Merge pull request #3993 from mapfish/ghci/backport/3979-to-3.32

[Backport 3.32] Correct geodetic scale denominator calculation

Author: sbrunner

core/src/main/java/org/mapfish/print/map/Scale.java

@@ -201,7 +201,7 @@ public double getGeodeticDenominator(
       double width = 1;
       double geoWidthInches = getResolutionInInches() * width;
       double geoWidth = DistanceUnit.IN.convertTo(geoWidthInches, this.unit);
-      double minGeoX = position.y - (geoWidth / 2.0);
+      double minGeoX = position.x - (geoWidth / 2.0);
       double maxGeoX = minGeoX + geoWidth;
 
       final GeodeticCalculator calculator = new GeodeticCalculator(projection);

core/src/test/java/org/mapfish/print/map/ScaleTest.java

@@ -12,6 +12,7 @@
 public class ScaleTest {
   public static final CoordinateReferenceSystem SPHERICAL_MERCATOR;
   public static final CoordinateReferenceSystem CH1903;
+  public static final CoordinateReferenceSystem CH2056;
   private static final double DELTA = 0.00001;
   private static final double SCALE = 108335.72891406555;
   private static final double RESOLUTION = 38.21843770023979;
@@ -20,6 +21,7 @@ public class ScaleTest {
     try {
       SPHERICAL_MERCATOR = CRS.decode("EPSG:3857");
       CH1903 = CRS.decode("EPSG:21781");
+      CH2056 = CRS.decode("EPSG:2056");
     } catch (FactoryException e) {
       throw new RuntimeException(e);
     }
@@ -47,4 +49,29 @@ public void geodetic() {
         10019.0,
         1.0);
   }
+
+  /**
+   * This test verifies that the geodetic scale calculation correctly uses position.x for the
+   * horizontal coordinate. In projections like CH2056 (Swiss Oblique Mercator) or UTM, shifting a
+   * point in X direction while keeping Y constant affects the geodetic distance, unlike EPSG:3857
+   * where distortion is primarily latitude-dependent.
+   *
+   * <p>With some other projection like EPSG:5936 WGS 84 / EPSG Alaska Polar Stereographic The
+   * defferance will consequant.
+   */
+  @Test
+  public void geodeticCH2056XPositionDependence() {
+    final Scale scale = new Scale(25000.0, CH2056, PDF_DPI);
+
+    // Calculate geodetic scale at two positions with same Y but different X
+    // Using coordinates in CH2056 CRS (EPSG:2056)
+    final Coordinate positionRef = new Coordinate(2600000.0, 1200000.0);
+    final Coordinate positionLeft = new Coordinate(2484274.0, 1200000.0);
+
+    final double geodeticScaleRef = scale.getGeodeticDenominator(CH2056, PDF_DPI, positionRef);
+    final double geodeticScaleLeft = scale.getGeodeticDenominator(CH2056, PDF_DPI, positionLeft);
+
+    assertEquals(24996.77190700038, geodeticScaleRef, 0.0);
+    assertEquals(24996.76743516703, geodeticScaleLeft, 0.0);
+  }
 }