fix: unit conversion and indexing

advection/src/AdvectionKernel.h

@@ -11,7 +11,7 @@
  */
 class AdvectionKernel {
 public:
-    const static int DT = 50;
+    const static int DT = 100000; // Seconds
     /**
      * This function must take a time, latitude and longitude of a particle and must output
      * a new latitude and longitude after being advected once for AdvectionKernel::DT time as defined above.
@@ -22,6 +22,11 @@ public:
      */
     virtual std::pair<double, double> advect(int time, double latitude, double longitude) const = 0;
 
+    // Taken from Parcels https://github.com/OceanParcels/parcels/blob/daa4b062ed8ae0b2be3d87367d6b45599d6f95db/parcels/tools/converters.py#L155
+    const static double metreToDegrees(double metre) {
+        return metre / 1000. / 1.852 / 60.;
+    }
+
 };
 
 #endif //ADVECTION_ADVECTIONKERNEL_H

advection/src/RK4AdvectionKernel.cpp

@@ -8,28 +8,28 @@ RK4AdvectionKernel::RK4AdvectionKernel(std::shared_ptr<UVGrid> grid): grid(grid)
 std::pair<double, double> RK4AdvectionKernel::advect(int time, double latitude, double longitude) const {
     auto [u1, v1] = bilinearinterpolation(*grid, time, latitude, longitude);
 //    lon1, lat1 = (particle.lon + u1*.5*particle.dt, particle.lat + v1*.5*particle.dt);
-    double lon1 = longitude + v1 * .5*DT;
-    double lat1 = latitude + u1*.5*DT;
+    double lon1 = longitude + metreToDegrees(v1 * 0.5*DT);
+    double lat1 = latitude + metreToDegrees(u1 * 0.5*DT);
 
 //    (u2, v2) = fieldset.UV[time + .5 * particle.dt, particle.depth, lat1, lon1, particle]
     auto [u2, v2] = bilinearinterpolation(*grid, time + 0.5*DT, lat1, lon1);
 
 //    lon2, lat2 = (particle.lon + u2*.5*particle.dt, particle.lat + v2*.5*particle.dt)
-    double lon2 = longitude + v2 * 0.5 * DT;
-    double lat2 = latitude + u2 * 0.5 * DT;
+    double lon2 = longitude + metreToDegrees(v2 * 0.5 * DT);
+    double lat2 = latitude + metreToDegrees(u2 * 0.5 * DT);
 
 //    (u3, v3) = fieldset.UV[time + .5 * particle.dt, particle.depth, lat2, lon2, particle]
     auto [u3, v3] = bilinearinterpolation(*grid, time + 0.5 * DT, lat2, lon2);
 
 //    lon3, lat3 = (particle.lon + u3*particle.dt, particle.lat + v3*particle.dt)
-    double lon3 = longitude + v3 * DT;
-    double lat3 = latitude + u3 * DT;
+    double lon3 = longitude + metreToDegrees(v3 * DT);
+    double lat3 = latitude + metreToDegrees(u3 * DT);
 
 //    (u4, v4) = fieldset.UV[time + particle.dt, particle.depth, lat3, lon3, particle]
     auto [u4, v4] = bilinearinterpolation(*grid, time + DT, lat3, lon3);
 
-    double lonFinal = longitude + (v1 + 2 * v2 + 2 * v3 + v4) / 6.0 * DT;
-    double latFinal = latitude + (u1 + 2 * u2 + 2 * u3 + u4) / 6.0 * DT;
+    double lonFinal = longitude + metreToDegrees((v1 + 2 * v2 + 2 * v3 + v4) / 6.0 * DT);
+    double latFinal = latitude + metreToDegrees((u1 + 2 * u2 + 2 * u3 + u4) / 6.0 * DT);
 
     return {latFinal, lonFinal};
 }

advection/src/RK4AdvectionKernel.h

@@ -1,7 +1,6 @@
 #ifndef ADVECTION_RK4ADVECTIONKERNEL_H
 #define ADVECTION_RK4ADVECTIONKERNEL_H
 
-
 #include "AdvectionKernel.h"
 #include "UVGrid.h"
 

advection/src/UVGrid.cpp

@@ -39,7 +39,7 @@ const Vel &UVGrid::operator[](size_t timeIndex, size_t latIndex, size_t lonIndex
         or lonIndex < 0 or lonIndex >= lonSize) {
         throw std::out_of_range("Index out of bounds");
     }
-    size_t index = timeIndex * (latSize * lonSize) + latIndex * lonIndex + lonIndex;
+    size_t index = timeIndex * (latSize * lonSize) + latIndex * lonSize + lonIndex;
     return uvData[index];
 }
 
