GeoHashes

Geohashes can be thought of as rectangular subdivisions of the Earth's surface. Learn more here: Geohash at Wikipedia. They were invented by Gustavo Niemeyer in 2008.

A degree of latitude is ~111.3km anywhere on earth. A degree of longitude varies depending on your latitude, but at the equator, it is also ~111.3km.

Dimensions in lon,lat of geohashes of length n:

N	Longitude	Latitude	east/west distance at equator	north/south distance at equator
12:	0.00000033527612686157227	0.00000016763806343078613	~3.7cm	~1.8cm
11:	0.000001341104507446289	0.000001341104507446289	~14.9cm	~14.9cm
10:	0.000010728836059570312	0.000005364418029785156	~1.19m	~0.60m
9:	0.00004291534423828125	0.00004291534423828125	~4.78m	~4.78m
8:	0.00034332275390625	0.000171661376953125	~38.2m	~19.1m
7:	0.001373291015625	0.001373291015625	~152.8m	~152.8m
6:	0.010986328125	0.0054931640625	~1.2km	~0.61km
5:	0.0439453125	0.0439453125	~4.9km	~4.9km
4:	0.3515625	0.17578125	~39km	~19.6km
3:	1.40625	1.40625	~157km	~157km
2:	11.25	5.625	~1252km	~626km
1:	45	45	~5018km	~5018km

IGNORE THE FOLLOWING NUMBERS

They're wrong - i used x,y instead of lat/lon, and as a result they're only valid for Rome; projected values are location-specific. But they're interesting anyways and I wasted a half-hour on them so I'm saving them.

N	x	y
12:	0.03352761268615723	0.022274659015238285
11:	0.1341104507446289	0.1781972600147128
10:	1.0728836059570312	0.7127890586853027
9:	4.291534423828125	5.702313330955803
8:	34.332275390625	22.809258637949824
7:	137.3291015625	182.4745806204155
6:	1098.6328125	729.8819535905495
5:	4394.53125	5838.531777993776
4:	35156.25	23348.537284125574
3:	140625	187680.11060012504
2:	1125000	744941.5192134883
1:	4500000	6966582.671835422