A package that helps with encoding and decoding of geohashes

georange

georange is a package that helps with encoding geohashes, decoding geohashes,calculating distance between 2 points and generating latitudinal and longitudinal ranges as geohashes to help with the querying of databases (tested on firestore only).

getting started

you should ensure that you add georange as a dependency in your flutter project.

dependencies:
  georange: <latest-version>

you should then run flutter packages get

example

there is a detailed example project in the example folder.

initialize

import georange to your dart file and initialize

import 'package:georange/georange.dart';
georange georange = georange();

encode latlng

this method encodes the latitude and longitude

var encoded = georange.encode(-1.2862368,36.8195783);
print(encoded);

prints kzf0tvg5n

decode geohash

decode a [geohash] into a pair of latitude and longitude.

point decoded = georange.decode("kzf0tvg5n");
print(decoded);

prints
-1.2862372398376465
36.819584369659424

generate range

  range range = georange.geohashrange(-1.2921, 36.8219, distance: 10);
  print(range.lower);
  print(range.upper);

prints
kzf05k6hh
kzf30mptu

calculate distance between 2 points

  point point1 = point(latitude: -4.0435, longitude: 39.6682); //mombasa
  point point2 = point(latitude: -1.2921, longitude: 36.8219); // nairobi

  var distance = georange.distance(point1, point2);
  print(distance);

prints
439.716 distance in kilometres

usage with firestore

1. add a document to firestore with a geohash field or a different name

  final firebasefirestore _db;
  ...
  string myhash = georange.encode(-1.2862368,36.8195783);
  await _db.collection("locations").add({
    "geohash":myhash,
  })
  ...

2. query firestore (runs like a normal firestore query)

final firebasefirestore _db;

georange georange = georange();

range range = georange.geohashrange(currentlocation.latitude, currentlocation.longitude, distance:10);

querysnapshot snapshot = await _db
 .collection("locations")
 .where("geohash", isgreaterthanorequalto: range.lower)
 .where("geohash", islessthanorequalto: range.upper)
 .limit(10)
 .get();