[GRASS-user] r.proj: fixing a failure

[Rich Shepard]

On Tue, 22 Dec 2009, Daniel Victoria wrote:

> So, in order to know where you projected raster will fall, you can use
> the v.in.region trick. The command will create a bounding box in your
> map and you can project the vector (using v.proj), and not wory about
> the current region. Then you set your region to the recently projected
> vector (g.region vect=box) and fix your resolution. Now you are ready
> to project your raster and you know the current region matches the
> region where your raster is coming from.

Daniel,

   Despite my reading the r.proj man page I missed the critical point that
you and Hamish tried pointing out: that v.in.region is run on the raster
location, not the target location.

   Working my way through the r.proj man page note (as you summarize above),
I end with screwy region results.

   v.in.region worked; I call the output area (it should be area and not
line, correct?) 'dembox.' Exiting grass and restarting to reset the location
to that of the project, I ran 'v.proj input=dembox
location=dem10m_northwest' without error. However, running 'g.region
vect=dembox' followed by 'g.region -p' shows:

projection: 99 (Lambert Conformal Conic)
zone:       0
datum:      nad83
ellipsoid:  grs80
north:      1735231.4372465
south:      1120657.13248051
west:       -768668.81031769
east:       40643.22944943
nsres:      32.8315778
ewres:      32.83479551
rows:       18719
cols:       24648
cells:      461385912

   Before running 'g.region vect=dembox' 'g.region -p' showed:

proj:       99
zone:       0
north:      1326000
south:      1278000
east:       817000
west:       766500
cols:       1538
rows:       1462
e-w resol:  32.83485046
n-s resol:  32.83173735
top:        1
bottom:     0
cols3:      50500
rows3:      48000
depths:     1
e-w resol3: 1
n-s resol3: 1
t-b resol:  1

   Both north and south were extended, but the east-west bounds seem totally
unrealistic.

   What might I have missed here? To what should I change the e-w and n-s
resolutions after fixing the first issue?

Thanks,

Rich