Use 1/9 Arcsecond Elevation Data (#155)

core/src/main/java/com/graphhopper/reader/dem/AbstractTiffElevationProvider.java

@@ -40,11 +40,11 @@ public abstract class AbstractTiffElevationProvider extends TileBasedElevationPr
     final int HEIGHT;
 
     // Degrees of latitude covered by this tile
-    final int LAT_DEGREE;
+    final double LAT_DEGREE;
     // Degrees of longitude covered by this tile
-    final int LON_DEGREE;
+    final double LON_DEGREE;
 
-    public AbstractTiffElevationProvider(String baseUrl, String cacheDir, String downloaderName, int width, int height, int latDegree, int lonDegree) {
+    public AbstractTiffElevationProvider(String baseUrl, String cacheDir, String downloaderName, int width, int height, double latDegree, double lonDegree) {
         super(cacheDir);
         this.baseUrl = baseUrl;
         this.downloader = new Downloader(downloaderName).setTimeout(10000);
@@ -74,12 +74,12 @@ public void release() {
     /**
      * The smallest lat that is still in the HeightTile
      */
-    abstract int getMinLatForTile(double lat);
+    abstract double getMinLatForTile(double lat);
 
     /**
      * The smallest lon that is still in the HeightTile
      */
-    abstract int getMinLonForTile(double lon);
+    abstract double getMinLonForTile(double lon);
 
     /**
      * Specify the name of the file after downloading
@@ -110,8 +110,8 @@ public double getEle(double lat, double lon) {
             if (!cacheDir.exists())
                 cacheDir.mkdirs();
 
-            int minLat = getMinLatForTile(lat);
-            int minLon = getMinLonForTile(lon);
+            double minLat = getMinLatForTile(lat);
+            double minLon = getMinLonForTile(lon);
             // less restrictive against boundary checking
             demProvider = new HeightTile(minLat, minLon, WIDTH, HEIGHT, LON_DEGREE * precision, LON_DEGREE, LAT_DEGREE);
             demProvider.setInterpolate(interpolate);

core/src/main/java/com/graphhopper/reader/dem/CGIARProvider.java

@@ -118,9 +118,9 @@ Raster generateRasterFromFile(File file, String tifName) {
 
     int down(double val) {
         // 'rounding' to closest 5
-        int intVal = (int) (val / LAT_DEGREE) * LAT_DEGREE;
+        int intVal = (int) ((int) (val / LAT_DEGREE) * LAT_DEGREE);
         if (!(val >= 0 || intVal - val < invPrecision))
-            intVal = intVal - LAT_DEGREE;
+            intVal = (int) (intVal - LAT_DEGREE);
 
         return intVal;
     }
@@ -151,12 +151,12 @@ protected String getFileName(double lat, double lon) {
     }
 
     @Override
-    int getMinLatForTile(double lat) {
+    double getMinLatForTile(double lat) {
         return down(lat);
     }
 
     @Override
-    int getMinLonForTile(double lon) {
+    double getMinLonForTile(double lon) {
         return down(lon);
     }
 

core/src/main/java/com/graphhopper/reader/dem/GMTEDProvider.java

@@ -154,15 +154,15 @@ Raster generateRasterFromFile(File file, String tifName) {
         }
     }
 
-    int getMinLatForTile(double lat) {
+    double getMinLatForTile(double lat) {
         return (int) (Math.floor((90 + lat) / LAT_DEGREE) * LAT_DEGREE) - 90;
     }
 
-    int getMinLonForTile(double lon) {
+    double getMinLonForTile(double lon) {
         return (int) (Math.floor((180 + lon) / LON_DEGREE) * LON_DEGREE) - 180;
     }
 
-    private String getLonString(int lonInt) {
+    private String getLonString(double lonInt) {
         lonInt = Math.abs(lonInt);
         String lonString = lonInt < 100 ? "0" : "";
         if (lonInt < 10)
@@ -171,7 +171,7 @@ private String getLonString(int lonInt) {
         return lonString;
     }
 
-    private String getLatString(int latInt) {
+    private String getLatString(double latInt) {
         latInt = Math.abs(latInt);
         String latString = latInt < 10 ? "0" : "";
         latString += latInt;
@@ -184,14 +184,14 @@ boolean isOutsideSupportedArea(double lat, double lon) {
     }
 
     String getFileName(double lat, double lon) {
-        int lonInt = getMinLonForTile(lon);
-        int latInt = getMinLatForTile(lat);
+        double lonInt = getMinLonForTile(lon);
+        double latInt = getMinLatForTile(lat);
         return toLowerCase(getLatString(latInt) + getNorthString(latInt) + getLonString(lonInt) + getEastString(lonInt) + FILE_NAME_END);
     }
 
