--- android/TrainInfoService/src/dk/thoerup/traininfoservice/StationDAO.java	2010/05/19 07:40:00	737
+++ android/TrainInfoService/src/dk/thoerup/traininfoservice/StationDAO.java	2010/05/19 12:56:10	741
@@ -101,12 +101,19 @@
 		return result;
 	}
 	 
-	//the "hack" with max 2.5 degrees latitude and longitude is only valid since we only service danish trains
+	//the "hack" with max 1.5 degrees latitude and 2.5 degrees longitude is only valid since we only service danish trains
+	// in denmark 1.5dg latitude ~ 165km, 2.5dg longitude ~ 155km
+	
+	// the ultra fast method  (and only slightly inaccurate as long as we only cover a limited geographically area)
+	// is using an aproximation of the length of 1 latitude degree and 1 longitude degree and just use pythagoras to 
+	// calculate the distance:
+    //     sqrt( power(abs(latitude-?)*111320, 2) + power(abs(longitude-?)*63000,2) )::int as calcdist 
+	
 	public List<StationBean> getByLocation(double latitude, double longitude) throws SQLException {
 		String SQL = "SELECT id,name,latitude,longitude,stationcode_fjrn,stationcode_stog, stationcode_metro, address," + 
 					 "       earth_distance( earth_coord, ll_to_earth(?,?))::int AS calcdist " + 
 					 "FROM trainstations " +
-					 "WHERE enabled = true AND abs(latitude-?)<2.5 AND abs (longitude-?)<2.5 " +
+					 "WHERE enabled = true AND abs(latitude-?)<1.5 AND abs(longitude-?)<2.5 " +
 					 "ORDER BY calcdist ASC " + 
 					 "LIMIT 4 ";
 		List<StationBean> result;