Changeset 29877 in osm for applications/editors/josm/plugins/ElevationProfile/src/org/openstreetmap

Timestamp:

2013-08-25T20:50:29+02:00 (11 years ago)

Author:

oliverw

Message:

Check for HGT buffer size and data voids.

Location:

applications/editors/josm/plugins/ElevationProfile/src/org/openstreetmap/josm/plugins/elevation

Files:

• HgtReader.java (modified) (4 diffs)
• tests/HgtReaderTest.java (modified) (1 diff)

applications/editors/josm/plugins/ElevationProfile/src/org/openstreetmap/josm/plugins/elevation/HgtReader.java

@@ -20 +20 @@
  */
 public class HgtReader {
+    private static final int SECONDS_PER_MINUTE = 60;
+
     public static final String HGT_EXT = ".hgt";
     
@@ -25 +27 @@
     public static final int HGT_RES = 3; // resolution in arc seconds
     public static final int HGT_ROW_LENGTH = 1201; // number of elevation values per line
+    public static final int HGT_VOID = -32768; // magic number which indicates 'void data' in HGT file
     
     private HashMap<String, ShortBuffer> cache = new HashMap<String, ShortBuffer>(); 
@@ -38 +41 @@
                 // but is not there'
                 cache.put(file, null);
-                 // Try all other resource directories
+                 // Try all resource directories
                 for (String location : Main.pref.getAllPossiblePreferenceDirs()) {                  
                         String fullPath = new File(location + File.separator + "elevation", file).getPath();
                                   
-                        System.out.println("Search in " + location);
+                        System.out.println(fullPath);
                         File f = new File(fullPath);
                         if (f.exists()) {
@@ -108 +111 @@
         
         // see http://gis.stackexchange.com/questions/43743/how-to-extract-elevation-from-hgt-file
-        double fLat = frac(coor.lat()) * 60;
-        double fLon = frac(coor.lon()) * 60;
+        double fLat = frac(coor.lat()) * SECONDS_PER_MINUTE;
+        double fLon = frac(coor.lon()) * SECONDS_PER_MINUTE;
         
-        
-        int row = (int)Math.round(fLat * 60 / HGT_RES); 
-        int col = (int)Math.round(fLon * 60 / HGT_RES);
+        // compute offset within HGT file
+        int row = (int)Math.round(fLat * SECONDS_PER_MINUTE / HGT_RES); 
+        int col = (int)Math.round(fLon * SECONDS_PER_MINUTE / HGT_RES);
         
         row = HGT_ROW_LENGTH - row;
         int cell = (HGT_ROW_LENGTH*  (row - 1)) + col;
 
-        return sb.get(cell);
+        // valid position in buffer?
+        if (cell < sb.limit()) {
+            short ele = sb.get(cell);
+            // check for data voids 
+            if (ele == HGT_VOID) {
+                return Double.NaN;
+            } else {
+                return ele;
+            }
+        } else {
+            return Double.NaN;
+        }
     }
     

applications/editors/josm/plugins/ElevationProfile/src/org/openstreetmap/josm/plugins/elevation/tests/HgtReaderTest.java

@@ -38 +38 @@
         double d = hr.getElevationFromHgt(l);
         System.out.println(d);
-        assert(!Double.isNaN(d));
+        assertFalse("Data missing or void for coor " + l, Double.isNaN(d));
+        
         assertEquals((int)d, expHeight);
     }