[GRASS-dev] Unexpected EVI range from "i.vi"

[Moritz Lennert]

On Mon, June 17, 2013 22:58, Nikos Alexandris wrote:
> Markus Metz wrote:
>
>> Feeding the test values and the evi(2) formula to r.mapcalc, the
>> results are more or less in the expected range, still beyond [-1, 1],
>> but not much.
>
> [cut]
>
> Yes, but feeding the "suspect" values in r.mapcalc, still gives,
> correctly,
> large/out of range (regarding EVI's expected range) result(s).
>
> Anyhow, just to have a quick-check on "r.what", should I upload the bands
> in
> question somewhere?  Would anyone have the time to explain/check why
> r.what
> gives different results depending on the extent/resolution for the same
> coordinates?  Which, might be expected, but why does "g.region rows=1
> cols=1"
> set the resolution to... see below:

[...]

>> > g.region -pagc e=784935 n=2695215 rows=1 cols=1 res=30
> -------------------------------------------^------^-----^^
>> >
>> > n=2695230
>> > s=2621340
>> > w=658560
>> > e=784950
>
> ----------vvvvvv
>> > nsres=73890
>> > ewres=126390
> ----------^^^^^^

rows and cols has precedence over res, but res=30 plus -a still has an
effect, so you get an extension that is in multiples of 30, with a
resolution equal to the total extension, since you asked for one row and
one col.

Moritz