Bug report #1687

Measure tool is very wrong

Added by kwilliams4 - over 10 years ago. Updated over 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:fixed
Crashes QGIS or corrupts data: Copied to github as #:11747

Description

I have a shapefile that has a projection of World Mercator (EPSG:54004).

My view is set with the same coordinate system. My measurement units are set at meters. (Both of which should hopefully be set automatically, but neither are when adding the data to a new map.)

When I measure across the width of the continent of the united states, I get a distance of about 1.8 kilometers! That is obviously incredibly wrong! As currently implemented, the measure tool is completely useless. This isn't just a metric versus imperial issue. It's 100% completely off. For QGIS to be considered even a decent viewer for GIS data the measure tool at least ought to work as it says it should.

I'm using Ubuntu 9.04 with QGIS 1.0.1 installed from the proper repository.

Screenshot.png - Screen capture showing the error (140 KB) kwilliams4 -, 2009-05-12 12:31 PM

History

#1 Updated by Alex Mandel over 10 years ago

Please double check that your layer projection definition is correctly.
Using EPSG: 3395 which is an identical proj string (as far as I can see) to 54004 it works fine.

The coordinates in your screenshot do not correspond to the correct location of any part of the US in the projection you specified.

#2 Updated by kwilliams4 - over 10 years ago

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

It appears that the Ubuntu repository ogr2ogr was not projecting the data properly (didn't read the source projection correctly) ruining the coordinates and not transforming the geometry.

After discovering the projection problem, the measurement does indeed work properly, although I wish it compensated distance measurements for latitude like uDig does with this projection. As-is, the measure tool now gives identical results to ArcMap - no corrections applied on projected coordinate systems.

Thanks for the quick response. I guess I should've noticed that bad projection immediately in hindsight.

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