Use atan2 rather than atan when calculating longitude after Helmert t…

…ransform to ensure the co-ordinate ends up in the right quadrant. Fixes #4, fixes #5

LatLng.php

@@ -277,7 +277,7 @@ public function transformDatum(RefEll $aFromEllipsoid, RefEll $aToEllipsoid, $aT
  $b = $aToEllipsoid->min;
  $eSquared = $aToEllipsoid->ecc;
 
- $lambdaB = rad2deg(atan($yB / $xB));
+ $lambdaB = rad2deg(atan2($yB, $xB));
  $p = sqrt(($xB * $xB) + ($yB * $yB));
  $phiN = atan($zB / ($p * (1 - $eSquared)));
  for ($i = 1; $i < 10; $i++) {

README.md

@@ -30,7 +30,9 @@ Output of calculations have been changed from the original code in the following
  * When calculating surface distances, a more accurate mean radius is now used rather than
  that derived from historical definitions of a nautical mile 
  * Corrected calculation of OS 6-figure grid references (rounding instead of truncating meant the
- grid square was sometimes off by 1) 
+ grid square was sometimes off by 1)
+ * Corrected issue with Helmert transform where the resulting co-ordinate could be placed into
+ the wrong quadrant
 
 Usage
 -----
@@ -57,4 +59,4 @@ Requirements
 
 License
 -------
-The original PHPcoord is GPL-licensed, and this version inherits that. Terms can be found at http://www.gnu.org/licenses/gpl.html 
+The original PHPcoord is GPL-licensed, and this version inherits that. Terms can be found at http://www.gnu.org/licenses/gpl.html 

tests/LatLngTest.php

@@ -198,4 +198,70 @@ public function testDistanceDifferentEllipsoids() {
  self::assertEquals($expected, $work->distance($charingCross));
  }
 
- }
+ public function testNoopTransformSanFrancisco()
+ {
+ $LatLng = new LatLng(37.783333, -122.416667);
+ $LatLngTrans=clone $LatLng;
+
+ $LatLngTrans->transformDatum(RefEll::GRS80(), RefEll::GRS80(), 0, 0, 0, 0, 0, 0, 0);
+
+ $this->assertEquals($LatLng->lat,$LatLngTrans->lat,'Latitude transform failed');
+ $this->assertEquals($LatLng->lng,$LatLngTrans->lng,'Longitude transform failed');
+ }
+
+ public function testNoopTransformSydney()
+ {
+ $LatLng = new LatLng(-33.859972, 151.211111);
+ $LatLngTrans=clone $LatLng;
+
+ $LatLngTrans->transformDatum(RefEll::GRS80(), RefEll::GRS80(), 0, 0, 0, 0, 0, 0, 0);
+
+ $this->assertEquals($LatLng->lat,$LatLngTrans->lat,'Latitude transform failed');
+ $this->assertEquals($LatLng->lng,$LatLngTrans->lng,'Longitude transform failed');
+ }
+
+ public function testNoopTransformLondon()
+ {
+ $LatLng = new LatLng(51.54105, -0.12319);
+ $LatLngTrans=clone $LatLng;
+
+ $LatLngTrans->transformDatum(RefEll::GRS80(), RefEll::GRS80(), 0, 0, 0, 0, 0, 0, 0);
+
+ $this->assertEquals($LatLng->lat,$LatLngTrans->lat,'Latitude transform failed');
+ $this->assertEquals($LatLng->lng,$LatLngTrans->lng,'Longitude transform failed');
+ }
+
+ public function testNoopTransformTokyo()
+ {
+ $LatLng = new LatLng(35.694668, 139.693122);
+ $LatLngTrans=clone $LatLng;
+
+ $LatLngTrans->transformDatum(RefEll::GRS80(), RefEll::GRS80(), 0, 0, 0, 0, 0, 0, 0);
+
+ $this->assertEquals($LatLng->lat,$LatLngTrans->lat,'Latitude transform failed');
+ $this->assertEquals($LatLng->lng,$LatLngTrans->lng,'Longitude transform failed');
+ }
+
+ public function testNoopTransformCapeTown()
+ {
+ $LatLng = new LatLng(-33.925278, 18.423889);
+ $LatLngTrans=clone $LatLng;
+
+ $LatLngTrans->transformDatum(RefEll::GRS80(), RefEll::GRS80(), 0, 0, 0, 0, 0, 0, 0);
+
+ $this->assertEquals($LatLng->lat,$LatLngTrans->lat,'Latitude transform failed');
+ $this->assertEquals($LatLng->lng,$LatLngTrans->lng,'Longitude transform failed');
+ }
+
+ public function testNoopTransformNewYork()
+ {
+ $LatLng = new LatLng(40.7127, -74.0059);
+ $LatLngTrans=clone $LatLng;
+
+ $LatLngTrans->transformDatum(RefEll::GRS80(), RefEll::GRS80(), 0, 0, 0, 0, 0, 0, 0);
+
+ $this->assertEquals($LatLng->lat,$LatLngTrans->lat,'Latitude transform failed');
+ $this->assertEquals($LatLng->lng,$LatLngTrans->lng,'Longitude transform failed');
+ }
+
+}