[GRASSLIST:5710] Re: v.proj problems - state plane to UTM

[Eric G. Miller]

On Sun, Mar 02, 2003 at 12:13:23PM -0500, Philipp Molzer wrote:
> Hi,
> I'm using grass5.0.0 on Linux RedHat8 (intel).
> I have a DEM upon which I'd like to overlay some census data (vectors). 
> The DEM is in UTM format while the vectors are in state plane format. 
> Both locations are NAD83.  Both cover the area of Essex County, New 
> Jersey, USA. When I use v.proj to bring the vectors from my state plane 
> location to my UTM location, the resulting vector data has coordinates 
> that seem to be incompatible with the DEM coordinates.  The east and 
> west bounds of the imported vector layer appear to be way off.

> Source of vectors
> 
> Vectors were imported into a location with these specifications:
> 
>    name:    State Plane
>    datum:   nad83
>    dx:      0.000000
>    dy:      0.000000
>    dz:      0.000000
>    proj:    tmerc
>    a:       0.63782064e+07
>    es:      0.6768657997291094e-02
>    x_0:     0.6096012192024384e+06
>    y_0:     0
>    k:       0.999975e+00
>    lon_0:   74d40'w
>    lat_0:   38d50'n
>    -----------------------------------------------------------
>    PROJ_UNITS file:
>    unit:    foot
>    units:   feet
>    meters:  0.3048000000

I believe the above projection info is incorrect for New Jersey 
State Plane of 1983 (it appears to be the spec for 1927, with the
wrong datum name).  The biggest difference, will probably be that
the 1983 coordinates are probably measured in meters.  I have the
following projection spec., sans units (since states didn't necessarily
follow the 1983->meters recommendation).

# 2900:State_Plane_1983_New_Jersey                                                   
name: State_Plane_1983_New_Jersey                                                    
datum: nad83                                                                         
ellps: grs80                                                                         
y_0: 0                                                                               
es: 0.0066943800229                                                                  
a: 6378137                                                                           
dx: 0                                                                                
dy: 0                                                                                
dz: 0                                                                                
lat_0: 38.8333333333333                                                              
f: 298.257222101                                                                     
proj: tmerc                                                                          
lon_0: -74.5                                                                         
k: 0.9999                                                                            
x_0: 150000 

Replace the mapset/PERMANENT/PROJ_INFO file with the above info, and
replace the PROJ_UNITS file with:

unit: meter
units: meters
meters: 1.0

HTH,
-- 
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