Adding and modify many useful function

in their header file:
-blh2enu.h
-xyz2blh.h
-rahcal.h
-deg2dms.h
-degRrad.h

degRrad.h

@@ -0,0 +1,27 @@
+#ifndef _DEGRRAD_H_
+#define _DEGRRAD_H_
+#define PI 3.141592653589793
+
+/* -------------------------------------------------------------------------- */
+/// @brief 角度转弧度
+/// @param deg 
+/// @return 返回弧度
+/* -------------------------------------------------------------------------- */
+double deg2rad(double deg)
+{
+    double rad = (PI / 180) * deg;
+    return rad;
+}
+
+/* -------------------------------------------------------------------------- */
+/// @brief 弧度转角度                       
+/// @param rad 
+/// @return 返回角度
+/* -------------------------------------------------------------------------- */
+double rad2deg(double rad)
+{
+    double deg = (180 / PI) * rad;
+    return deg;
+}
+
+#endif