imagine more use cases: first frost day in autumn (theshold -0.1°C
or so), input daily minimum temperature maps and more...


[1] http://en.wikipedia.org/wiki/Growing_degree_day

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