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From desruisse...@apache.org
Subject [sis] 06/09: refactor (referencing satellite-tracking projections) : Method used by both (cylindrical and conic) direct transformation of the Satellite-tracking projections to compute the L coefficient and its partial derivate dL_dφ if queried. Test passed for both transformation and testDerivativeOnSphere.
Date Tue, 01 Oct 2019 17:25:17 GMT
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 8c2d72d85ff84114983ef2e1f62cd2cf5e538585
Author: Matthieu_Bastianelli <matthieu.bastianelli@geomatys.com>
AuthorDate: Thu Jul 25 12:18:37 2019 +0200

    refactor (referencing satellite-tracking projections) : Method used by both (cylindrical
and conic) direct transformation of the Satellite-tracking projections to  compute the L coefficient
and its partial derivate dL_dφ if queried. Test passed for both transformation and testDerivativeOnSphere.
---
 .../projection/ConicSatelliteTracking.java         | 61 ++++++++++++++++------
 .../projection/CylindricalSatelliteTracking.java   | 17 +++---
 2 files changed, 50 insertions(+), 28 deletions(-)

diff --git a/core/sis-referencing/src/main/java/org/apache/sis/referencing/operation/projection/ConicSatelliteTracking.java
b/core/sis-referencing/src/main/java/org/apache/sis/referencing/operation/projection/ConicSatelliteTracking.java
index 9b0b0b0..d265ae2 100644
--- a/core/sis-referencing/src/main/java/org/apache/sis/referencing/operation/projection/ConicSatelliteTracking.java
+++ b/core/sis-referencing/src/main/java/org/apache/sis/referencing/operation/projection/ConicSatelliteTracking.java
@@ -285,13 +285,9 @@ public class ConicSatelliteTracking extends NormalizedProjection{
             throw new ProjectionException(Resources.format(Resources.Keys.CanNotTransformCoordinates_2));
         }
 
-        final double sin_φ  = sin(φ);
-        final double sinφ_sini = sin_φ / sin_i;
-        final double dλ     = -asin(sinφ_sini);
-        final double tan_dλ = tan(dλ);
-        final double λt     = atan(tan_dλ * cos_i);
-        final double L      = λt - p2_on_p1 * dλ;
-
+        // compute an double array with {L} or {L, dL/dφ} if derivate recquired.
+        final double[] vector_L = computeLanddLdφForDirectTransform(φ, derivate);
+        final double L = vector_L[0];
         /*
          * As {@code latitudeLimit} is an approximation we repeat the test here.
          */
@@ -301,17 +297,15 @@ public class ConicSatelliteTracking extends NormalizedProjection{
             throw new ProjectionException(Resources.format(Resources.Keys.CanNotTransformCoordinates_2));
         }
 
-        final double nLandS0 = n*L+s0;
+        final double nLandS0     = n*L+s0;
         final double sin_nLandS0 = sin(nLandS0);
-
-        final double ρ      = cosφ1xsinF1_n/sin_nLandS0;
-//        final double ρ      = 1/sin(n*L+s0);
+        final double ρ           = cosφ1xsinF1_n/sin_nLandS0;
 
         final double sinλ = sin(λ);
         final double cosλ = cos(λ);
         if (dstPts != null) {
-            dstPts[dstOff    ] = ρ * sinλ;   // x
-            dstPts[dstOff + 1] = - ρ*cosλ;   // y
+            dstPts[dstOff    ] =   ρ * sinλ;   // x
+            dstPts[dstOff + 1] = - ρ * cosλ;   // y
         }
 
          if (!derivate) {
@@ -320,14 +314,12 @@ public class ConicSatelliteTracking extends NormalizedProjection{
 
         //=========================To check the resolution =====================
         final double dρ_dφ = cosφ1xsinF1_n  * (-1 / (sin_nLandS0*sin_nLandS0)) *cos(nLandS0)
 * n
-                // dL/dφ :
-                * ((cos(φ) / sin_i) *(1/sqrt(1-sinφ_sini*sinφ_sini)))  // derivative of
(-dλ/dφ)
-                * ( p2_on_p1 - ((1+tan_dλ*tan_dλ)*cos_i/(1+λt*λt) ) );
+                * vector_L[1]; // dL/dφ
 
         final double dx_dλ = ρ*cosλ;
         final double dx_dφ = sinλ * dρ_dφ;
 
-        final double dy_dλ =  ρ*sinλ;
+        final double dy_dλ = ρ*sinλ;
         final double dy_dφ = -cosλ * dρ_dφ;
         //======================================================================
 
