Proj4

Coordinate system conversions are needed for several SCEC projects.

Example Conversions

Converting WGS84 to UTM Zone 11 using cs2cs

• cs2cs -v +proj=latlong +datum=WGS84 +to +proj=utm +zone=11 +datum=WGS84

-bash-4.2$ cs2cs -v +proj=latlong +datum=WGS84 +to +proj=utm +zone=11 +datum=WGS84
# ---- From Coordinate System ----
#Lat/long (Geodetic alias)
#	
# +proj=latlong +datum=WGS84 +ellps=WGS84 +towgs84=0,0,0
# ---- To Coordinate System ----
#Universal Transverse Mercator (UTM)
#	Cyl, Sph
#	zone= south
# +proj=utm +zone=11 +datum=WGS84 +ellps=WGS84 +towgs84=0,0,0
-118.00 34.00
407650.40	3762606.66 0.00

Online Implementation

• CS2CS Online

Example Python Code

-bash-4.2$ more test_pyproj.py
#!/usr/bin/env python
#
# Name: test_pyproj
# Usage:
#  Simple example showing how to use pyproj to convert from lat/lon to UTM zone 11
#
import pyproj

#define a projection with Proj4 Notation
latlon_string="+proj=latlong +datum=WGS84 +ellps=WGS84"
utm_string="+proj=utm +zone=11 +datum=WGS84 +ellps=WGS84"

latlon= pyproj.Proj(latlon_string)
utm_s= pyproj.Proj(utm_string)

vals=[-118.0,34.0]
x,y= pyproj.transform(latlon,utm_s,vals[0],vals[1])
print "UTM E: ", x
print "UTM N: ", y

Example C Code and Makefile

#include <proj_api.h>

main(int argc, char **argv) {
     projPJ pj_merc, pj_latlong;
     double x, y;
     int p;

     if (!(pj_merc = pj_init_plus("+proj=merc +ellps=clrk66 +lat_ts=33")) )
        exit(1);
     if (!(pj_latlong = pj_init_plus("+proj=latlong +ellps=clrk66")) )
        exit(1);
     while (scanf("%lf %lf", &x, &y) == 2) {
        x *= DEG_TO_RAD;
        y *= DEG_TO_RAD;
        p = pj_transform(pj_latlong, pj_merc, 1, 1, &x, &y, NULL );
        printf("%.2f\t%.2f\n", x, y);
     }
     exit(0);
}

test_proj4.o: test_proj4.c
	gcc -o test_proj4 -lproj -L/home/scec-00/maechlin/workspace/proj4/lib -I/home/scec-00/maechlin/workspace/proj4/include test_
proj4.c

FAQ

• Online FAQ
• what is the third return parameter in UTM values
  • input lat/long can include elevation. Third returned UTM param is elevation. When no lat/lon elevation used, utm return elev is 0.0
• What is the +no_defs parameters?
  • "The "no_defs" item ensures that no defaults are read from the defaults files. Sometimes they cause suprising problems." http://lists.osgeo.org/pipermail/mapserver-users/2003-November/046863.html

Building Proj4

• Proj4 built on Centos using the ./configure make, make install. Since we are building on a shared cluster, we needed to ./configure --prefix=/user/scec-00/maechlin/workspace/proj4 (installation path to local directory)
• Installation of proj4 on Mac (high sierra) failed.
• Installation of current proj4 on USC HPC succeeded.
• Didn't try installing pyproj on Mac. It can use either installed proj4, or try to build its own
• Used conda install pyproj on Anaconda 2 instance on USC HPC

Online Documentation

• Proj4 and GMT
• UCVM-P Example Strings
• Proj4 wikibooks
• Defines return paramater elevation
• Python Examples
• More Python Examples
• C example
• More C Examples

Downloads and Documentation

• Proj4 Download - Proj4 4.9.3
• Prog4 Website

• PyProj Download - pyproj 1.9.5.1
• PyProj Documentation]

Related Entries

• High-F
• UCVM