Geohashing is turning latitude and longitude pairs into a single string or number. This library implements the oldest popular geohashing algorithm, invented in 2008 by Gustavo Niemeyer.

Some base code was translated from the MIT-licensed latlon-geohash by Chris Veness, the author of the Movable Type blog. Integer geohash code is inspired by node-geohash by Ning Sun, also MIT-licensed.

This library is built to replace geohash, dart_geohash, proximity_hash, and others.

Unlike other packages, this one is actively used in a popular project, is written in pure Dart, made with performance in mind, and does not depend on anything.

Pan and zoom the map in the interactive demo!

Usage

Import either the string or the integer part of the library. Either contains a single constant named geohash with all the methods:

import 'package:fast_geohash/fast_geohash_str.dart';

void main() {
  // Encode a latitude and a longitude into a string.
  print(geohash.encode(78.220864, 15.643212, 7)); // "umghgzx"
  
  // Decode a string into a coordinate record.
  final ll = geohash.decode("6q2cgc");
  print("${ll.lat}, ${ll.lon}"); // "-9.52789306640625, -77.5250244140625"
  
  // Find all geohashes covering a circle with the given centre and radius in meters.
  final hashes = geohash.forCircle(-1.279488, 36.816839, 200, 7);
  print(hashes); // [kzf0tz1, kzf0tz0, kzf0txp, kzf0tz4]
}

Integer geohashes might be faster to work with, since they are easier to index, and they fit into 64 bits. Note that the top bit is always set to record the geohash precision, and that a character in the string geohash is equivalent to 5 bits.

import 'package:fast_geohash/fast_geohash_int.dart';

void main() {
  print(geohash.encode(78.220864, 15.643212,  7).toRadixString(2)); // 11101010
  print(geohash.encode(78.220864, 15.643212, 12).toRadixString(2)); // 1110101001101

  final hashes = geohash.forBounds(45.818, 5.9559, 47.8084, 10.4921, 15);
  print(hashes.map((h) => h.toRadixString(8)));
  // (164022, 164023, 164026, 164027, 164020, 164021, 164024, 164025)
}

See Also

For other hashing algorithms, see:

Libraries

fast_geohash_int
fast_geohash_str