[Proj] geod C library?

[Karney, Charles]

> From: Evan Miller [emmiller at gmail.com]
> Sent: Tuesday, November 30, 2010 10:26
>
> I am looking for the functionality provided by "geod" and "invgeod"
> (great circle calculations) wrapped up in a plain C library. I found
> Charles Karney's Geographic Library, but that's C++.

I'm not sure whether this will help you...  However a C wrapper to
GeographicLib is a possibility.  For example:

interface.cpp:
================================================================
#include "GeographicLib/Geodesic.hpp"

extern "C"
void GeodInverse(double lat1, double lon1, double lat2, double lon2,
                 double *s12, double *azi1, double *azi2) {
    GeographicLib::Geodesic::WGS84.Inverse(lat1, lon1, lat2, lon2,
                                           *s12, *azi1, *azi2);
    return;
}
================================================================

main.c
================================================================
#include <stdio.h>

void GeodInverse(double lat1, double lon1, double lat2, double lon2,
                 double *s12, double *azi1, double *azi2);

int main() {
  double lat1, lon1, lat2, lon2;
  double s12, azi1, azi2;
  scanf("%lf %lf %lf %lf\n", &lat1, &lon1, &lat2, &lon2);
  GeodInverse(lat1, lon1, lat2, lon2, &s12, &azi1, &azi2);
  printf("%.8f %.8f %.3f\n", azi1, azi2, s12);
}
================================================================

Makefile
================================================================
test: main.o interface.o
        g++ -o $@ $^ -lGeographic -Wl,--rpath -Wl,/usr/local/lib
main.o: main.c
        gcc -c $^
interface.o: interface.cpp
        g++ -c $^
================================================================

make test
echo 1 2 3 4 | ./test
45.14416881 45.21398561 313705.445

--
Charles Karney <ckarney at sarnoff.com>
Sarnoff Corporation, Princeton, NJ 08543-5300

Tel: +1 609 734 2312
Fax: +1 609 734 2662



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