     String getDownloadURL(double lat, double lon) {
-        int lonInt = getMinLonForTile(lon);
-        int latInt = getMinLatForTile(lat);
+        double lonInt = getMinLonForTile(lon);
+        double latInt = getMinLatForTile(lat);
         String east = getEastString(lonInt);
         String lonString = getLonString(lonInt);
         return baseUrl + "/" + east + lonString + "/" + getLatString(latInt) + getNorthString(latInt) + lonString + east + FILE_NAME_END + ".tif";
@@ -202,14 +202,14 @@ String getFileNameOfLocalFile(double lat, double lon) {
         return getFileName(lat, lon) + ".tif";
     }
 
-    private String getNorthString(int lat) {
+    private String getNorthString(double lat) {
         if (lat < 0) {
             return "S";
         }
         return "N";
     }
 
-    private String getEastString(int lon) {
+    private String getEastString(double lon) {
         if (lon < 0) {
             return "W";
         }

core/src/main/java/com/graphhopper/reader/dem/HeightTile.java

@@ -33,12 +33,12 @@
  * @author Peter Karich
  */
 public class HeightTile {
-    private final int minLat;
-    private final int minLon;
+    private final double minLat;
+    private final double minLon;
     private final int width;
     private final int height;
-    private final int horizontalDegree;
-    private final int verticalDegree;
+    private final double horizontalDegree;
+    private final double verticalDegree;
     private final double lowerBound;
     private final double lonHigherBound;
     private final double latHigherBound;
@@ -47,7 +47,7 @@ public class HeightTile {
     private final double MIN_ELEVATION_METERS = -12_000;
     private final double MAX_ELEVATION_METERS = 9_000;
 
-    public HeightTile(int minLat, int minLon, int width, int height, double precision, int horizontalDegree, int verticalDegree) {
+    public HeightTile(double minLat, double minLon, int width, int height, double precision, double horizontalDegree, double verticalDegree) {
         this.minLat = minLat;
         this.minLon = minLon;
         this.width = width;

core/src/main/java/com/graphhopper/reader/dem/MultiSourceElevationProvider.java

@@ -32,6 +32,16 @@ public class MultiSourceElevationProvider extends TileBasedElevationProvider {
     // The fallback provider that provides elevation data globally
     private final TileBasedElevationProvider fallback;
 
+    // While we may have precise elevation data for certain coordinates lying
+    // on the edges of a defined supported area, a TileElevationProvider's
+    // implementation could result in a situation where it requests elevation
+    // data from an adjacent tile instead, in consistency with its naming
+    // convention.
+    //
+    // Removing a small buffer region from the supported area eliminates this
+    // literal edge case.
+    private final double DEGREES_BUFFER = 0.001;
+
     public MultiSourceElevationProvider(
             TileBasedElevationProvider primary,
             TileBasedElevationProvider fallback) {
@@ -50,7 +60,8 @@ public MultiSourceElevationProvider(String cacheDir) {
 
     @Override
     public double getEle(double lat, double lon) {
-        if (lat > 37 && lat < 38 && lon > -123 && lon < -122)
+        if (lat > 37.5 + DEGREES_BUFFER && lat < 38.25 - DEGREES_BUFFER &&
+                lon > -122.75 + DEGREES_BUFFER && lon < -122 - DEGREES_BUFFER)
             return primary.getEle(lat, lon);
         return fallback.getEle(lat, lon);
     }

core/src/main/java/com/graphhopper/reader/dem/USGSProvider.java

@@ -13,15 +13,13 @@
 
 public class USGSProvider extends AbstractTiffElevationProvider {
 
-    String filename = "n38w123";
-
     public USGSProvider(String cacheDir) {
-        this("", cacheDir, "", 10812, 10812, 1, 1);
+        this("", cacheDir, "", 8112, 8112, 0.25, 0.25);
     }
 
     public USGSProvider(String baseUrl, String cacheDir,
-            String downloaderName, int width, int height, int latDegree,
-            int lonDegree) {
+            String downloaderName, int width, int height, double latDegree,
+            double lonDegree) {
         super(baseUrl, cacheDir, downloaderName, width, height, latDegree,
                 lonDegree);
     }
@@ -32,34 +30,54 @@ public static void main(String[] args) {
         // Market Street ~-5ft to 260ft in prod.
         System.out.println("Elevation: " + elevationProvider.getEle(37.7903317182555, -122.39999824547087) + "m");
         System.out.println("Elevation: " + elevationProvider.getEle(37.79112431722635, -122.39901032204128) + "m");
-
-        // Mount Davidson, expected: ~283m
-        System.out.println("Elevation: " + elevationProvider.getEle(37.738259, -122.45463) + "m");
     }
 
     @Override
     boolean isOutsideSupportedArea(double lat, double lon) {
-        return lat < 37 || lat > 38 || lon < -123 || lon > -122;
+        return lat < 37.5 || lat > 38.25 || lon < -122.75 || lon > -122;
     }
 
