Map Reading: The Military Grid Reference System (MGRS)

Military reference topographical maps use grids to determine location and relay critical information. 

These grids are compiled into a measurable method for navigating using maps and calculating locations (and the distance between locations) known as the military grid reference system. 

Using Grids to Determine Accuracy

The grid is split into several sub-sectors to help you identify the accuracy of a location and pinpoint a specific spot on the map:

Grid Zone Designator - The world divided into 60 alpha-numeric panels to determine a geographical area

Grid Reference - A letter-designated "square" of 100,000 meters (100 kilometers, or approximately 62.14 miles)

2-Digit Grid Coordinate - 10,000 meters (10 kilometers, or approximately 6.21 miles)

4-Digit Grid Coordinate - 1,000 meters (1 kilometer, or approximately 0.62 miles)

6-Digit Grid Coordinate - 100 meters (0.1 kilometers, or approximately 328 feet)

8-Digit Grid Coordinate - 10 meters (approximately 33 feet)

10-Digit Grid Coordinate - 1 meter (approximately 3.3 feet)

Reading Grid Coordinates

When reading grids, and when relaying coordinates via communication, they are always references "right-then-up" or "east-then-north," much like plotting on a graph. 

Grid Coordinates are read as Grid Zone | Grid Reference | Coordinates (in prescribed digits). 

Example:
Using the map below, determine the grid coordinate for the crosshair point. Approximately the location to 100 meters. 

This map uses Grid Reference MF inside of Grid Zone 17T. 

An approximation of 100 meters uses a 6-digit grid coordinate. 

Start off by reading the lateral (horizontal) numbers, going toward the right to approximate the position. The crosshairs above look like they are around 25.3, or 253. 

Then, read upward along the vertical numbers. It looks like the crosshairs are close to the 53.0 line, or 530. 

The crosshairs are over Grid Coordinate 17T MF 253 530.