Java tool for compress and decompress list of points by bing point compression algorithm Point Compression Algorithm
When the number of points (latitude and longitude pairs) becomes too large, the length of the URL request may exceed limits imposed by clients, proxies, or the server. To reduce the size of the request or when you cannot use the HTTP POST method, you can implement the compression algorithm described below to get a compressed string that you can use instead of the lengthy points list. The points parameter in the Elevation API URLs supports these compressed strings and automatically returns uncompressed elevation data. There is no need for a decompression algorithm. This algorithm is best for 400 points or less. If you are requesting elevation data for more than 400 points, make an HTTP POST request. The following example shows the difference in size between a list of points and the equivalent compressed string
Note: Due to the algorithm lat/lon rounding the close enough points (distance ~ 0.009076 km) could be dropped. This can be influenced through changing of the Multiplier constant (there is a direct correlation between the how big the multiplier is and how accurate is the rounding) The obvious drawback is: The bigger the Multiplier - the bigger the size of the compressed points final payload, but it grows slowly and linearly.
Original Values:
points=35.894309002906084,-110.72522000409663,35.893930979073048,-110.72577999904752,35.893744984641671,-110.72606003843248,35.893366960808635,-110.72661500424147
Equivalent Compressed Value:
points=vx1vilihnM6hR7mEl2Q
In order to use, simply add these lines to your project's pom.xml
<dependency>
<groupId>org.meteogroup</groupId>
<artifactId>point-compression</artifactId>
<version>1.0</version>
</dependency> //String locations = ...
List<Point> points = new PointDecompression().decompressPoints(locations); //List<Point> points = ...
String locations = new PointCompression().compressAsString(points);