[GRASS-user] Aggregating daily maps in relative strds per month

[Veronica Andreo]

Ciao Nikos, again :)

In case of relative time the temporal unit of the input space time raster
dataset is used. The granularity must be specified with an integer value.

> If the data in fact represent daily data, why don't you register it as
> > absolute time?? In that way, you would just loop over strds...
>
> It is output from r.sun.daily.  Below, looping over monthly Linke
> Turbidity values.
>
> --%<---
> for LINE in `cat monthly_linke_map_start_day_end_day.csv`
> do
>
>     set -- $(echo ${LINE} |tr "|" " ")
>
>     r.sun.daily elevation=srtm4 at PERMANENT aspect_value=0 slope_value=0.0 \
>     albedo=albedo at albedo linke=$1 at linke start_day=$2 end_day=$3 \
>     glob_rad_basename=global_rad_zero insol_time_basename=insol_time \
>     beam_rad_basename=beam_rad_zero diff_rad_basename=diff_rad_zero --o
>
> done
> --->%--
>
> The script creates automatically
> an "relative" strds, and for a good reason I guess.  I can't think which
> of the input's, for r.sun.daily, would fit for an absolute timestamping.
>
> For sure it's not going to be the elevation model.  Linke Turbidity and
> albeo also not.  Any help is highly appreciated if there is something
> for which an absolute timestamping can be justified.
>

Never used this add-on but I see now it creates a strds with relative time.
it seems you cannot change that, yo can't specify anywhere an absolute
time, that's right. But as then you don't have a constant granularity to
aggregate data, cos in fact you want to aggregate it as monthly absolute
data (otherwise you'd just use an integer number, i.e.: 10, 20, 30,
whatever)... I would take maps in the output of r.sun daily and register
them in another strds (with absolute time) and then aggregate monthly...

for STRDS in global_rad_zero beam_rad_zero diff_rad_zero insol_time

t.create type=strds temporaltype=absolute output=${STRDS} title="bla"
description="bla" --o

t.register -i type=rast input=${STRDS} maps=`g.list rast pat=${STRDS}*
sep=,` start="2003-01-01" increment="1 day"
# or whatever pattern you use, or a list of ordered maps

# then the aggregation
t.rast.aggregate input=${STRDS} output=${STRDS}_monthly_average
basename=${STRDS}_average granularity="1 month" method=average

done

just an idea...
or use your script as it was :)

> for STRDS in global_rad_zero beam_rad_zero diff_rad_zero insol_time
> > do
> > t.rast.aggregate input=${STRDS} output=${STRDS}_monthly_average
> > basename=${STRDS}_average granularity="1 month" method=average
> > done
>
> So, the above won't work :-(.  I don't know how bad the idea of having
> preset months (start and end days for such cases) to operate on relative
> s-t data sets.
>

dunno... thing is, in relative time, how do you know for every possible
case at which point does a month start... i mean, for that, you have
absolute time, right? Maybe, r.sun.daily could output an absolute time
strds... don't know if it's feasible though


> Plus, an idea I already expressed elsewhere in the list:  will it be
> useful to have support for multiple LinkeT maps?  Not sure how the
> implementation should look like yet.
>
> > Cheers,
> > Vero
>
> Thanks for caring, Nikos
>

Niente! Not so useful though :)
Cheers,
Vero
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