trendingtechnology / georange

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).

Heavily influenced by GeoFlutterFire

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();