[Qgis-user] point pattern analysis in West Africa

[Nicolas Cadieux]

Hi,

It would help to know if you are on QGIS 2x or 3x as things are a bit 
different.  I believe distances in QGIS 2 depends on the project CRS and 
are not ellipsoidal. The distances in QGis 3 are ellipsoidal 
calculations reprojected from the project CRS to the WGS84 ellipsoid.  
Differences you are observing are probably caused by a degree being 
interpreted as a meter or the other way around.

In QGIS 3x make sure all your files are in WGS84 UTM31N and are well 
loaded in that CRS (Change Settings/Options/CRS/CRS for new layers to 
Prompt for CRS).  Right click on the layers in the layers tab and look 
at the CRS in the properties (under information in 3x or General in 2x). 
   Make sure you project is also in WGS84 UTM31N. Make sure the grid you 
are creating in MMQGIS is also in that CRS. (This is to make sure that 
everything is in metre and not in Long/lat.).

In the Measuring tool,  select the correct unit (if you select map units 
and you are in Long/lat, you will have a distance in degrees and not 
meters.  You can also click on "configuration" in the measuring tool to 
configure your preferred distance units (or settings/Options/Map Tools).

If you can't figure it out, I can trouble shoot your files if you send 
them along.


Nicolas


On 2018-09-17 10:27 PM, RMG wrote:
> Hi,
> I have a species localities over four countries in West Africa, mostly 
> straddling Ghana. I have set the layers' CRS to WGS84 UTM31N. I want 
> to do point pattern analysis by overlaying a grid system over the 
> species range. I created a 100 km x 100 km grid layer (MMQGIS), but 
> when I measure each length of the grid using the measurement tool, it 
> shows up as 1 km. What am I doing wrong? If I change the project CRS 
> to Clark 1880, the distance unit correctly shows up, but it measures 
> 180 km. What is the remedy to this problem?
>
> Thanks for your attention.
>
> Reiko M. Goodwin
> facebook.com/GuenonConservationCommunity/ 
> <http://facebook.com/GuenonConservationCommunity/>
>
>
>
>
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