Re: [Qgis-user] Query re: Area measures

[Mike Shand]

Hi Hugh,

I did some work recently on the Tanzania 2012 Census District file from 
downloaded from the NBS website plus the census data.
I converted the Arc60 lat/long file to a projected WGS 84 UTM zone 36S 
file in QGIS, calculated the Geometry in sqkms then exported the file to 
WGS84 lat/long.  This seemed to work fine as I was then able to 
calculate the population density.


Any problems I can send it offline.

Mike

Mike Shand,
FRSGS; MAppSci; FBCartS,
Honorary Research Fellow
(GIS Cartography)
Geographical & Earth Sciences,
University of Glasgow,
Scotland, U.K.
Tel: +44 (0)141 330 4780
E-mail: mike.sh...@glasgow.ac.uk 
Hon. Secretary:  Society of Cartographers http://www.soc.org.uk/
HOME PAGE & TANZANIA Links: 
http://www.gla.ac.uk/schools/ges/staff/mikeshand/ 




The University of Glasgow, charity number SC004401


On 13/09/2013 17:13, Wenban-Smith wrote:
My QGIS project uses a .shp file of 179 districts in Tanzania. I wish 
to know the area of each district in sq km but the Geometry-$area 
function (in the field calculator of the Attributes table) only 
reports areas in decimal degrees (whereas the individual area 
measuring tool from the toolbar reports sq km but is tedious to use 
and not precise). It appears looking under Settings/Project Properties 
[General tab] that it is possible to convert to meters only when CRS 
transformation is disabled but there is no guidance how to do this 
(nor why this should be necessary). I have tried converting the CRS 
from Arc 1960 to one the UTM ones but this did not help.

Grateful for any advice more experienced users can offer.
Hugh W-S


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Re: [Qgis-user] Query re: Area measures

[Andre Joost]

Am 13.09.2013 18:13, schrieb Wenban-Smith:

I have tried
converting the CRS from Arc 1960 to one the UTM ones but this did not
help.



You have probably used 'Set CRS for layer', but this is not a real 
conversion. Change it back to Arc 1960, and try 'Save As ...' and select 
the UTM CRS for the new file, and add that file to the canvas.


HTH,
André Joost


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Re: [Qgis-user] Query re: Area measures

[Lene Fischer]

Hi Hugh,
You have to mark the layer>Save As
Choose an UTM projection so you can calculate in m2 and km2.
Close the original layer and zoom to the new UTM layer - This only for 
visualizing - not for any function..

Click on Attribute table>Fieldcalculator
Either make a new field or update an exsisting field.

I´ve made a small video to show how to. - Sorry I´m using in danish version ;-)
http://screencast.com/t/ZQJyb6zj

Regards
Lene Fischer

Fra: qgis-user-boun...@lists.osgeo.org [qgis-user-boun...@lists.osgeo.org] på 
vegne af Wenban-Smith [wen...@globalnet.co.uk]
Sendt: 13. september 2013 18:13
Til: qgis-user@lists.osgeo.org
Emne: [Qgis-user] Query re: Area measures

My QGIS project uses a .shp file of 179 districts in Tanzania. I wish to know 
the area of each district in sq km but the Geometry-$area function (in the 
field calculator of the Attributes table) only reports areas in decimal degrees 
(whereas the individual area measuring tool from the toolbar reports sq km but 
is tedious to use and not precise). It appears looking under Settings/Project 
Properties [General tab] that it is possible to convert to meters only when CRS 
transformation is disabled but there is no guidance how to do this (nor why 
this should be necessary). I have tried converting the CRS from Arc 1960 to one 
the UTM ones but this did not help.

Grateful for any advice more experienced users can offer.

Hugh W-S

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[Qgis-user] Query re: Area measures

[Wenban-Smith]

My QGIS project uses a .shp file of 179 districts in Tanzania. I wish to know 
the area of each district in sq km but the Geometry-$area function (in the 
field calculator of the Attributes table) only reports areas in decimal degrees 
(whereas the individual area measuring tool from the toolbar reports sq km but 
is tedious to use and not precise). It appears looking under Settings/Project 
Properties [General tab] that it is possible to convert to meters only when CRS 
transformation is disabled but there is no guidance how to do this (nor why 
this should be necessary). I have tried converting the CRS from Arc 1960 to one 
the UTM ones but this did not help.

Grateful for any advice more experienced users can offer.

Hugh W-S___
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