Added support for National Yard Grid

Support National Yard Grid (tested now!)
Ritchie333 · Sep 19, 2024 · bb45506 · bb45506
1 parent 58774fe
commit bb45506
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Showing 4 changed files with 19 additions and 5 deletions.
diff --git a/src/CopyPixels.cpp b/src/CopyPixels.cpp
@@ -90,8 +90,10 @@ void CopyPixelsWithOSYMask::UpdateBoundingBox(const char *mapref)
 	int dEasting = 0, dNorthing = 0;
 	if (2 == sscanf(mapref, "%d:%d", &dEasting, &dNorthing))
 	{
-		dEasting *= METRES_IN_YARD;
-		dNorthing *= METRES_IN_YARD;
+		int me = 0, mn = 0;
+		YardsToMetres( dEasting, dNorthing, me, mn );
+		dEasting = me;
+		dNorthing = mn;
 		if (!boxset || gsouth > dNorthing)
 			gsouth = dNorthing;
 		if (!boxset || gnorth < dNorthing)

diff --git a/src/WarpOs.cpp b/src/WarpOs.cpp
@@ -71,6 +71,7 @@ const Point ProjRefToOutImg(const Point& ref, PolyProjectArgs::ProjType projType
 {
 	class PolyProjectArgs *args = (class PolyProjectArgs *)userPtr;
 	double lat = 0.0, lon = 0.0, alt = 0.0;
+	int me = 0, mn = 0;
 	switch (projType)
 	{
 	case PolyProjectArgs::OSGB:
@@ -95,7 +96,8 @@ const Point ProjRefToOutImg(const Point& ref, PolyProjectArgs::ProjType projType
 		}
 		break;
 	case PolyProjectArgs::OSGBY:
-		gFallbackConverter.ConvertGbos1936ToWgs84(ref.x * METRES_IN_YARD, ref.y * METRES_IN_YARD, 0.0, lat, lon, alt);
+		YardsToMetres( ref.x, ref.y, me, mn );
+		gFallbackConverter.ConvertGbos1936ToWgs84(me, mn, 0.0, lat, lon, alt);
 		break;
 
 	case PolyProjectArgs::Mercator:
@@ -456,8 +458,10 @@ int main(int argc, char *argv[])
 			{
 				string mapref = line[1].GetVals();
 				sscanf(mapref.c_str(), "%d:%d", &dEasting, &dNorthing);
+				int me = 0, mn = 0;
+				YardsToMetres( dEasting, dNorthing, me, mn );
 				// Add point to transform constraints
-				gConverter.ConvertGbos1936ToWgs84(dEasting * METRES_IN_YARD, dNorthing * METRES_IN_YARD, 0.0, lat, lon, alt);
+				gConverter.ConvertGbos1936ToWgs84(me, mn, 0.0, lat, lon, alt);
 			}
 			if (strcmp(line[0].GetVals(), "osi") == 0)
 			{

diff --git a/src/gbos1936/Gbos1936.cpp b/src/gbos1936/Gbos1936.cpp
@@ -745,6 +745,12 @@ Function TrueAzimuth(AtEast, AtNorth, ToEast, ToNorth, a, b, e0, n0, f0, PHI0)
 
 End Function*/
 
+void YardsToMetres( const int ine, const int inn, int& oute, int& outn )
+{
+    oute = ( ( ine - 1000000 ) * METRES_IN_YARD ) + 400000;
+    outn = ( ( inn - 1000000 ) * METRES_IN_YARD ) - 100000;
+}
+
 void ConvertCasToGeo(double ea, double no, double he,
                        double &latOut, double &lonOut, double &heOut,
                        const GridData& CSGrid )

diff --git a/src/gbos1936/Gbos1936.h b/src/gbos1936/Gbos1936.h
@@ -17,7 +17,7 @@
 #define PARIS_CENTRE_LON 2.336506
 
 const double METRES_IN_MILE = 1609.347955248;
-const double METRES_IN_YARD = 0.9144022473;
+const double METRES_IN_YARD = 0.9144;
 
 struct Ellip
 {
@@ -101,6 +101,8 @@ double E_N_to_Lat(double East, double North, double a, double b, double e0, doub
 double E_N_to_Long(double East, double North, double a, double b, double e0, double n0, double f0, double PHI0, double LAM0);
 double calc_M(long double latdiff, long double latsum, long double nn, long double eb, double F0);
 
+void YardsToMetres( const int ine, const int inn, int& oute, int& outn );
+
 void TM2Geo( double East, double North, const GridData& TMgrid, double& latOut, double& lngOut );
 void Geo2TM( double lat, double lon, const GridData& TMgrid, double &eaOut, double &noOut );
 void Geo2Geo( double lat, double lon, const struct Datum& datum_a, const struct Datum& datum_b, double& latOut, double &lngOut );