Bug report #3244

AddGeometry- faulty units and precision

Added by muscatelle - almost 10 years ago. Updated almost 10 years ago.

Status:Closed
Priority:Low
Assignee:nobody -
Category:Build/Install
Affected QGIS version: Regression?:No
Operating System:Debian Easy fix?:No
Pull Request or Patch supplied: Resolution:invalid
Crashes QGIS or corrupts data: Copied to github as #:13304

Description

Using Tools>GeometryTools>Export/AddGeometryColumns, has some problems with units and precision.

Output seems to be in units of 100km eg

An area 69.38Ha (measured using the measurement tool) is output as 6.9e-05
Perimeter ~ 3.3Km (measured using the measurement tool) is output as .032753

This has the potential to cause errors and produce misleading information on subsequent calculations

Project units are m.

Sample files before and after Add Geometry are attached

Workaround is at: http://forum.qgis.org/viewtopic.php?f=2&t=7531#p15730

saCensus2006_test.zip - Before and after AddGeometry operation (70.5 KB) muscatelle -, 2010-11-23 03:26 AM

History

#1 Updated by cfarmer - almost 10 years ago

  • Resolution set to invalid
  • Status changed from Open to Closed

The attached shapefile is not in a projected coordinate system, so measuring area and perimeter does not really make sense. As mentioned in the forum thread linked to this ticket, you will need to reproject your data to a projected coordinate system that supports measuring areas. This tool does not use the project CRS, and for good reason: it outputs the area and perimeter as attributes of a layer, so while the project properties may vary from project to project, the layer itself does not.

I am going to close this as 'invalid'. If you feel that this should not be the case, please feel free to reopen the ticket.

Carson

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