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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



  • Download
  • 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.



The Proj4 is well documented. Here are some commands that I found useful.


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


proj -f "%.2f" +init=esri:102164


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


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

External Links