Changeset 14288

Timestamp:

Jul 18, 2007, 8:47:53 AM (19 years ago)

Author:

eugene

Message:

adding ARC projection, fixing STG, adding some comments

File:

• trunk/Ohana/src/libdvo/src/coordops.c (modified) (4 diffs)

trunk/Ohana/src/libdvo/src/coordops.c

@@ -72 +72 @@
       case PROJ_TAN:
       case PROJ_DIS:
+        // R = cot (theta) = cos(theta) / sin(theta)
         if (R == 0) {
           stht = 1.0;
@@ -82 +83 @@
         break;
       case PROJ_STG:
+        // R = (180/pi) [2 cos (theta)  / 1 + sin (theta)]
         stht = (4 - RAD_DEG*R) / (4 + RAD_DEG*R);
         ctht = sqrt (1 - stht*stht);
         break;
       case PROJ_SIN:
+        // R = (180/pi) cos (theta)
         ctht = RAD_DEG * R;
         stht = sqrt (1 - ctht*ctht);
+        break;
+      case PROJ_ARC:
+        // R = 90 - theta (degrees)
+        ctht = sin (RAD_DEG * R);
+        stht = cos (RAD_DEG * R);
         break;
       case PROJ_ZEA:
@@ -161 +169 @@
   double phi, theta;
   double Lo, Mo;
-  double sphi, cphi, stht;
+  double sphi, cphi, stht, ctht;
   double salp, calp, sdel, cdel, sdp, cdp;
   double P, A, Rc;
@@ -201 +209 @@
     cphi = cdel*sdp*calp - sdel*cdp;    /* = cos(theta)*cos(phi) */
 
+    // L = +R sin(phi)
+    // M = -R cos(phi)
+
     switch (proj) {
       case PROJ_TAN:
       case PROJ_DIS:
+        // R = cot (theta) = cos(theta) / sin(theta)
         Rc = hypot(sphi, cphi);
         *L = (stht == 0) ? 180.0 * sphi / Rc :  +DEG_RAD * sphi / stht;
         *M = (stht == 0) ? 180.0 * cphi / Rc :  -DEG_RAD * cphi / stht;
         return (stht > 0);
+      case PROJ_STG:
+        // R = 2 cos(theta) / [1 + sin(theta)]
+        Rc = DEG_RAD * 2 / (1 + stht);
+        *L = +Rc * sphi;
+        *M = -Rc * cphi;
+        return (stht > 0);
       case PROJ_SIN:
+        // R = cos(theta)
         *L = +DEG_RAD * sphi;
         *M = -DEG_RAD * cphi;
         return (stht > 0);
+      case PROJ_ARC:
+        // R = 90 - theta
+        ctht = hypot(sphi, cphi);
+        theta = atan2 (stht, ctht);
+        Rc = 90 - DEG_RAD * theta;
+        *L = (ctht == 0.0) ? 0.0 : +Rc * sphi / ctht ;
+        *M = (ctht == 0.0) ? 0.0 : -Rc * cphi / ctht ;
+        return (TRUE);
       case PROJ_ZEA:
       case PROJ_ZPL:
+        // R = 90 - theta
         Rc = DEG_RAD * M_SQRT2 / sqrt (1 + stht);
         *L =  Rc * sphi;