[GRASS-CVS] hamish: grass6/raster/r.coin prnt_entry.c,2.0,2.0.6.1

[grass at intevation.de]

Author: hamish

Update of /grassrepository/grass6/raster/r.coin
In directory doto:/tmp/cvs-serv1020/grass6/raster/r.coin

Modified Files:
      Tag: releasebranch_6_2
	prnt_entry.c 
Log Message:
more precise conversions to square miles and acres
  (merge from HEAD)


Index: prnt_entry.c
===================================================================
RCS file: /grassrepository/grass6/raster/r.coin/prnt_entry.c,v
retrieving revision 2.0
retrieving revision 2.0.6.1
diff -u -d -r2.0 -r2.0.6.1
--- prnt_entry.c	9 Nov 2004 14:13:55 -0000	2.0
+++ prnt_entry.c	16 Nov 2007 11:15:15 -0000	2.0.6.1
@@ -1,8 +1,10 @@
 #include "coin.h"
 
 #define F_CTOK(C)	((double)(C))/1000000.0
-#define F_CTOM(C)	F_CTOK(C) *   0.3861
-#define F_CTOA(C)	F_CTOK(C) * 247.1000
+	/* sq km -> sq miles = 1000^2 / (0.0254 * 12 * 5280)^2 */
+#define F_CTOM(C)	F_CTOK(C) *   0.386102158542446
+	/* sq km -> acres = sq miles * 640 */
+#define F_CTOA(C)	F_CTOK(C) * 247.105381467165
 #define F_CTOH(C)	F_CTOK(C) * 100.0000
 
 #define F_CTOP(C,R) ((int)R) ? (double)C / (double)R * 100.0 : 0.0