[postgis-devel] [PostGIS] #503: ST_Area on small polygons in EPSG:31467 gives incorrect results depending on 32-/64-system-architecture

[PostGIS]

#503: ST_Area on small polygons in EPSG:31467 gives incorrect results depending
on 32-/64-system-architecture
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  Reporter:  mjansen  |       Owner:  pramsey      
      Type:  defect   |      Status:  new          
  Priority:  medium   |   Milestone:  PostGIS 1.5.2
 Component:  postgis  |     Version:  1.5.X        
Resolution:           |    Keywords:               
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Comment (by blaggner):

 Nicklas, I suppose OpenOffice isn't very useful for calculating such
 terms. I used another formula, not based on the cross product of the
 vectors but on the trapezes formed by 2 consecutive points and the x-axis,
 and - depending on if I have eliminated the brackets in my formula or not
 - I get your result in one case and a different result in the other. My
 KCalc (internal calculator from OpenSuse) and PostgreSQL itself are
 getting slightly different results from what OpenOffice gets. And, if I'm
 calculating the area of my triangle-shaped geometries directly in
 PostgreSQL using this formula I found, then I get areas that look very
 reasonable to me (values are corresponding with perimeter). Interesting
 is, if I am using your formula for the direct calculation in PostgreSQL, I
 get again 0.001953125. So, something might be problematic with that
 formula or its calcluation in PostgreSQL, too.

 Should I add examples for my calculation experiments?

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Ticket URL: <http://trac.osgeo.org/postgis/ticket/503#comment:11>
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