[Mapguide-trac] [mapguide-trac] #2891: Measure Distance is Incorrect When using PseudoMercator ESPG 3857

[MapGuide Open Source]

#2891: Measure Distance is Incorrect When using PseudoMercator ESPG 3857
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   Reporter:  crispinatime    |      Owner:  (none)
       Type:  defect          |     Status:  new
   Priority:  medium          |  Milestone:  4.0.1
  Component:  Viewer Command  |    Version:  3.0.0
   Severity:  major           |   Keywords:
External ID:                  |
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 When using the MapGuide built-in Measure Distance on maps using
 PseudoMercator ESPG 3857 the distance is incorrect.

 It is assumed that Measure Distance function uses the projected
 coordinates to calculate distance using Pythagoras.  This is fine for most
 local projections where the projection is designed to create a
 representative Cartesian coordinate system for the geographic area.

 However, for PseudoMercator where the Eastings have larger px/M at higher
 latitudes this results in measure distance being significantly out.

 Options would be for all cases to re-project coordinates to la/lon and use
 great circle or geodesic distance.
 Or for 3857 to apply a cosine (or is it sine) latitude correction to the
 eastings value before Pythagoras distance is calculated.
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Ticket URL: <https://trac.osgeo.org/mapguide/ticket/2891>
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