This is an automated email from the ASF dual-hosted git repository.
desruisseaux pushed a commit to branch geoapi-4.0
in repository https://gitbox.apache.org/repos/asf/sis.git
commit 4c5e164547b00877b00e7cb60840d5a03ef6d628
Author: Martin Desruisseaux <martin.desruisse...@geomatys.com>
AuthorDate: Mon Feb 7 10:44:32 2022 +0100
Simplify the formulas for φ, ∂y/∂λ and ∂y/∂φ (atan2 replaced by asin).
---
.../operation/transform/PoleRotation.java | 21 ++++++++-------------
.../operation/transform/PoleRotationTest.java | 4 +++-
2 files changed, 11 insertions(+), 14 deletions(-)
diff --git
a/core/sis-referencing/src/main/java/org/apache/sis/referencing/operation/transform/PoleRotation.java
b/core/sis-referencing/src/main/java/org/apache/sis/referencing/operation/transform/PoleRotation.java
index cba2077..4910a94 100644
---
a/core/sis-referencing/src/main/java/org/apache/sis/referencing/operation/transform/PoleRotation.java
+++
b/core/sis-referencing/src/main/java/org/apache/sis/referencing/operation/transform/PoleRotation.java
@@ -42,7 +42,6 @@ import org.apache.sis.util.ComparisonMode;
import org.apache.sis.util.Debug;
import static java.lang.Math.*;
-import static org.apache.sis.internal.referencing.Formulas.fastHypot;
/**
@@ -395,11 +394,9 @@ public class PoleRotation extends AbstractMathTransform2D
implements Serializabl
final double zcosφp = z * cosφp;
final double xt = zcosφp - xsinφp;
final double zt = -xcosφp - zsinφp;
- final double r2 = xt*xt + y2; // yt = y in ihis algorithm.
- final double r = sqrt(r2); // The slower hypot(…) is not
needed because values are close to 1.
if (dstPts != null) {
dstPts[dstOff] = atan2(y, xt);
- dstPts[dstOff+1] = atan2(zt, r);
+ dstPts[dstOff+1] = asin(zt);
}
if (!derivate) {
return null;
@@ -410,16 +407,15 @@ public class PoleRotation extends AbstractMathTransform2D
implements Serializabl
*
* https://svn.apache.org/repos/asf/sis/analysis/Rotated%20pole.wxmx
*/
+ final double r2 = xt*xt + y2; // yt = y in ihis algorithm.
+ final double zr = sqrt(1 - zt*zt);
final double dxφ = cosλ * zsinφp + cosφ * cosφp;
final double dyφ = cosλ * zcosφp - cosφ * sinφp;
- final double zλ = z * sinλ;
- final double zr = zt / r;
- final double rc = r2 + zt*zt;
return new Matrix2(
- (xt*x - y2*sinφp) / r2, // ∂x/∂λ
- -(xt*zλ + y*dxφ) / r2, // ∂x/∂φ
- (r*cosφp - zr*(x + sinφp*xt))*y / rc, // ∂y/∂λ
- (r*dyφ + zr*(y*zλ - dxφ*xt)) / rc); // ∂y/∂φ
+ (xt*x - y2*sinφp) / r2, // ∂x/∂λ
+ -(xt*z*sinλ + y*dxφ) / r2, // ∂x/∂φ
+ y*cosφp / zr, // ∂y/∂λ
+ dyφ / zr); // ∂y/∂φ
}
/**
@@ -446,9 +442,8 @@ public class PoleRotation extends AbstractMathTransform2D
implements Serializabl
double x = cos(λ) * cosφ;
double xt = cosφp * z - sinφp * x;
double zt = -cosφp * x - sinφp * z;
- double r = fastHypot(xt, y);
dstPts[dstOff++] = atan2(y, xt);
- dstPts[dstOff++] = atan2(zt, r);
+ dstPts[dstOff++] = asin(zt);
}
}
diff --git
a/core/sis-referencing/src/test/java/org/apache/sis/referencing/operation/transform/PoleRotationTest.java
b/core/sis-referencing/src/test/java/org/apache/sis/referencing/operation/transform/PoleRotationTest.java
index bb0525e..f346857 100644
---
a/core/sis-referencing/src/test/java/org/apache/sis/referencing/operation/transform/PoleRotationTest.java
+++
b/core/sis-referencing/src/test/java/org/apache/sis/referencing/operation/transform/PoleRotationTest.java
@@ -255,9 +255,11 @@ public final strictfp class PoleRotationTest extends
MathTransformTestCase {
*
* {@preformat shell
* cs2cs -I -E -f %g "EPSG:4326" +to +type=crs +proj=ob_tran
+o_proj=longlat +datum=WGS84 +no_defs \
- * +o_lat_p=70 +o_lon_p=40 +lon_0=10 coords.txt
+ * +o_lat_p=70 +o_lon_p=40 +lon_0=190 coords.txt
* }
*
+ * Note that a 180° offset must be added to the {@code +lon_0} parameter.
+ *
* @throws FactoryException if the transform can not be created.
* @throws TransformException if an error occurred while transforming a
point.
*/
