A 10km x 10km UTM NAD83 grid that is a standard reference index for Ontario. It includes a Military Grid Reference, Fire Base Map identifier, Atlas identifier, and an UTM Map Sheet Number.

UTM Map Sheet Number - Identification number of a UTM Mapsheet. This code is comprised the first 2 digits of the scale (e.g. 20 = 1:20,000), the Utm zone number, the first four digits of the UTM Easting, and the first five digits of the UTM Northing. (e.g. 2017610051100).