Opened 6 years ago

Closed 6 years ago

#2536 closed defect (fixed)

r.slope.aspect converts to meters

Reported by: annakrat Owned by: grass-dev@…
Priority: critical Milestone: 7.0.0
Component: Projections/Datums Version: svn-trunk
Keywords: r.slope.aspect, units Cc:
CPU: Unspecified Platform: All

Description

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.

Attachments (1)

r.slope.aspect.diff (3.7 KB) - added by annakrat 6 years ago.
r.slope.aspect diff

Download all attachments as: .zip

Change History (3)

Changed 6 years ago by annakrat

Attachment: r.slope.aspect.diff added

r.slope.aspect diff

comment:1 Changed 6 years ago by annakrat

If no objections, I will commit it tomorrow.

comment:2 in reply to:  1 Changed 6 years ago by annakrat

Resolution: fixed
Status: newclosed

Replying to annakrat:

If no objections, I will commit it tomorrow.

Done in r64177 and backported.

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