Changeset 8696 in josm for trunk/src/org

Timestamp:

2015-08-27T21:19:44+02:00 (9 years ago)

Author:

wiktorn

Message:

Glue WMS zoom levels to TMS zoom levels.

Based on WMTS well known scale set (in OGC spec: ​http://www.opengeospatial.org/standards/wmts) GoogleMapsCompatibile
implement same zoom levels for WMS in JOSM. This change makes WMS zoom levels corresponding (identical?) to TMS zoom
levels and independent of current projection (as it was till now).

Addresses: #11808

File:

• trunk/src/org/openstreetmap/josm/data/imagery/TemplatedWMSTileSource.java (modified) (3 diffs)

trunk/src/org/openstreetmap/josm/data/imagery/TemplatedWMSTileSource.java

@@ -62 +62 @@
     };
 
+    /*
+     * Constant taken from OGC WMTS Implementation Specification (http://www.opengeospatial.org/standards/wmts)
+     * From table E.4 - Definition of Well-known scale set GoogleMapsCompatibile
+     *
+     *  As higher zoom levels have denominator divided by 2, we keep only zoom level 1 in the code
+     */
+    private static final float SCALE_DENOMINATOR_ZOOM_LEVEL_1 = 559082264.0287178f;
+
     /**
      * Creates a tile source based on imagery info
@@ -72 +80 @@
         initProjection();
         // FIXME: remove in September 2015, when ImageryPreferenceEntry.tileSize will be initialized to -1 instead to 256
-        // need to leave it as it is to keep compatiblity between tested and latest JOSM versions
+        // need to leave it as it is to keep compatibility between tested and latest JOSM versions
         tileSize = WMSLayer.PROP_IMAGE_SIZE.get();
     }
@@ -94 +102 @@
 
         LatLon bottomRight = new LatLon(worldBounds.getMinLat(), worldBounds.getMaxLon());
+
+        // use 256 as "tile size" to keep the scale in line with default tiles in Mercator projection
+        double crsScale = 256 * 0.28e-03 / proj.getMetersPerUnit();
         tileXMax = new int[getMaxZoom() + 1];
         tileYMax = new int[getMaxZoom() + 1];
-        degreesPerTile = new double[getMaxZoom() +1];
+        degreesPerTile = new double[getMaxZoom() + 1];
+
         for (int zoom = getMinZoom(); zoom <= getMaxZoom(); zoom++) {
             TileXY maxTileIndex = latLonToTileXY(bottomRight.toCoordinate(), zoom);
             tileXMax[zoom] = maxTileIndex.getXIndex();
             tileYMax[zoom] = maxTileIndex.getYIndex();
-            int tilesPerZoom = (int) Math.pow(2d, zoom - 1);
-            degreesPerTile[zoom] = Math.max(
-                    Math.abs(max.getY() - min.getY()) / tilesPerZoom,
-                    Math.abs(max.getX() - min.getX()) / tilesPerZoom
-                    );
-
+            // use well known scale set "GoogleCompatibile" from OGC WMTS spec to calculate number of tiles per zoom level
+            // this makes the zoom levels "glued" to standard TMS zoom levels
+            degreesPerTile[zoom] = (SCALE_DENOMINATOR_ZOOM_LEVEL_1 / Math.pow(2, zoom - 1)) * crsScale;
         }