[QGIS-trac] Re: [Quantum GIS] #1433: measurements and scale broken in latlon

[Quantum GIS]

#1433: measurements and scale broken in latlon
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        Reporter:  msieczka                                   |         Owner:  timlinux                                      
            Type:  bug                                        |        Status:  new                                           
        Priority:  critical: causes crash or data corruption  |     Milestone:  Version 1.2.0                                 
       Component:  Projection Support                         |       Version:  HEAD                                          
      Resolution:                                             |      Keywords:  scale, projections, measure line, measure area
Platform_version:                                             |      Platform:  All                                           
        Must_fix:  Yes                                        |   Status_info:  0                                             
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Comment (by wonder):

 Replying to [comment:7 cfarmer]:
 > Replying to [comment:6 borysiasty]:
 > > This is an important issue. Many users think the unit selector allows
 some kind of reprojection in the fly and feel confused.
 >
 > I agree, this is an important issue, and once a clear plan of action in
 set in place, likely won't take long to fix...

 I hope so too. I think we should introduce also "unknown" units: by
 default when we don't know layer's CRS or when the OTF projections are
 turned off.

 That also lead me to another idea: does it make sense not to project
 layers which are in different systems? I know it takes some additional
 rendering cost, but having OTF projections turned always on would solve
 several problems at once.

 > As far as I can tell, when using QgsMeasureTool, the QgsDistanceArea
 never has an ellipsoid set... is this correct?

 The logic for measuring is not really good. IIRC currently when the OTF
 projection is turned on it calculates distance/area on a plane, with
 projections turned on it does the calculations on ellipsoid.

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Ticket URL: <https://trac.osgeo.org/qgis/ticket/1433#comment:9>
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