Os gridref (tag)
From SnapMap
os_gridref is used to declare a photo to be within a certain Ordnance Survey grid square. This coordinate system uses the British national grid reference system.
The format is two letters, followed by an even number of digits, to reach any level of precision.
Example
- os_gridref = ST5673 denotes a 1km x 1km square in Bristol, England.
- os_gridref = ST56817392 denotes a 10m x 10m square in Bristol, England. This is the highest level of detail likely to be of use in photos located by GPS or using a map layer.
The granularity can be increased by a factor of two by another tag, os_gridref_quadrant, which takes one of NE, NW, SE, SW as values, and identifies a quadrant within the square defined by os_gridref.
