[GRASS-user] cs2cs Command Syntax Check

[Tom Russo]

On Tue, Feb 28, 2012 at 10:05:46AM -0700, we recorded a bogon-computron collision of the <russo at bogodyn.org> flavor, containing:
> On Mon, Feb 27, 2012 at 03:23:55PM -0800, we recorded a bogon-computron collision of the <rshepard at appl-ecosys.com> flavor, containing:
> >    I have many lon-lat coordinates in decimal degree format that are to be
> > converted to spcs Nevada East Zone (FIPS: 2701, ADS: 4601, UTM Zone 11),
> > NAD83, US survey feet or, as the PROJ_INFO in that location has it:
> > 
> > name: Transverse Mercator
> > proj: tmerc
> > datum: nad83
> > ellps: grs80
> > lat_0: 34.75
> > lon_0: -115.5833333333333
> > k: 0.9999
> > x_0: 200000.00001016
> > y_0: 8000000.000010163
> > no_defs: defined
> > 
> >    The command I propose to use is:
> > 
> > cs2cs +proj=latlong +datum=NAD83 +to +proj=utm +zone=11 +datum=NAD83
> > 
> >    Is this correct?
> 
> No.  Nevada East Zone State Plane Coordinate System is not the same as 
> UTM, Zone 11 (even though it may lie in UTM zone 11).   Your command line will 
> return UTM coordinates in meters easting and northing, not SPCS coordinates in 
> US survey feet.
> 
> What you want is to tell cs2cs to use the EPSG number 3421
> as the target coordinate system.   From the PROJ.4 epsg file, that means:
> 
> # NAD83 / Nevada East (ft US)
> <3421> +proj=tmerc +lat_0=34.75 +lon_0=-115.5833333333333 +k=0.9999 +x_0=200000.00001016 +y_0=8000000.000010163 +ellps=GRS80 +datum=NAD83 +units=us-ft +no_defs  <>
> 
> which you can see matches your PROJ_INFO information.
> 
> (On my system, the EPSG database for PROJ.4 is in /usr/local/share/proj/epsg)
> 
> You should use this command line instead:
> 
> cs2cs +proj=latlong +datum=NAD83 +to +init=epsg:3421

For what it's worth, if you are already in a GRASS session in the target
location, you can always use the following command line to get lat/lon
converted to the location's coordinate system:

  cs2cs +proj=latlong +datum=NAD83 +to `g.proj -f -j`

g.proj -j prints out the correct PROJ.4 format coordinate system specification
for the current location.

You'll find that g.proj -j in your location will print out the same data as the 
epsg:3421 entry.  

-- 
Tom Russo    KM5VY   SAR502   DM64ux          http://www.swcp.com/~russo/
Tijeras, NM  QRPL#1592 K2#398  SOC#236        http://kevan.org/brain.cgi?DDTNM
"And, isn't sanity really just a one-trick pony anyway? I mean all you get is
 one trick, rational thinking, but when you're good and crazy, oooh, oooh,
 oooh, the sky is the limit!"  --- The Tick