src/tim/prune/function/srtm/Srtm3Source.java

   1 package tim.prune.function.srtm;
   2
   3 import java.io.File;
   4 import java.io.IOException;
   5 import java.io.InputStream;
   6 import java.net.MalformedURLException;
   7 import java.net.URL;
   8
   9 import tim.prune.I18nManager;
  10
  11 public class Srtm3Source extends SrtmSource {
  12         /** URL prefix for all tiles */
  13         private static final String URL_PREFIX = "https://dds.cr.usgs.gov/srtm/version2_1/SRTM3/";
  14         /** Directory names for each continent */
  15         private static final String[] CONTINENTS = {"", "Eurasia", "North_America", "Australia",
  16                                                     "Islands", "South_America", "Africa"};
  17         private byte[] _continents_lookup;
  18
  19
  20         public Srtm3Source()
  21         {
  22                 _continents_lookup = populateContinents();
  23         }
  24
  25         public String getNameKey()
  26         {
  27                 return "function.downloadsrtm." + getName();
  28         }
  29
  30         public String getName()
  31         {
  32                 return "SRTM3_v21";
  33         }
  34
  35         protected String getSourceExtension()
  36         {
  37                 return ".hgt.zip";
  38         }
  39
  40         /**
  41          * Read the dat file and get the contents
  42          * @return byte array containing file contents
  43          */
  44         private static byte[] populateContinents()
  45         {
  46                 InputStream in = null;
  47                 try
  48                 {
  49                         // Need absolute path to dat file
  50                         in = Srtm3Source.class.getResourceAsStream("/tim/prune/function/srtm/srtmtiles.dat");
  51                         if (in != null)
  52                         {
  53                                 byte[] buffer = new byte[in.available()];
  54                                 in.read(buffer);
  55                                 in.close();
  56                                 return buffer;
  57                         }
  58                 }
  59                 catch (IOException e) {
  60                         System.err.println("Exception trying to read srtmtiles.dat : " + e.getMessage());
  61                 }
  62                 finally
  63                 {
  64                         try {
  65                                 in.close();
  66                         }
  67                         catch (Exception e) {} // ignore
  68                 }
  69                 return null;
  70         }
  71
  72         /**
  73          * Get the Url for the given tile
  74          * @param inTile Tile to get
  75          * @return URL
  76          */
  77         private URL buildUrl(SrtmTile inTile)
  78                 throws SrtmSourceException
  79         {
  80
  81                 // Get byte from lookup array
  82                 int idx = (inTile.getLatitude() + 59)*360 + (inTile.getLongitude() + 180);
  83                 int dir;
  84                 try
  85                 {
  86                         dir = _continents_lookup[idx];
  87                 }
  88                 catch (ArrayIndexOutOfBoundsException e)
  89                 {
  90                         throw new SrtmSourceException("Could not find continent for tile "+inTile.getTileName());
  91                 }
  92                 try
  93                 {
  94                         return new URL(URL_PREFIX + CONTINENTS[dir] + "/" + inTile.getTileName() + getSourceExtension());
  95                 }
  96                 catch (MalformedURLException e)
  97                 {
  98                         throw new SrtmSourceException("Could not build URL for tile "+inTile.getTileName());
  99                 }
 100         }
 101
 102         public boolean isReadyToUse()
 103         {
 104                 return true;
 105         }
 106
 107         public boolean downloadTile(SrtmTile inTile)
 108                 throws SrtmSourceException
 109         {
 110                 URL tileUrl = buildUrl(inTile);
 111                 InputStream inStream = getStreamToUrl(tileUrl);
 112                 return readToFile(inStream, getCacheFileName(inTile));
 113         }
 114
 115         public int getRowSize(SrtmTile inTile)
 116         {
 117                 return 1201;
 118         }
 119 }