[Qgis-user] Area Calculation in Field Calculation

[Jeremy Hill]

Harish,
As my screen capture shows, I am able to select the Layer or Project or Ellipsoid CRS. I am able to do it on a “Line” “Point” and “Polygon” Shapefile (.shp) file. I’m running QGIS 1.8 Lisboa. Maybe check and make sure that you have the most up-to-date version. Apart from that I’m not sure what else to tell you. Hopefully someone else can help.
Jeremy

From: Harish 
Sent: Sunday, July 08, 2012 12:59 AM
To: Jeremy Hill 
Cc: qgis-user at lists.osgeo.org 
Subject: Re: [Qgis-user] Area Calculation in Field Calculation

Thanks! point one is solved but for point two, export/add geometry tool returns the window as attached, there is no option for choosing CRS for area calculation.

Regards


On Fri, Jul 6, 2012 at 10:14 PM, Jeremy Hill <hije14 at gmail.com> wrote:



  ------------------------------

  Message: 4
  Date: Fri, 6 Jul 2012 15:16:09 +0530
  From: Harish <harry.om2000 at gmail.com>
  To: Qgis-user at lists.osgeo.org
  Subject: [Qgis-user] Area calculation in field calculator
  Message-ID:
  <CAKCjEX9Vt_0jvEEiHSMOVGMGRR3wMb-0e6BHiZHmrqnB_4Z_=Q at mail.gmail.com>
  Content-Type: text/plain; charset="iso-8859-1"

  1-
  I converted projection 4326 to 32643(UTM zone 43N) to get are calculation.
  I used geometry operator as $area with creating a new field of decimal
  (real) type with width 10 and 2 precision. I tried with different widths
  and precisions, every time there are 7-8 digits after decimal, like,
  2361773.81506348
  2895003.41503906
  1384160.6237793
  10020411.4874268

  ANSWER1----- You need to uncheck the "Toggle Editing" and "save" your layer and then it will be displayed with the proper width and precision that you set it to.


  2
  Further I read in new functionality list of QGIS1.8 that area/length etc.
  may be calculated by using project (if in metric units) CRS in QGIS 1.8,
  without changing original CRS of layer if it is in Geographic coordinates.
  Is this feature available in 1.8?

  ANSWER2---  It does give you the option that when you use "Export/Add Geometry Column" that it gives you the option to Calculate using Layer CRS, Project CRS, or Ellipsoid. You can save to a new layer or update the current one which your using. I have not experimented with this in different projections to verify the accurate data or the area/length but the "plugin" does work.

  Regards

  OS-Windows7, QGIS 1.8 stand alone

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