     @Override
-    int getMinLatForTile(double lat) {
-        return 37;
+    double getMinLatForTile(double lat) {
+        return Math.floor(lat * 4) / 4;
     }
 
     @Override
-    int getMinLonForTile(double lon) {
-        return -123;
+    double getMinLonForTile(double lon) {
+        return Math.floor(lon * 4) / 4;
     }
 
     @Override
     String getFileNameOfLocalFile(double lat, double lon) {
-        return filename + ".tif";
+        return getFileName(lat, lon) + ".tif";
     }
 
+    /**
+     * The USGS National Elevation Dataset (NED)'s 1/9th arc-second DEM offering
+     * categorizes individual 0.25x0.25 degree tiles using the northwestern
+     * corner of each tile. For example, <i>ned19_n37x75_w122x50</i> means that
+     * the corners of the tile are (starting from the northwestern corner and
+     * moving clockwise):
+     * <ul>
+     *   <li>37.75, -122.50</li>
+     *   <li>37.75, -122.25</li>
+     *   <li>37.50, -122.25</li>
+     *   <li>37.50, -122.50</li>
+     * </ul>
+     * @param lat latitude in degrees, ranges from [-90.0, 90.0]
+     * @param lon longitude in degrees, ranges from [-180.0, 180.0]
+     * @return Filename in format ned19_{n,s}AAxAA_{e,w}BBBxBB;
+     * AAxAA being latitude in degrees and BBBxBB being longitude in degrees
+     */
     @Override
     String getFileName(double lat, double lon) {
-        return filename;
+        double latAdjusted = Math.abs(Math.ceil(lat * 4) / 4);
+        int latDecimals = (int)(latAdjusted * 100) % 100;
+
+        double lonAdjusted = Math.abs(getMinLonForTile(lon));
+        int lonDecimals = (int)(lonAdjusted * 100) % 100;
+
+        return String.format("ned19_n%dx%02d_w%dx%02d", (int) latAdjusted, latDecimals, (int) lonAdjusted, lonDecimals);
     }
 
     @Override
@@ -79,8 +97,8 @@ public double getEle(double lat, double lon) {
         if (demProvider == null) {
             if (!cacheDir.exists()) cacheDir.mkdirs();
 
-            int minLat = getMinLatForTile(lat);
-            int minLon = getMinLonForTile(lon);
+            double minLat = getMinLatForTile(lat);
+            double minLon = getMinLonForTile(lon);
             // less restrictive against boundary checking
             demProvider = new HeightTile(minLat, minLon, WIDTH, HEIGHT,
                     LON_DEGREE * precision, LON_DEGREE, LAT_DEGREE);
@@ -101,11 +119,9 @@ public double getEle(double lat, double lon) {
                         new File(getFileNameOfLocalFile(lat, lon)).getName());
 
                 // short == 2 bytes
-                heights.create(2 * WIDTH * HEIGHT);
-
+                heights.create(2L * WIDTH * HEIGHT);
                 Raster raster = generateRasterFromFile(file, name + ".tif");
                 super.fillDataAccessWithElevationData(raster, heights, WIDTH);
-
             } // loadExisting
         }
 
@@ -128,4 +144,6 @@ Raster generateRasterFromFile(File file, String tifName) {
                 close(ss);
         }
     }
+
+    public String toString() { return "usgs"; }
 }

core/src/test/java/com/graphhopper/reader/dem/USGSProviderTest.java

@@ -0,0 +1,40 @@
+package com.graphhopper.reader.dem;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+class USGSProviderTest {
+
+    USGSProvider provider = new USGSProvider("");
+
+    @Test
+    public void testMinLat() {
+        assertEquals(37.75, provider.getMinLatForTile(37.76));
+        assertEquals(37.75, provider.getMinLatForTile(37.75));
+        assertEquals(37.5, provider.getMinLatForTile(37.74));
+
+        assertEquals(-38, provider.getMinLatForTile(-37.76));
+        assertEquals(-37.75, provider.getMinLatForTile(-37.75));
+        assertEquals(-37.75, provider.getMinLatForTile(-37.74));
+    }
+
+    @Test
+    public void testMinLon() {
+        assertEquals(122.25, provider.getMinLonForTile(122.26));
+        assertEquals(122.25, provider.getMinLonForTile(122.25));
+        assertEquals(122, provider.getMinLonForTile(122.24));
+
+        assertEquals(-122.5, provider.getMinLonForTile(-122.26));
+        assertEquals(-122.25, provider.getMinLonForTile(-122.25));
+        assertEquals(-122.25, provider.getMinLonForTile(-122.24));
+    }
+
+    @Test
+    public void testFilename() {
+        assertEquals("ned19_n38x00_w122x50",
+                provider.getFileName(38, -122.5));
+        assertEquals("ned19_n38x00_w122x50",
+                provider.getFileName(37.76, -122.26));
+    }
+}