Grid Zone Designator (or GZD) - 37T GG 183126

GZDs identify a large section of the globe. 37T and 38T are highlighted in green as these are the GZDs that encompass DCS World.
Note that GZDs count from left to right, then from bottom to top.

It's a good idea to understand this principle as it applies to all parts of the MGRS coordinate.
This is because a coordinate always refers to the SOUTHWEST corner of a MGRS grid square.

Real JTACs use this statement to remember this concept:

“Right and Up”

gzdws-3
100,000 Meter Square Letter Identification - 37T GG 183126

The GG letters identify which 100,000 meter wide box inside the GZD we are looking at. Note that as you move from west-to-east the first letter increases alphabetically and from south-to-north the second letter increases alphabetically.

Note also how the GZD change bisects DCS World. This highlights the importance of always including the full MGRS coordinates during target briefing.

Observe that the Georgian capital of Tbilisi is located in grid square 38T MM.
mgrsws
The city of Batumi is located within 37T GG. To further refine it’s location the GG square is divided into 10,000 meter grid squares. Starting in GGs southwest corner, we read 2 lines (20,000 meters) to the east, then 1 line (10,000 meters) to the north and we locate grid square 37T GG 21.

Numerical Location - 37T GG 183126

The number of digits in the numerical location must always be even because the first half are the EASTING (183) and the second half are the NORTHING (126).

More numbers means a smaller grid square to search.

2 digits - 10 km - GG
11
4 digits - 1 km - GG
1812
6 digits - 100 m - GG
183126
8 digits - 10 m - GG
18351266
10 digits - 1 m - GG
1835512666

If a Numerical Location needs to be shortened they are ‘TRUNCATED’, which means
“to shorten by cutting off” the numbers that are not required.
In other words MGRS coordinates are never rounded up when shortened, the extra numbers are simply dropped from the easting and northing values.

Truncating is used because it means that the coordinates will always point to the bottom left corner of an MGRS grid square, making searching for the target easier.
Therefore to search for a target in an MGRS grid you only need to search east and north (“right and up”) from the coordinates location on the ground.

For example a T-72 at the coordinate
37T GG 1839512686 specifies a 1 meter sized square on the ground which is accurate enough for a Bomb On Coordinate (BOC) attack.
If the T-72 is part of a platoon of tanks then a 100 meter wide square would be adequate for a talk-on.
By truncating the last 2 digits from both the easting and northing we are left with
37T GG 183126.


Map Reading

Depending on the scale of the map the larger squares will be numbered with their MGRS in the centre. The grid 37T GG21 refers to the large 10,000 meter wide box that is the upper right half of the Batumi map below. When locating a smaller grid within this box you need to then combine them with this number.

For example where the river north of Batumi joins the sea you would count from left to right to
easting 3 and then up to northing 6.
Combining these numbers with the GG21 will give us 37T GG 2
316 for the 1,000 meter wide square containing the river mouth.

batumiws
Practice finding the following landmarks using their MGRS coordinates on the map above:
• Runway NW end_____37T GG
1510
• Small Lake__________37T GG 1813
• Bridge over river______37T GG 2316


Tactical Example

A Huey Scout pilot has located a ZSU-23 SHILKA inside the city of Batumi. He uses his MGRS map and identifies the target location as somewhere in the 37T GG 1812 grid square. The Hornet pilot in the overhead slews his LITENING pod to the coordinates and zooms out to view the 1,000 meter size square. The dense cluster of buildings in the area prevents him seeing the Shilka easily and he calls ‘NO JOY’.

The Huey Scout checks his map and
adds 3 units to the EASTING then 6 to the NORTHING to refine the coordinate to a 6-digit numerical location - 37T GG 183126. This has reduced the size of the search area from a 1,000 meter square down to a 100 meter square.

batumimgmapws

The images below are what the pilot saw through his LITENING pod. The 4-digit grid on the left and the 6 digit grid on the right.

Red lines have been added to illustrate the outlines of the grid squares on the ground. The smaller 100 meter wide square of the 6-digit coordinate in the right image is a much easier area to search. The F/A-18C pilot slews to the new grid, zooms in and calls ‘TALLY’ on the Shilka (yellow arrow).
lite

Note how the crosshairs are fixed on the South West corners of the squares.
Searching an MGRS grid is conducted from west to east and south to north, refer to your Northing Arrow to aide you in slewing your pod in the correct direction.



Samtredia Map Example Coordinates

MGRS map reading seems complicated at first however once you understand the basics and practice with a JTAC it becomes an easy and fast way to relate locations on the ground to other aircraft.

Try practising your new MGRS skills by locating the following landmarks on the map below:

1. MSR Michigan/Kostava road fork ______38T KM 773705
2. MSR Michigan/rail intersection ________38T KM 781704
3. Rail bridge ‘Dianna’ ________________38T KM 791706
4. FARP Dallas (Heliport) ______________38T KM 780698
samtrediamgrs2