@@ -63,4 +63,4 @@ void UVGrid::streamSlice(ostream &os, size_t t) {
         }
       os << endl;
     }
-}
+}

advection/src/UVGrid.h

@@ -49,7 +49,7 @@ public:
     std::vector<double> lons;
 
     /**
-     * The 3D index into the data
+     * The 3D index into the data. The array is sized by [8761][67][116]
      * @return Velocity at that index
      */
     const Vel& operator[](size_t timeIndex, size_t latIndex, size_t lonIndex) const;

advection/src/main.cpp

@@ -1,43 +1,89 @@
+#include <ranges>
+#include <iomanip>
+#include <stdexcept>
+
 #include "interpolate.h"
 #include "Vel.h"
 #include "EulerAdvectionKernel.h"
 #include "RK4AdvectionKernel.h"
-#include <ranges>
-#include <chrono>
+#include "interpolate.h"
 
 #define NotAKernelError "Template parameter T must derive from AdvectionKernel"
 
 using namespace std;
 
 template <typename AdvectionKernelImpl>
-void advectForSomeTime(const UVGrid &uvGrid, const AdvectionKernelImpl &kernel, double latstart, double lonstart) {
+void advectForSomeTime(const UVGrid &uvGrid, const AdvectionKernelImpl &kernel, double latstart, double lonstart, int i, char colour[10]) {
 
     // Require at compile time that kernel derives from the abstract class AdvectionKernel
     static_assert(std::is_base_of<AdvectionKernel, AdvectionKernelImpl>::value, NotAKernelError);
 
     double lat1 = latstart, lon1 = lonstart;
-    for(int time = 100; time <= 10000; time += AdvectionKernel::DT) {
-        cout << "lat = " << lat1 << " lon = " << lon1 << endl;
-        auto [templat, templon] = kernel.advect(time, lat1, lon1);
-        lat1 = templat;
-        lon1 = templon;
+    for(int time = 0; time <= 31536000.; time += AdvectionKernel::DT) {
+//        cout << setprecision(8) << lat1 << "," << setprecision(8) << lon1 << ",end" << i << "," << colour << endl;
+        try {
+            auto [templat, templon] = kernel.advect(time, lat1, lon1);
+            lat1 = templat;
+            lon1 = templon;
+        } catch (const out_of_range& e) {
+            cerr << "broke out of loop!" << endl;
+            break;
+        }
     }
+    cout << setprecision(8) << latstart << "," << setprecision(8) << lonstart << ",begin" << i << "," << colour << endl;
+    cout << setprecision(8) << lat1 << "," << setprecision(8) << lon1 << ",end" << i << "," << colour << endl;
 }
 
+void testGridIndexing(const UVGrid *uvGrid) {
+    int time = 20000;
+    cout << "=== land === (should all give 0)" << endl;
+    cout << bilinearinterpolation(*uvGrid, time, 53.80956379699079, -1.6496306344654406) << endl;
+    cout << bilinearinterpolation(*uvGrid, time, 55.31428895563707, -2.851581041325997) << endl;
+    cout << bilinearinterpolation(*uvGrid, time, 47.71548983067583, -1.8704054037408626) << endl;
+    cout << bilinearinterpolation(*uvGrid, time, 56.23521060314398, 8.505979324950573) << endl;
+    cout << bilinearinterpolation(*uvGrid, time, 53.135645440244375, 8.505979324950573) << endl;
+    cout << bilinearinterpolation(*uvGrid, time, 56.44761278775708, -4.140629303756164) << endl;
+    cout << bilinearinterpolation(*uvGrid, time, 52.67625153110339, 0.8978569759455872) << endl;
+    cout << bilinearinterpolation(*uvGrid, time, 52.07154079279377, 4.627951041411331) << endl;
+
+    cout << "=== ocean === (should give not 0)" << endl;
+    cout << bilinearinterpolation(*uvGrid, time, 47.43923166616274, -4.985451481829083) << endl;
+    cout << bilinearinterpolation(*uvGrid, time, 50.68943556852362, -9.306162999561733) << endl;
+    cout << bilinearinterpolation(*uvGrid, time, 53.70606799886677, -4.518347647034465) << endl;
+    cout << bilinearinterpolation(*uvGrid, time, 60.57987114267971, -12.208262973672621) << endl;
+    cout << bilinearinterpolation(*uvGrid, time, 46.532221548197285, -13.408189172582638) << endl;
+    cout << bilinearinterpolation(*uvGrid, time, 50.92725094937812, 1.3975824052375256) << endl;
+    cout << bilinearinterpolation(*uvGrid, time, 51.4028921682209, 2.4059571950925203) << endl;
+    cout << bilinearinterpolation(*uvGrid, time, 53.448445236769004, 0.7996966058017515) << endl;
+//    cout << bilinearinterpolation(*uvGrid, time, ) << endl;
+}
 
