From 75d9e5bd201123b4094e7c792a04768e9b0d3724 Mon Sep 17 00:00:00 2001
From: oliskoli <oliskoli>
Date: Thu, 24 May 2007 12:01:52 +0000
Subject: [PATCH] gpsmath: Fix problem with conversion from UTM coordinates in
 southern hemisphere.

---
 jeeps/gpsmath.c | 43 +++++++++++++------------------------------
 1 file changed, 13 insertions(+), 30 deletions(-)

diff --git a/jeeps/gpsmath.c b/jeeps/gpsmath.c
index b87de048a..92493c79e 100644
--- a/jeeps/gpsmath.c
+++ b/jeeps/gpsmath.c
@@ -1747,25 +1747,7 @@ static int32 GPS_Math_UTM_Param_To_Mc(int32 zone, char zc, double *Mc,
 int32 GPS_Math_UTM_EN_To_NAD83(double *lat, double *lon, double E,
 			       double N, int32 zone, char zc)
 {
-    double phi0;
-    double lambda0;
-    double N0;
-    double E0;
-    double F0;
-    double a;
-    double b;
-
-    if(!GPS_Math_UTM_Param_To_Mc(zone,zc,&lambda0,&E0,&N0,&F0))
-	return 0;
-
-    phi0 = (double)0.0;
-
-    a = (double) GPS_Ellipse[21].a;
-    b = a - (a/GPS_Ellipse[21].invf);
-
-    GPS_Math_EN_To_LatLon(E,N,lat,lon,N0,E0,phi0,lambda0,F0,a,b);
-
-    return 1;
+    return GPS_Math_UTM_EN_To_Known_Datum(lat, lon, E, N, zone, zc, 77);
 }
 
 
@@ -1786,19 +1768,10 @@ int32 GPS_Math_UTM_EN_To_NAD83(double *lat, double *lon, double E,
 int32 GPS_Math_UTM_EN_To_WGS84(double *lat, double *lon, double E,
 			       double N, int32 zone, char zc)
 {
-    double phi;
-    double lambda;
-    double H;
-
-    if(!GPS_Math_UTM_EN_To_NAD83(&phi,&lambda,E,N,zone,zc))
-	return 0;
-
-    
-    GPS_Math_Known_Datum_To_WGS84_M(phi,lambda,0,lat,lon,&H,77);
-
-    return 1;
+    return GPS_Math_UTM_EN_To_Known_Datum(lat, lon, E, N, zone, zc, 118);
 }
 
+
 /* @func GPS_Math_Known_Datum_To_UTM_EN *********************************
 **
 ** Transform known datum lat/lon to UTM zone, easting and northing
@@ -1865,10 +1838,18 @@ int32 GPS_Math_UTM_EN_To_Known_Datum(double *lat, double *lon, double E,
     double a;
     double b;
     int32  idx;
+    char southern;
 
     if(!GPS_Math_UTM_Param_To_Mc(zone,zc,&lambda0,&E0,&N0,&F0))
 	return 0;
 
+    if (N0 > N) {
+        southern = 1;
+	N = N0 - N;
+	N0 = 0;
+    }
+    else southern = 0;
+
     phi0 = (double)0.0;
 
     idx  = GPS_Datum[n].ellipse;
@@ -1877,6 +1858,8 @@ int32 GPS_Math_UTM_EN_To_Known_Datum(double *lat, double *lon, double E,
 
     GPS_Math_EN_To_LatLon(E,N,lat,lon,N0,E0,phi0,lambda0,F0,a,b);
 
+    if (southern) *lat = -(*lat);
+
     return 1;
 }
 
-- 
2.30.2