how long can a MGRS coordinate be?

Answer 1

Most land navigation activities focus on a very small portion of the globe at any one time. Typically the area of interest to an outdoorsman is less than 20 miles on a side. This focus on a small area allows us to abbreviate UTM coordinates.

The zone information and the digits representing 1,000,000m, and 100,000m are dropped. The 1m, 10m and 100m digits are used only to the extent of accuracy desired.

A GPS unit might read

10 S 0559741
4282182

Using a notation similar to the one found on a USGS topographic map, this would be written as:

Zone 10 S 559741 mE. 4282182 mN.

An abbreviated format for the same coordinates would look like:

59 82
Describes a 1000m by 1000m square.

597 821
Describes a 100m by 100m square.

5974 8218
Describes a 10m by 10m square.

59741 82182
Describes a 1m by 1m square.


The 100m abbreviated format, 597 821, and the 10m abbreviated format, 5974 8218, are the most commonly used.

Notice that the easting is reported first, followed by the northing. Remember the phrase "read right up" to help you remember to read the easting from left to right, followed by the northing from the bottom up.

Also notice that when you abbreviate coordinates you should not do any rounding. 0559651 becomes 596 not 597. This ensures that your position is still within the reported square. As accuracy decreases, the square gets bigger.

I hope this is what you are looking for.