Geohash is a way to encode latitude and longitude coordinates into a short string, allowing locations to be stored, searched, and analyzed efficiently. The presenter will discuss how geohashing works by subdividing space into grid "buckets" and degrading precision with shorter hashes. He will explain how his company uses geohashing to analyze visitors from different locations and check for duplicates more efficiently than with raw latitude/longitude or large addresses.

1. Geohash
{lat/lon → string}
Python Developer Nepal Meetup #6
March 19, 2015

2. Who am I?
Narayan Kandel
Developer at nLocate (Python/Django)
Previously Java Developer at Deerwalk

3. What I Will Cover
1. Our requirements
2. What is a geohash?
3. How does it work?
4. How we use it?

4. Our Requirement
● Analyze visitor from different location
○ different data
1. business data
2. user generated log
● Duplication Check

5. What is Geohashing
Simple way to encode lat/lng into a string
Compact string encoding of geographic coordinate with
arbitrary precision
Kathmandu - tuut, Chitwan - tuuj
Invented by Gustavo Niemeyer for geohash.org
Available in public domain http://en.wikipedia.org/wiki/geohash/

6. Why do we need it when we have lat/lon
Big address of venue
ABC road
Lalitpur Sub-Municipality -12, Kupondole
Lalitpur, Bagmati
Nepal
Complicated Lat/Long
{27.6830282799,85.3180309269}

7. ● Subdivides space into "buckets" of grid shape
● Doesn't really represent a point, rather a bounding
area in which the point is present
● Hierarchical spatial structure with gradual degradation
● Longer the geohash
→ Smaller the area
snap taken from geohash.gofreerange.com

8. How does it work?

9. How does it work?

10. Mapping
5 bits (25
) = 32 alpha-numeric
1-9 b-z except a, i, l, o
*http://en.wikipedia.org/wiki/Geohash

11. How does it work?...
demo
snap taken from geohash.gofreerange.com

12. Lets come to our problem
● Analyze visitor from different location
Method 1:
Polygon

13. Analyze visitor from different location ...
Method 2
Geohashing
Prefix Matching

14. Other Area Where we used it
● To find duplicate Spot - O(n2
)

15. Other Application
● twitter - location based tweet count/find trend on particular location
● flickr/instagram - find location based photo with area selection on
number of prefix
● alerter system at telecommunication (integration of hardware
location + customer complain location)
● and many more...

16. References
● Geohash - http://en.wikipedia.org/wiki/Geohash

17. Thank You
twitter: @dearnarayan
email: narayan@nlocate.com