1 files changed, 29 insertions, 0 deletions
diff --git a/src/cmd/map/libmap/gall.c b/src/cmd/map/libmap/gall.c
new file mode 100644
index 00000000..84da651b
--- /dev/null
+++ b/src/cmd/map/libmap/gall.c
@@ -0,0 +1,29 @@
+#include <u.h>
+#include <libc.h>
+#include "map.h"
+
+static double scale;
+
+static int
+Xgall(struct place *place, double *x, double *y)
+{
+	/* two ways to compute tan(place->nlat.l/2) */
+	if(fabs(place->nlat.s)<.1)
+		*y = sin(place->nlat.l/2)/cos(place->nlat.l/2);
+	else
+		*y = (1-place->nlat.c)/place->nlat.s;
+	*x = -scale*place->wlon.l;
+	return 1;
+}
+
+proj
+gall(double par)
+{
+	double coshalf;
+	if(fabs(par)>80)
+		return 0;
+	par *= RAD;
+	coshalf = cos(par/2);
+	scale = cos(par)/(2*coshalf*coshalf);
+	return Xgall;
+}