 int main() {
     std::shared_ptr<UVGrid> uvGrid = std::make_shared<UVGrid>();
 
-    EulerAdvectionKernel kernelEuler = EulerAdvectionKernel(uvGrid);
+    uvGrid->streamSlice(cout, 900);
 
     RK4AdvectionKernel kernelRK4 = RK4AdvectionKernel(uvGrid);
 
-    double latstart = 52.881770, lonstart = 3.079979;
-
-    cout << "======= Euler Integration =======" << endl;
-    advectForSomeTime(*uvGrid, kernelEuler, latstart, lonstart);
+//    You can use https://maps.co/gis/ to visualise these points
     cout << "======= RK4 Integration =======" << endl;
-    advectForSomeTime(*uvGrid, kernelRK4, latstart, lonstart);
+    advectForSomeTime(*uvGrid, kernelRK4, 54.331795276466615, 4.845871408626273, 0, "#ADD8E6");
+    advectForSomeTime(*uvGrid, kernelRK4, 59.17208978388813, 0.32865481669722213, 1, "#DC143C");
+    advectForSomeTime(*uvGrid, kernelRK4, 56.18661322856813, -9.521463269751877, 2, "#50C878");
+    advectForSomeTime(*uvGrid, kernelRK4, 46.6048774007515, -2.8605696406405947, 3, "#FFEA00");
+    advectForSomeTime(*uvGrid, kernelRK4, 51.45431808648367, 1.6682437444140332, 4, "#663399");
+    advectForSomeTime(*uvGrid, kernelRK4, 51.184757012016085, -6.418923014612084, 5, "#FFA500");
+    advectForSomeTime(*uvGrid, kernelRK4, 54.48325546269538, 7.167517140551792, 6, "#008080");
+    advectForSomeTime(*uvGrid, kernelRK4, 55.43253322410253, -1.1712503620884716, 7, "#FFB6C1");
+    advectForSomeTime(*uvGrid, kernelRK4, 48.852815074172085, 3.4294489497130516, 8, "#36454F"); // on land
+    advectForSomeTime(*uvGrid, kernelRK4, 58.02431905976983, 1.6892571305388995, 9, "#1E90FF"); // Dodger Blue
+    advectForSomeTime(*uvGrid, kernelRK4, 58.99404571805297, 3.4121513161325425, 10, "#FFD700"); // Gold
+    advectForSomeTime(*uvGrid, kernelRK4, 59.51039243098509, -1.6674160241521663, 11, "#6A5ACD"); // Slate Blue
+    advectForSomeTime(*uvGrid, kernelRK4, 60.51250220636489, 1.020893006817227, 12, "#20B2AA"); // Light Sea Green
+    advectForSomeTime(*uvGrid, kernelRK4, 60.38797801281417, 3.516119068711471, 13, "#FF69B4"); // Hot Pink
+    advectForSomeTime(*uvGrid, kernelRK4, 60.02637651315464, -2.4546004365354697, 14, "#800080"); // Purple
+    advectForSomeTime(*uvGrid, kernelRK4, 58.732929454411305, 3.649791893455804, 15, "#FF4500"); // Orange Red
+//    advectForSomeTime(*uvGrid, kernelRK4, ,0);
 
     return 0;
 }