1 files changed, 34 insertions, 0 deletions

diff --git a/src/convertcoords.c b/src/convertcoords.c
new file mode 100644
index 0000000..3297d8f
--- /dev/null
+++ b/src/convertcoords.c
@@ -0,0 +1,34 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+int main(int argc, char *argv[])
+{
+        double x = atof(argv[1]);
+        double y = atof(argv[2]);
+
+        double R   = 6365000;
+        double fe  = 5200000;
+        double fn  = 1200000;
+        double ph0 = 0.5235977; // 30deg
+        double ph1 = 0.7853980; // 45deg
+        double ph2 = 0.9599309; // 55deg
+        double l0  = 0.1745329; // 10deg
+
+        double xs = (x-fe)/R;
+        double ys = (y-fn)/R;
+        double ph0_s = 0.25*M_PI+0.5*ph0;
+        double ph1_s = 0.25*M_PI+0.5*ph1;
+        double ph2_s = 0.25*M_PI+0.5*ph2;
+
+        double n  = log(cos(ph1)/cos(ph2))/log(tan(ph2_s)/tan(ph1_s));
+        double F  = cos(ph1)*pow(tan(ph1_s),n)/n;
+        double r0 = F / pow(tan(ph0_s),n);
+        double r  = sqrt(pow(xs,2)+pow(r0-ys,2));
+        double th = atan(xs/(r0-ys));
+
+        double lon = l0+th/n;
+        double lat = 2.0*atan(pow(F/r,1.0/n))-0.5*M_PI;
+
+        printf("%f %f", lat*180.0/M_PI, lon*180.0/M_PI);
+        return 0;
+}