Further clarifications.

core/src/main/java/org/orekit/rugged/raster/TileUpdater.java

@@ -53,23 +53,23 @@ public interface TileUpdater {
      *   </li>
      *   <li>
      *     As elevations are interpolated within Digital Elevation Model
-     *     pixels using four pixels at indices (i, j), (i+1, j), (i, j+1)
-     *     (i+1, j+1). A point in the northernmost row (resp. easternmost
-     *     column) miss neighboring points at row j+1 (resp. neighboring
-     *     points at column i+1) and therefore cannot be interpolated.
-     *     The method should therefore select the northernmost tile if the
-     *     specified latitude is in the overlapping row between two tiles,
-     *     and it should select the easternmost tile if the specified longitude
-     *     is in the overlapping column between two tiles. Failing to do so will
-     *     trigger an error at caller level mentioning the missing required
-     *     neighbors.
+     *     pixels using four pixels at indices (kLat, kLon), (kLat+1, kLon),
+     *     (kLat, kLon+1), (kLat+1, kLon+1). A point in the northernmost row
+     *     (resp. easternmost column) miss neighboring points at row kLat+1
+     *     (resp. neighboring points at column kLon+1) and therefore cannot
+     *     be interpolated. The method should therefore select the northernmost
+     *     tile if the specified latitude is in the overlapping row between two
+     *     tiles, and it should select the easternmost tile if the specified
+     *     longitude is in the overlapping column between two tiles. Failing
+     *     to do so will trigger an error at caller level mentioning the missing
+     *     required neighbors.
      *   </li>
      *   <li>
      *     The elevation at grid point as set when calling {@link
-     *     UpdatableTile#setElevation(int, int, double) tile.setElevation(i, j,
+     *     UpdatableTile#setElevation(int, int, double) tile.setElevation(kLat, kLon,
      *     elevation)} must be the elevation corresponding to the latitude
-     *     {@code minLatitude + i * latitudeStep} and longitude {@code
-     *     minLongitude + j * longitudeStep}, where {@code minLatitude},
+     *     {@code minLatitude + kLat * latitudeStep} and longitude {@code
+     *     minLongitude + kLon * longitudeStep}, where {@code minLatitude},
      *     {@code latitudeStep}, {@code minLongitude} and {@code longitudeStep}
      *     correspond to the parameter of the {@link UpdatableTile#setGeometry(double,
      *     double, double, double, int, int) tile.setGeometry(minLatitude, minLongitude,

core/src/main/java/org/orekit/rugged/raster/UpdatableTile.java

@@ -38,6 +38,16 @@ public interface UpdatableTile {
         throws RuggedException;
 
     /** Set the elevation for one raster element.
+     * <p>
+     * BEWARE! The order of the indices follows geodetic conventions, i.e.
+     * the latitude is given first and longitude afterwards, so the first
+     * index specifies a <em>row</em> index with zero at South and max value
+     * at North, and the second index specifies a <em>column</em> index
+     * with zero at West and max value at East. This is <em>not</em> the
+     * same as some raster conventions (as our row index increases from South
+     * to North) and this is also not the same as Cartesian coordinates as
+     * our ordinate index appears before our abscissa index).
+     * </p>
      * @param latitudeIndex index of latitude (row index)
      * @param longitudeIndex index of longitude (column index)
      * @param elevation elevation (m)