MGRS Identification Letter Corrections

Many National Topographic System (NTS) map sheets have been produced with the wrong two letter MGRS designators. Our NTS sheets show the Military Grid Reference System, commonly known as the 100 000-metre square identification grid. Each 100 000-meter square is identified by a combination of two alphabetical letters. Starting at the 180° meridian and proceeding east along the equator, each 100 000-metre column is lettered alphabetically, from A through Z, with I and O omitted. Starting at the equator and proceeding north, each row is lettered alphabetically, from A through V, with I and O omitted. Reading from south to north, this lettering system is repeated every 2 000 000 metres.

In the late eighties, Natural Resources Canada decided to use the North American Datum of 1983 (NAD83), instead of the North American Datum of 1927 (NAD27), as the official datum for our mapping activities. When this change of datum occurred, we were instructed to change the lettering system for the 100 000-metre square identification grid on map sheets produced under the new datum. In the process, because of an error introduced in the lettering system, the wrong letters were shown on newly revised map sheets.