[GRASS-dev] [GRASS GIS] #2536: r.slope.aspect converts to meters

GRASS GIS trac at osgeo.org
Thu Jan 8 18:52:56 PST 2015

#2536: r.slope.aspect converts to meters
 Reporter:  annakrat               |       Owner:  grass-dev@…              
     Type:  defect                 |      Status:  new                      
 Priority:  critical               |   Milestone:  7.0.0                    
Component:  Projections/Datums     |     Version:  svn-trunk                
 Keywords:  r.slope.aspect, units  |    Platform:  All                      
      Cpu:  Unspecified            |  
 I am getting here to an old problem when r.slope.aspect converts
 automatically horizontal distance to meters. Details are described in this
 old discussion (only Helena and Glynn involved):


 As a result of this behavior, users with location in feet, have to use
 zscale parameter 0.3048 to get correct result. Most users have their DEMs
 with the same horizontal and vertical units and they would assume no
 vertical scaling is needed, and they end up with incorrect results.

 This behavior is very unintuitive and is source of many errors.

 I attached a diff. I added a warning when running it in location with
 units other than meters and zscale different than one (that's the case I
 was mentioning above). I know some old scripts will start to give wrong
 results, but we can avoid future problems of new users.

Ticket URL: <http://trac.osgeo.org/grass/ticket/2536>
GRASS GIS <http://grass.osgeo.org>

More information about the grass-dev mailing list