[Qgis-user] Wrong area with OTF activated

[Carlos Cerdán]

Hi Gino

Thank you for your interest. I was working in CRS WGS 84 / UTM 17s (EPSG =
32717) and destination was same. I also had some layers in lat/long CRS
(EPSG 4326), moreover, in QGIS settings ---> CRS options, it was activated
"Habilitar la reproyección al vuelo si las capas tienen un CRS diferente"
(Activate on the fly reprojection if layers have different CRS?), so it was
activated automatically even if I deactivate this option for the project...
and QGIS calculates wrong area for my UTM polygons.

Then, I suggest that when we have to calculate areas or another geometry
value, it's safe to deactivate OTF crs for QGIS, from menu Configuration
--> Options --> SRC, before doing the work.

Best wishes

Carlos



2014-07-04 2:06 GMT-05:00 Gino Pirelli <luipir at gmail.com>:

> what is your destination (OTF) crs?
>
>
> On 3 July 2014 17:37, Carlos Cerdán <sig.upagu at gmail.com> wrote:
>
>> Dear QGIS users
>>
>> I was preparing a question about calculating areas because I had an
>> issue: calculated area in QGIS was different (and wrong) that ArcGIS (right
>> value) ... but i found the answer. It can be useful for your work (as it
>> was for mine) so here is a comment:
>>
>> I was working in UTM src (SRC = 32717, in notification, down right
>> corner), but with "on the fly SRC transformation" activated. When I use
>> field calculator, the value of area is greater (and wrong) than when it's
>> calculated with "on the fly.." deactivated (right area value).
>>
>> So, in QGIS, the right way to make geometry calculus is matching SRC of
>> your project and your layers and working deactivating "on the fly..."
>>
>> Greetings
>>
>> Carlos
>>
>>
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>>
>
>
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