geohash is a hashing technique optimised for combining latitude and longitude pairs.

learn more… | top users | synonyms

2
votes
1answer
35 views

Understanding geohash and its associated rectangles

If I decode geohash sj8101b0858n85202hbh0j I get rectangle defined by min latitude, min longitude, max latitude, max longitude. My understanding is that if I decode first part of any hash (e.g. ...
1
vote
1answer
275 views

Google's S2 library - any alternatives?

Is there any alternative to Google's S2 geometry library? It looks it was updated 4 years back and hardly any documentation. I need a library to divide cities into zones of the area I need. S2 looks ...
2
votes
0answers
60 views

How to use Morton Order(z order curve) in range search?

How to use Morton Order in range search? From the wiki, In the paragraph "Use with one-dimensional data structures for range searching", it says: the range being queried (x = 2, ..., 3, y = 2, ...
0
votes
0answers
30 views

O(1) mapping between base32 geohash box to it’s neighbors

geohash-js demonstrates the calculated matrix for neighbor geohashes as following These matrices demonstrate the formation of the geohash base 32 pattern in both vertical and horizontal orientations. ...
1
vote
1answer
209 views

Generating Heat Maps with GeoHash

I have a long list of GeoHash codes for a certain geographic region. I'm using 6-character precision so for example if the area under study was Earl's Court in London, I would have a few six letter ...
2
votes
1answer
1k views

Fastest strategy for proximity searches in SQL Server 2012

This is my very first question here, so bear with me! I'm implementing a back end for a mobile app which will have to do proximity searches to find nearby POIs (points os interest). I know it's a ...
5
votes
1answer
935 views

What is the precision of a Geohash

I would like to know the precision of a geohash with a given length. If there is a 'simple' formula you can use to calculate it, that would be extra-cool. Wikipedia lists the precision up to 8 ...
8
votes
1answer
1k views

Advantages of R-trees in comparison to geohashes

Geohashes are being widely used in products like: Lucene, mongodb, etc and have become one of the most important technology of present day. Have Geohashes replaced the good old R-trees or do R-trees ...
1
vote
1answer
241 views

Algorithm to find geohashes which satisfy query condition

I have an application where I need to query geohashes by specifying the bounding rectangle. Since geohashes map 2D to 1D is there a method by which I may find the prefixes of all geohashes which ...
4
votes
1answer
221 views

What is the internal format of PostGIS?

PostGIS stores its geometry entities as long strings: SELECT ST_GeomFromText('POINT(32.0 34.0)',4326); st_geomfromtext ---------------------------------------------------- ...
4
votes
2answers
572 views

What methods exist for geohash of polygon?

GeoHash is an excellent method to code the latitude and longitude of a point into a string. It's concise, due to the use of numbers + letters, and the precision can be tuned adding characters at the ...
3
votes
1answer
312 views

Are there trade offs between using a geohash vs using a quadkey as a spatial index?

QuadKey Bing Maps uses a quadkey structure for their tiling scheme. Here is an overview of the concept http://msdn.microsoft.com/en-us/library/bb259689.aspx. GeoHash A geohash seems to be the more ...
0
votes
1answer
102 views

Longest common prefix of geohashed points

I currently use Geohash to index some points and retrieve information faster by providing a geohash prefix for a given point for a given distance.. For example if I get a given point at '1600 ...
2
votes
0answers
696 views

Clustering table on geohash index and geohash ordered table

I wonder if there could be a performance gain to re organize the rows in a table by Geohash and then CLUSTER this table on the Geohash index of the geometries. CREATE TEMPORARY TABLE tmptbl AS SELECT ...
13
votes
3answers
7k views

Would it be possible to use geohash for proximity searches?

I'm looking to optimize point proximity geo searches time. My input is lat,lng point and I'm searching on a precomputed set of locations to n nearest points. I don't care how much time/space the ...