@@ -445,4 +437,39 @@ public class ConicSatelliteTracking extends NormalizedProjection{
         return atan(tan(dλn) * cos_i); // eq.28-3a in Snyder
     }
 
+    /**
+     * Method returning the L coefficient used for the direct transformation of
+     * the Satellite-tracking projections and its partial derivate dL_dφ if
+     * queried by a true value of the input parameter derivate.
+     *
+     * This method is used By :
+     *     {@link ConicSatelliteTracking#transform(double[], int, double[], int, boolean)
}
+     * and {@link CylindricalSatelliteTracking#transform(double[], int, double[], int, boolean)
}
+     *
+     * @param φ : input latitude of the projection's (direct)  method.
+     * @param derivate : boolean value indicating if the partial derivate dL_dφ
+     *                  must be computed.
+     * @return a double array. It contains :
+     *        - if derivate is false :  only the L coefficient value.
+     *        - if derivate is true :  the L coefficient value and the partial
+     *          derivate dL_dφ respectively at the at index 0 and 1 of the
+     *          resulting array.
+     */
+    double[] computeLanddLdφForDirectTransform(final double φ, final boolean derivate){
+
+        final double sinφ_sini = sin(φ) / sin_i;
+        final double dλ        = -asin(sinφ_sini);
+        final double tan_dλ    = tan(dλ);
+        final double λt        = atan(tan_dλ * cos_i);
+        final double L         = λt - p2_on_p1 * dλ;
+
+        if (derivate){
+            final double dL_dφ = ((cos(φ) / sin_i) *(1/sqrt(1-sinφ_sini*sinφ_sini)))
 // first computed term associated with derivative of (-dλ/dφ)
+                               * ( p2_on_p1 - ((1+tan_dλ*tan_dλ)*cos_i/(1+λt*λt) ) );
+            return new double[] {L, dL_dφ};
+        } else {
+            return new double[] {L};
+        }
+    }
+
 }
diff --git a/core/sis-referencing/src/main/java/org/apache/sis/referencing/operation/projection/CylindricalSatelliteTracking.java
b/core/sis-referencing/src/main/java/org/apache/sis/referencing/operation/projection/CylindricalSatelliteTracking.java
index 9348834..4348993 100644
--- a/core/sis-referencing/src/main/java/org/apache/sis/referencing/operation/projection/CylindricalSatelliteTracking.java
+++ b/core/sis-referencing/src/main/java/org/apache/sis/referencing/operation/projection/CylindricalSatelliteTracking.java
@@ -127,21 +127,17 @@ public class CylindricalSatelliteTracking extends ConicSatelliteTracking
{
         final double φ = srcPts[srcOff + 1];
 
         // TODO : check the condition and the thrown exception.
-        if (abs(φ) > PI / 2 - abs(PI / 2 - i)) {  // Exceed tracking limit
+            // if (abs(φ) > PI / 2 - abs(PI - i)) {  // Exceed tracking limit
+        if (φ > PI - i) {  // Exceed tracking limit
             throw new ProjectionException(Resources.format(Resources.Keys.CanNotTransformCoordinates_2));
         }
 
-        final double sin_φ  = sin(φ);
-        final double sinφ_sini = sin_φ / sin_i;
-
-        final double dλ     = -asin(sin_φ / sin_i);
-        final double tan_dλ = tan(dλ);
-        final double λt     = atan(tan(dλ) * cos_i);
-        final double L      = λt - p2_on_p1 * dλ;
+        // compute an double array with {L} or {L, dL/dφ} if derivate recquired.
+        final double[] vector_L = computeLanddLdφForDirectTransform(φ, derivate);
 
         if (dstPts != null) {
             dstPts[dstOff    ] = λ;   // In eq. Snyder 28-5 : R(λ - λ0) cos_φ1
-            dstPts[dstOff + 1] = L;   // In eq. Snyder 28-6 : R L cos(φ1)/F'1
+            dstPts[dstOff + 1] = vector_L[0];   // In eq. Snyder 28-6 : R L cos(φ1)/F'1
         }
 
         /* =====================================================================
@@ -162,8 +158,7 @@ public class CylindricalSatelliteTracking extends ConicSatelliteTracking
{
         final double dx_dφ = 0;
 
         final double dy_dλ = 0;
-        final double dy_dφ = ((cos(φ) / sin_i) *(1/sqrt(1-sinφ_sini*sinφ_sini)))  //
derivative of (-dλ/dφ)
-                * ( p2_on_p1 - ((1+tan_dλ*tan_dλ)*cos_i/(1+λt*λt) ) );
+        final double dy_dφ = vector_L[1]; //dL/dφ
         //======================================================================
 
         return new Matrix2(dx_dλ, dx_dφ,


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