at the equator one degree of latitude is equal to 110.574 km.
at the equator one degree of latitude is equal to?
110.574 km
since a geohash (in this implementation) is based on coordinates of longitude and latitude the distance between two geohashes reflects the distance in latitude/longitude coordinates between two points, which does not translate to actual distance, see haversine formula.









































example of non-linearity for latitude-longitude system:









































bullet::::- at the equator (0 degrees) the length of a degree of longitude is 111.320 km, while a degree of latitude measures 110.574 km, an error of 0.67%.









































bullet::::- at 30 degrees (mid latitudes) the error is 110.852/96.486 = 14.89%









































bullet::::- at 60 degrees (high arctic) the error is 111.412/55.800 = 99.67%, reaching infinity at the poles.
geohash
in 1617 the dutch scientist willebrord snell assessed the circumference of the earth at 24,630 roman miles (24,024 statute miles). around that time british mathematician edmund gunter improved navigational tools including a new quadrant to determine latitude at sea. he reasoned that the lines of latitude could be used as the basis for a unit of measurement for distance and proposed the nautical mile as one minute or one-sixtieth () of one degree of latitude. as one degree is of a circle, one minute of arc is of a circle (or, in radians, ). these sexagesimal (base 60) units originated in babylonian astronomy. gunter used snell's circumference to define a nautical mile as 6,080 feet, the length of one minute of arc at 48 degrees latitude. since the earth is not a perfect sphere but is an oblate spheroid with slightly flattened poles, a minute of latitude is not constant, but about 1861 metres at the poles and 1843 metres at the equator, with a mean value of 1852.3 metres. france and other countries measured the minute of arc at 45 degrees latitude, making the nautical mile 1852 metres.
nautical mile