PROJ.4 How to create custom CRS to displace by x and y?

Question

I'm trying to create a custom CRS with proj4. I need to displace coordinates by adding 10 meters east and 20 meters north from EPSG:32719.

How can I do that with PROJ.4?

Answer 1

The EPSG:32719 is a UTM Zone 19 south setup with:

$ grep  -B1 '<32719>' /usr/share/proj/epsg

# WGS 84 / UTM zone 19S
<32719> +proj=utm +zone=19 +south +datum=WGS84 +units=m +no_defs  <>

which is a shortcut defined in /usr/share/proj/epsg. For the background you can refer to the PROJ.4 description. If you use the full parameter set for the Transverse Mercator projection, you could use x_0 and y_0 to shift the things a little bit more to your needs. With the full parameter set EPSG:32719 is defined as:

+proj=tmerc +ellps=WGS84 +lat_0=0 +lon_0=-69 +k=0.9996 \
+x_0=500000 +y_0=10000000 +units=m +no_defs

and x_0 and y_0 are used to define false easting and ~ northing to prevent negative values in mapping. You could add your offset to +x_0=500010 / +y_0=10000020 ...

To test your setup you could use under LINUX:

$ echo -69 -40 | proj +proj=tmerc +ellps=WGS84 \
 +lat_0=0 +lon_0=-69 +k=0.9996 \
 +x_0=500000 +y_0=10000000 +units=m +no_defs

which gives you:

500000.00   5572242.78

or

$ echo -69 -40 | proj +proj=utm +zone=19 +south\
 +datum=WGS84 +units=m +no_defs 

the same values

500000.00   5572242.78

and

 $ echo -69 -40 | proj +proj=tmerc +ellps=WGS84 \
 +lat_0=0 +lon_0=-69 +k=0.9996 \
 +x_0=500010 +y_0=10000020 +units=m +no_defs

for the shifted coordinates

500010.00   5572262.78

. @ADD Where to get the infos...

Proj.4 uses a very condensed setup form (I like this), but you can get the infos from spatialreference.org in the WKT form

PROJCS["WGS 84 / UTM zone 19S",
      GEOGCS["WGS 84",
          DATUM["WGS_1984",
              SPHEROID["WGS 84",6378137,298.257223563,
                 AUTHORITY["EPSG","7030"]],
                 AUTHORITY["EPSG","6326"]],
              PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],
           UNIT["degree",0.01745329251994328,AUTHORITY["EPSG","9122"]],
           AUTHORITY["EPSG","4326"]],
           UNIT["metre",1,AUTHORITY["EPSG","9001"]],
PROJECTION["Transverse_Mercator"],
    PARAMETER["latitude_of_origin",0],
    PARAMETER["central_meridian",-69],
    PARAMETER["scale_factor",0.9996],
    PARAMETER["false_easting",500000],
    PARAMETER["false_northing",10000000],
    AUTHORITY["EPSG","32719"],
    AXIS["Easting",EAST],AXIS["Northing",NORTH]]

Translation of the parameter to the proj.4 terms in detail:

+ellps=WGS84 is the ellipsoid WGS84 which is also a shortcut
+k_0=0.9996  (alias scale_factor)typical areal correction
              factor for transverse mercator
+lat_0=0     (latitude_of_origin) allways 0 for UTM
+lon_0=-69   (central_meridian) 
+x_0=500000  (false_easting)
+y_0=1000000 (false_northing)

Environment Debian 8, BASH and PROJ.4