PROJ4
From MohidWiki
This page explains what is PROJ4 library and how to use it from the command line, in Windows and in Linux.
PROJ4 is an open-source Cartographic Projections library originally written by Gerald Evenden then of the USGS. This library has almost all projection types and it is very usefull to convert coordinates for a series of points.
It is written in C but a Fortran wrapper was developed as part of the GLIMMER project. More information can be found in libfproj4
Contents
Installation
Windows
- Download http://download.osgeo.org/proj/proj446_win32_bin.zip
- Extract and copy "proj" folder to C:\
- Right-click "My Computer" and select "Properties"
- Select "Advanced" tab
- Select "Environment Variables"
- In the "System Variables" box select "Path" and click "Edit".
- At the end of the line, add "C:\proj\bin" and click "OK".
- In the "System Variables" box, click "New".
- "Variable Name" is PROJ_LIB and "Variable Value" is "C:\proj\nad".
- Click OK to close windows.
Now test it:
- Windows/Run/cmd
- cd .. until prompt is C:\>
- write "proj -V" to see the version of the library.
Linux
- Go to your Package Manager or download source code from http://trac.osgeo.org/proj/ and follow the instructions.
Usage
The Proj4 is well documented. Here are some commands that I found useful.
Basic
degrees to meters (forward projection)
proj -f "%.2f" +proj=utm +zone=29 +ellps=WGS84 -7.1 38.2 (input) 666368.11 4229712.04 (output)
meters to degrees (inverse projection)
proj -I -f "%.2f" +proj=utm +zone=29 +ellps=WGS84 666368.11 4229712.04 (input) -7.10 38.20 (output)
Portuguese Military Coordinates (Hayford-Gauss Military System)
- Projection: Gauss-Kruger
- Ellipsoid: Hayford (internacional 1924): a=6378.388Km, b=6356.912 Km
- Datum : Lisbon (Castelo S.Jorge: 38º42’43.631’’N, 9º07’54.862’'W, 111.229m)
- Central Point: 39º40’N, 8º07’54.862’’W
- Origin: -200Km horizontally and -300 Km vertically
proj -f "%.2f" +init=epsg:20790
or
proj -f "%.2f" +init=esri:102164
or
proj -f "%.2f" +proj=tmerc +lat_0=39.66666666666666 +lon_0=-8.131906111111112 +k=1.000000
+x_0=200000 +y_0=300000 +ellps=intl +pm=lisbon +units=m +no_defs no_defs
Universal Transverse Mercator (zone 29N)
proj -f "%.2f" +init=esri:32629
or
proj -f "%.2f" +proj=utm +zone=29 +ellps=WGS84 +datum=WGS84 +units=m
List of projections
List of projections in PROJ4: proj -lp
List of ellipsoids
List of ellipsoids in PROJ4: proj -le
More popular:
- International 1909 (Hayford) intl a=6378388.0m b=6356912m rf=297.
- New International 1967 new_intl a=6378157.5m b=6356772m
- WGS 84 WGS84 a=6378137.0m b=6357002m rf=298.257223563
- Normal Sphere (r=6370997) sphere a=6370997.0m b=6370997m
b = a*(1-f) = a*(1-1/rf)
Portuguese Coordinate Systems in PROJ4
You might want to get the libraries containing the coordinate transformations with Portuguese datum pre-configured here. Install the libs in the proj_lib folder, inside the FWTools folder. By the way, you may want to install FWTools first.
Here's the command line on how to convert from military portuguese to wgs84:
cs2cs +init=pt:dlxhgmil +to +init=pt:etrs89 < coords_input.txt
Internal Links
