1 files changed, 15 insertions, 0 deletions
diff --git a/src/3rdparty/proj/adjlon.c b/src/3rdparty/proj/adjlon.c
new file mode 100644
index 00000000..09b3b14b
--- /dev/null
+++ b/src/3rdparty/proj/adjlon.c
@@ -0,0 +1,15 @@
+/* reduce argument to range +/- PI */
+#include <math.h>
+#include <projects.h>
+
+#define SPI     3.14159265359
+#define TWOPI   6.2831853071795864769
+#define ONEPI   3.14159265358979323846
+
+double adjlon (double lon) {
+    if (fabs(lon) <= SPI) return( lon );
+    lon += ONEPI;  /* adjust to 0..2pi rad */
+    lon -= TWOPI * floor(lon / TWOPI); /* remove integral # of 'revolutions'*/
+    lon -= ONEPI;  /* adjust back to -pi..pi rad */
+    return( lon );
+}