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README.md

java code for geohashes

An implementation of Geohashes in pure Java. The produced hashes, when using character precision (multiples of 5 bits) are compatible to the reference implementation geohash.org.

You can however also encode Geohashes down to the full available precision of a long i.e. 64 bits.

Build status

Getting the library

As of today, new releases are made available via maven Central. Thus you can use the artifacts in various build systems like maven, ivy, gradle, sbt and many more.

Find the current versions here:

http://search.maven.org/#search|ga|1|g%3A%22ch.hsr%22%20AND%20a%3A%22geohash%22

Building/Testing the code

The geohash-java code can be built using Apache Maven.

Maven targets are the usual suspects.

- clean    
- compile
- test
- package   # pack a versioned jar containing the compiled class files

Digits and precision in km

geohash length lat bits lng bits lat error lng error ~km error
1 2 3 ±23 ±23 ±2500
2 5 5 ±2.8 ±5.6 ±630
3 7 8 ±0.70 ±0.70 ±78
4 10 10 ±0.087 ±0.18 ±20
5 12 13 ±0.022 ±0.022 ±2.4
6 15 15 ±0.0027 ±0.0055 ±0.61
7 17 18 ±0.00068 ±0.00068 ±0.076
8 20 20 ±0.000085 ±0.00017 ±0.019

Compatibility

This branch ditches 1.6 compatibility. If you need that look at the release-1.0 branch and artifacts in maven central. I will backport important bugfixes to the release-1.0 branch.

TODO

Current development involves getting the following things to run:

  • a method to find the n closest hashes to any given point.
  • refactor tests, might want to add a dependency on hamcrest and provide some custom matchers for fun and profit.

Last important changes

Version 1.4.0

This version adds support for BoundingBoxes to go over the 180 meridian, which enables searching and querying by covering them with Geohashes. This was a much requested feature that made it into the library now, but depending on how you construct BoundingBoxes and how you use the library, this is a breaking change.

In this version you need to provide latitude and longitude to BoundingBox in a specific order for this wo work:

new BoundingBox(south, north, west, east);

This breaking change enables creating bounding boxes that go over the 180 meridian which can then be used in coverage queries.

This version also changes the toString() implementation of GeoHash to always include leading zeroes, so if your code actually relies on that, you will also need to change things downstream that potentially use a prefix query for matching points in a GeoHashs BoundingBox.

Fo now, we will continue to backport other fixes to the 1.3.x branch, so you can keep on using that version as well.

Version 1.3.0

This version switches the license over to Apache Software License 2.0

Version 1.1.0

Important fix 398d048b66e8cff1e5df8aa1a4bdc4c37ca70070 ord() would return negative longs, which is plain wrong.

Thanks to Graham Dennis and aborochoff for pointing it out.

Also: Raise source level to 1.7.

Version 1.0.13

Merge this fix https://github.com/0mok/geohash-java/commit/12550a392ea974cf75c81fce2bd21fe1535715a1 It causes compareTo() of geohashes to behave similarly as comaring their base32 encoded strings

Version 1.0.12

toBase32() now throws an exception if the hash precision is not a multiple of 5.

Version 1.0.11

  • Added a static method to obtain a geohash string in one call. Thanks to Andy Chosak.

Version 1.0.10

Finally realeased to maven central.

Version 1.0.9

  • Added method getCharacterPrecision() to GeoHash class

Version 1.0.8

  • Changed the code in VincentyGeodesy not to stumble over the fact that NaN == NaN will always return false

Version 1.0.6

  • Added a small fix that keeps VincentyGeodesy#moveInDirection() from returning wrong values when moving large distances. [submitted by André Kischkel]

Version 1.0.5

  • Added next(), next(step) and prev() methods to Geohash.
  • Added fromBase32() and toBase32() to TwoGeoHashBoundingBox.
  • Cleaned up the entire source tree using clearly defined settings.

Version 1.0.4

  • Added/fixed the methods toBinaryString() and Geohash.fromBinaryString() that can encode and decode a geohash into a simple String of 0s and 1s.
  • Also added test code for those methods.

Version 1.0.3

  • Classes containing data are now Serializable.

Version 1.0.2

  • Merged Kevins [ktcorby] code that yields all the geohashes in a bounding box, at a given resolution.
  • Merged Chris' [cchandler] code to encode and decode geohashes from a binary string.

Version 1.0.1

  • Fixed issue #2 from Github:

    • Neighbouring hashes can be calculated by using the getAdjacent() method, which yields a hashes 8 neighbors.
    • northern, eastern, western and southern neighbours can be determined using the respective methods.
  • Fixed issue #1 from Github:

    • A bug caused different hashes to be yielded sometimes.

License

This code has been placed under the Apache License 2.0. See the LICENSE file for more information. Please contribute improvements and bug fixes back via github.

About

Implementation of GeoHashes in java. We try to be/stay compliant to the spec, as far as possible.

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