[GRASS-user] r.shaded.relief Output Question

[Rich Shepard]

On Fri, 23 Mar 2012, Daniel Lee wrote:

> I can't imagine that resampling would reverse the DEM values though.

   Me, neither.

> A glance at r.info would give you the answer to that - if the values are
> mostly negative, it should be a pretty good sign that you're either in
> Death Valley or inverted :P

  |   Type of Map:  raster               Number of Categories: 255
  |   Data Type:    DCELL
  |   Rows:         2671
  |   Columns:      3216
  |   Total Cells:  8589936
  |        Projection: Lambert Conformal Conic
  |            N:     735780    S:     655650   Res:    30
  |            E:    2138580    W:    2042100   Res:    30
  |   Range of data:    min = 561.412536621094  max = 2212.32543945312
  |
  |   Data Source:
  |    dem_basin
  |    Source map NS res: 0.999982   EW res: 1.00002702
  |
  |   Data Description:
  |    generated by r.resamp.stats
  |
  |   Comments:
  |    r.resamp.stats input="dem_basin" output="dem10m.avg" method="average"
  |

   Looks normal to me.

> One thing to note with r.shaded.relief though is that it doesn't use the
> GRASS convention for solar azimuths.

   That's what the manual page says.

> ... 235° would be ... from the southwest.

   Yep. That's the way it usually works.

>  When I look at your map (wish the resolution was a bit higher) it looks
> like the sun very well could be coming from that direction (I'm just using
> the rivers as orientation for relative height). Have you tried another
> angle, like taking a look at what the map looks like if the sun's shining
> from 180° (due south)?

   Not yet. I try different altitude angles and moved to 225 degrees so far.

   But, the map appears inverted to me.

Rich