+/** Arc seconds to radians. (arcsec*pi)/(3600*180) = rad */
+#define SG_ARCSEC_TO_RAD 4.84813681109535993589e-06
+
+/** Radians to arc seconds. (rad*3600*180)/pi = arcsec */
+#define SG_RAD_TO_ARCSEC 206264.806247096355156
+
+/** Feet to Meters */
+#define SG_FEET_TO_METER 0.3048
+
+/** Meters to Feet */
+#define SG_METER_TO_FEET 3.28083989501312335958
+
+/** Meters to Nautical Miles. 1 nm = 6076.11549 feet */
+#define SG_METER_TO_NM 0.0005399568034557235
+
+/** Nautical Miles to Meters */
+#define SG_NM_TO_METER 1852.0000
+
+/** Meters to Statute Miles. */
+#define SG_METER_TO_SM 0.0006213699494949496
+
+/** Statute Miles to Meters. */
+#define SG_SM_TO_METER 1609.3412196
+
+/** Radians to Nautical Miles. 1 nm = 1/60 of a degree */
+#define SG_NM_TO_RAD 0.00029088820866572159
+
+/** Nautical Miles to Radians */
+#define SG_RAD_TO_NM 3437.7467707849392526
+
+/** Miles per second to Knots */
+#define SG_MPS_TO_KT 1.9438444924406046432
+
+/** Knots to Miles per second */
+#define SG_KT_TO_MPS 0.5144444444444444444