[GRASS-dev] area measurements

[Anna Petrášová]

Hi Vincent,


On Sun, Jan 5, 2014 at 10:14 AM, Vincent Bain <bain at toraval.fr> wrote:

> Le dimanche 05 janvier 2014 à 08:42 -0500, Anna Petrášová a écrit :
> >
> > Vincent,
> >
> > On Sun, Jan 5, 2014 at 5:19 AM, Vincent Bain <bain at toraval.fr> wrote:
> >         Hi Anna,
> >
> >         I just tested on r58611. Unfortunately it fails :
> >
> >
> > could you try m.measure separately? Launch it from gui command line or
> > menu so that you have the interactive adding coordinates from map
> > display. Could you post the result of m.measure with and without -g
> > flag?
>
> Yes, here it is with four points describing a 1 km side square :
>
> m.measure
> coordinates=922000,2106000,923000,2106000,923000,2107000,922000,2107000
> units=meters
> Length:  3000.000000 meters
> Area:    1000000.000000 square meters
>
> m.measure -g
> coordinates=922000,2106000,923000,2106000,923000,2107000,922000,2107000
> units=meters
> units=meters,square meters
> length=3000.000000
> area=1000000.000000
>
> I actually didn't want you to use the units parameter, this is why you got
reasonable outputs. Without it you would probably get segmentation fault. I
created a ticket for this:
http://trac.osgeo.org/grass/ticket/2157

Having a closer look at my PROJ_UNITS file, I noticed unit was set to
> "metre" and units was set to "metres". I tried to change these values to
> "meter" and "meters". And now it works just fine.
>

Yes, that makes sense. I was wondering why do you have metres instead of
meters there?


> I can't say when and how one can tweak this variable.
> Do you think this enhancement could be easily backported to 6.4 ?
>

Unfortunately not. One thing is the GUI part which I would have to write
again for grass 6 because although it looks the same, the code of wxGUI is
quite different. And write it for grass 6 would be more difficult. The
other thing is that m.measure is only a grass 7 module so I don't know
which backend should be used for grass 6.

Regards,
Anna


> Yours,
> V.
>
>
>
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