[GRASS-dev] area measurements

Anna Petrášová kratochanna at gmail.com
Mon Jan 6 17:41:42 PST 2014


Hi Vincent,

just FYI, I fixed (and Markus) the problems with units, so you should now
be able to use 'metres' as well (but in GRASS 7 only).

On Sun, Jan 5, 2014 at 4:05 PM, Anna Petrášová <kratochanna at gmail.com>wrote:

> 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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