#2536: r.slope.aspect converts to meters
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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 |
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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):
http://lists.osgeo.org/pipermail/grass-dev/2004-January/013630.html
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.
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Ticket URL: <http://trac.osgeo.org/grass/ticket/2536>
GRASS GIS <http://grass.osgeo.org>