Geohash Brief Introduction...

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