1 files changed, 28 insertions, 0 deletions
diff --git a/src/cmd/map/libmap/polyconic.c b/src/cmd/map/libmap/polyconic.c
new file mode 100644
index 00000000..a07c97e3
--- /dev/null
+++ b/src/cmd/map/libmap/polyconic.c
@@ -0,0 +1,28 @@
+#include <u.h>
+#include <libc.h>
+#include "map.h"
+
+int
+Xpolyconic(struct place *place, double *x, double *y)
+{
+	double r, alpha;
+	double lat2, lon2;
+	if(fabs(place->nlat.l) > .01) {
+		r = place->nlat.c / place->nlat.s;
+		alpha = place->wlon.l * place->nlat.s;
+		*y = place->nlat.l + r*(1 - cos(alpha));
+		*x = - r*sin(alpha);
+	} else {
+		lon2 = place->wlon.l * place->wlon.l;
+		lat2 = place->nlat.l * place->nlat.l;
+		*y = place->nlat.l * (1+(lon2/2)*(1-(8+lon2)*lat2/12));
+		*x = - place->wlon.l * (1-lat2*(3+lon2)/6);
+	}
+	return(1);
+}
+
+proj
+polyconic(void)
+{
+	return(Xpolyconic);
+}