On Apr 10, 2009, at 11:22 PM, <grass-user-request@lists.osgeo.org> wrote:
From: Markus Neteler <neteler@osgeo.org>
Date: April 10, 2009 11:12:40 PM GMT-07:00
To: Tripp Lowe <tripplowe@gmail.com>
Cc: GRASS user list <grass-user@lists.osgeo.org>
Subject: Re: [GRASS-user] NED Shaded Relief, Grass 6.4
Tripp,
On Sat, Apr 11, 2009 at 8:05 AM, Tripp Lowe <tripplowe@gmail.com> wrote:
Hello Folks,
I am trying to create a shaded relief map based on a 30-meter NED file using
r.shaded.relief. The results are very ‘blocky’ (or stair-stepped). Running
a 5-cell average neighborhood across the DEM did not help. Can somebody tell
me the correct procedures I should follow to create the relief map that is
smooth?
I’ve put a screenshot of my initial shaded relief map up here to show you
what I’m talking about…
did you run
g.region rast=your_ned_map -pbefore
r.shaded.relief
? I suspect that your current region is of lower resolution right now.Markus
Additionally, NED data are not very good in this respect. In many (all?) cases, they are DEM’s interpolated from contour maps, which were hand or machine drawn from aerial photo data with surveyed reference points. They tend to have inherent stair steps. So even if you get rid of the blocks, it still probably won’t be the kind of shaded relief that you want. For North America, the 30m SRTM level 3 or 4 data are much better.
Michael