initial commit of BRouter Version 0.98

brouter-map-creator/src/main/java/btools/mapcreator/SrtmData.java

@@ -0,0 +1,174 @@
+/**
+ * This is a wrapper for a 5*5 degree srtm file in ascii/zip-format
+ *
+ * - filter out unused nodes according to the way file
+ * - enhance with SRTM elevation data
+ * - split further in smaller (5*5 degree) tiles
+ *
+ * @author ab
+ */
+package btools.mapcreator;
+
+import java.io.BufferedReader;
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.util.zip.ZipEntry;
+import java.util.zip.ZipInputStream;
+
+
+public class SrtmData
+{
+  public int ncols;
+  public int nrows;
+  public double xllcorner;
+  public double yllcorner;
+  public double cellsize;
+  public int nodata_value;
+  public short[] eval_array;
+
+  private double minlon;
+  private double maxlon;
+  private double minlat;
+  private double maxlat;
+
+  public void init()
+  {
+    minlon = xllcorner;
+    maxlon = minlon + cellsize*ncols;
+    minlat = yllcorner;
+    maxlat = minlat + cellsize*nrows;
+  }
+
+  private boolean missingData = false;
+
+  public short getElevation( int ilon, int ilat )
+  {
+    double lon = ilon / 1000000. - 180.;
+    double lat = ilat / 1000000. - 90.;
+
+    double dcol = (lon - minlon)/cellsize -0.5;
+    double drow = (lat - minlat)/cellsize -0.5;
+    int row = (int)drow;
+    int col = (int)dcol;
+    if ( col < 0 ) col = 0;
+    if ( col >= ncols-1 ) col = ncols - 2;
+    if ( row < 0 ) row = 0;
+    if ( row >= nrows-1 ) row = nrows - 2;
+    double wrow = drow-row;
+    double wcol = dcol-col;
+    missingData = false;
+    double eval = (1.-wrow)*(1.-wcol)*get(row  ,col  )
+             + (   wrow)*(1.-wcol)*get(row+1,col  )
+             + (1.-wrow)*(   wcol)*get(row  ,col+1)
+             + (   wrow)*(   wcol)*get(row+1,col+1);
+    return missingData ? Short.MIN_VALUE : (short)(eval);
+  }
+
+  private short get( int r, int c )
+  {
+    short e = eval_array[r*ncols + c ];
+    if ( e == Short.MIN_VALUE ) missingData = true;
+    return e;
+  }
+
+  public SrtmData( File file ) throws Exception
+  {
+    ZipInputStream zis = new ZipInputStream( new FileInputStream( file ) );
+    try
+    {
+      for(;;)
+      {
+        ZipEntry ze = zis.getNextEntry();
+        if ( ze.getName().endsWith( ".asc" ) )
+        {
+          readFromStream( zis );
+
+/*        // test
+        int[] ca = new int[]{ 50477121, 8051915, // 181
+                              50477742, 8047408, // 154
+                              50477189, 8047308, // 159
+                                  };
+        for( int i=0; i<ca.length; i+=2 )
+        {
+           int lat=ca[i] + 90000000;
+           int lon=ca[i+1] + 180000000;
+            System.err.println( "lat=" + lat + " lon=" + lon + " elev=" + getElevation( lon, lat )/4. );
+        }
+        // end test
+*/
+          return;
+        }
+      }
+    }
+    finally
+    {
+      zis.close();
+    }
+  }
+
+
+  public void readFromStream( InputStream is ) throws Exception
+  {
+    BufferedReader br = new BufferedReader(new InputStreamReader(is));
+    int linenr = 0;
+    for(;;)
+    {
+      linenr++;
+      if ( linenr <= 6 )
+      {
+        String line = br.readLine();
+        if      ( linenr == 1 ) ncols = Integer.parseInt( line.substring(14) );
+        else if ( linenr == 2 ) nrows = Integer.parseInt( line.substring(14) );
+        else if ( linenr == 3 ) xllcorner = Double.parseDouble( line.substring(14) );
+        else if ( linenr == 4 ) yllcorner = Double.parseDouble( line.substring(14) );
+        else if ( linenr == 5 ) cellsize = Double.parseDouble( line.substring(14) );
+        else if ( linenr == 6 )
+        {
+          nodata_value = Integer.parseInt( line.substring(14) );
+          eval_array = new short[ncols * nrows];
+        }
+      }
+      else
+      {
+        int row = 0;
+        int col = 0;
+        int n = 0;
+        boolean negative = false;
+        for(;;)
+        {
+          int c = br.read();
+          if ( c < 0 ) break;
+          if ( c == ' ' )
+          {
+            if ( negative ) n = -n;
+            short val = n == nodata_value ? Short.MIN_VALUE : (short)(n*4);
+            if ( val < -1000 ) val = Short.MIN_VALUE;
+
+            eval_array[ (nrows-1-row)*ncols + col ] = val;
+            if (++col == ncols )
+            {
+              col = 0;
+              ++row;
+            }
+            n = 0;
+            negative = false;
+          }
+          else if ( c >= '0' && c <= '9' )
+          {
+            n = 10*n + (c-'0');
+          }
+          else if ( c == '-' )
+          {
+            negative = true;
+          }
+        }
+        break;
+      }
+    }
+    init();
+    br.close();
+  }
+
+}