[GRASS-user] Correctly Converting LL to LCC

[Rich Shepard]

On Tue, 29 Dec 2009, Glynn Clements wrote:

> Do you end up with feet? Or do you end up with metres but you're comparing
> against a reference given in feet? Your previous comment suggests the
> latter:

Glynn, et al.:

   I think that this time I have it right.

   Created a new location with the projection information based on a .prj
file (for the hydrologic basins) and imported that map. When I look at
PROJ_UNITS I see they are in feet:

unit: Foot
units: Feet
meters: 0.3048

   This leaves me with a question about the PROJ_INFO contents:

name: Lambert Conformal Conic
proj: lcc
datum: nad83
ellps: grs80
lat_1: 43
lat_2: 45.5
lat_0: 41.75
lon_0: -120.5
x_0: 399999.9999999999
y_0: 0
no_defs: defined
nadgrids: WO

   The x_0 value seems to be in meters (in earlier locations it was rounded
up to 400000) rather than feet. Will this cause me problems if I continue to
re-import into the new location and integrate all maps?

   After running 'g.region vect=basins' and 'g.region -p' I see:

projection: 99 (Lambert Conformal Conic)
zone:       0
datum:      nad83
ellipsoid:  grs80
north:      1683494.51666667
south:      4017.2
west:       222006.05
east:       2367279.85
nsres:      1.00000019
ewres:      0.99999991
rows:       1679477
cols:       2145274
cells:      3602938341698

   The rows, cols, and cells seem extra large. This is a vector map so it
probably doesn't matter, but I'll be re-importing the DEM where it will
matter. Should I also clean up the resolution so both values are exactly
1.0?

Thanks,

Rich