UTM, MGRS and the US National GridThe Military Grid Referencing System (MGRS) has been around since World War II and continues to be the military standard. MGRS and the USNG (US National Grid) use the long-standing Universal Transverse Mercator (UTM) projection and coordinate systems, with a different notation to make it easier and more consistent to use and communicate.

UTM divides the surface of the earth into “rectangular” zones of 6 degrees of longitude (from pole to pole) and 8 degrees of latitude. Each of these zones is then given a unique alphanumeric identifier. We are currently in zone 15S.

S does NOT mean south. It’s just a letter. North of us is 15T, west is 14S.

UTM refers to locations as a distance in meters from the lower-left corner of the zone. However, this is a lot of digits, requires full-resolution (1 meter accuracy) and there are usually more digits one way than the other.

MGRS simplfies this, first by dividing zones into 100,000-meter “squares,” each given a two-character designation formed by rows and columns of single characters. We are currently in square UD.

Then, this makes your life really easy by having only five digits each direction to specify anywhere within the grid to 1 meter precision. By convention, and because you always know how many digits, it’s also possible to use fewer. Conventional “grid reference” means you are designating a location with 1000 meter precision, and that only takes 4 digits. Anywhere in the world can be refereced with just a few letters and numbers:

Right here we’re at 15S UD 31204 87833

Taking the Easting:

3 10,000 m precision

1 1,000

2 100

0 10

4 1

Note that you don’t need the zone or square for most communications. If you are working with others inside your square, or with people who know approximately where you are, you can just use the numbers (4063) alone.

(I like to give a little pause between the Easting and Northing, and write them down with a gap but that’s just me, and is not convention per se.)

You do need to pay attention to this, however. You might be operating right next to people, but on the edge of a zone. But when possible, eliminate extra information. Especially when communicating on the radio, this is good policy, good security, and much faster.

UD

15S

100,000 M SQUAREIDENTIFICATION

GRID ZONE DESIGNATION

SAMPLE 1000 METER GRID SQUARE

Samplepoint

12 1345

46100 METER REFERENCE

WHEN REPORTING OUTSIDE THE 100,000 METER SQUARE AREA IN WHICH THE POINT LIES, PREFIX THE 100,000 METER SQUARE IDENTIFICATION.

Example: WD123456

WHEN REPORTING OUTSIDE THE G RID ZONE DESIGNATION AREA I N WHICH THE POINT LIES, PREFIX THE GRID ZONE DESIGNATION.

Example: 15SWE123456

1. Read large numbers labeling the VERTICAL grid line left of t he p oint a nd e stimate tenths ( 100 meters) from gridline to point. 123

2. Read large numbers labeling the HORIZONTAL grid l ine below the point and estimate t enths (100 meters) f rom gridline to point. 456

Example: 123456

Reading Grids off MapsGrids on military issue maps are drawn every 1000 m, and each line is labeled. Every tenth line is heavier, and the numbers are repeated inside the map as well, to make it easier to read on large sheets.

Our maps have some extra numbers, to support UTM, and because our grids are at 100 meter intervals (because we operate on smaller land, and do everything on foot).

To read grids, look across first (left to right) then up. Demonstrate. Everyone does this themselves.

Lat/long, in the manner used by the Air Force (but not the Navy... they use a different notation style), is also listed on the maps. The corners, and small ticks along the edge, note that coordinate system. If you work in or with the Air Force, you will need to draw in these grid lines, and learn how that system works. But we won’t as it’s very different.

Precision Level 1 – Reference pointsGrid squares are pretty big. You usually need more precision than this. One easy way to note it is to find something unique and unambiguous inside the grid. For this example, “the trail intersection shown on the map at 510732“ is pretty clear. This of course will only work for some cases. It’s hard to drop GPS-guided bomb on those coordinates. But it’s good for talking quickly to your immediate higher, or the next squad over.

Precision Level 2 – 100, 10, 1 m CoordinatesGrid squares can be subdivided, using guesswork, straightedges, measuring tools or better yet, your issued “roamer” or “protractor.”

See the example chart on the previous page, discussing subdividing a grid square. v

LIMIT OF OPERATIONS AREA

LIMIT OF OPERATIONS AREA

LIMIT OF OPERATIONS AREA

LIMIT OF OPERATIONS AREALIMIT OF OPERATIONS AREA

LIMIT OF OPERATIONS AREALIMIT OF OPERATIONS AREA

LIMIT OF OPERATIONS AREA

LIM

IT O

F O

PE

RAT

ION

S A

RE

A

LIM

IT O

F O

PE

RAT

ION

S A

RE

A

LIM

IT O

F O

PE

RAT

ION

S A

RE

A

4068000m N

350000m E 351000m E349000m E

500

500

500

510

510

510

4069000m N

4068000m N

4069000m N

352000m E

700700700

690690690

500 510

4071000m N

4070000m N

4071000m N

4070000m N

710710710

350000m E 351000m E 352000m E

4072000m N

349000m E

4072000m N

94°39’35.5”94°40’94°41’

94°41’32”

94°39’32.3”

94°41’

94°41’30.06”

94°40’

36°46’

36°45’

36°46’56.1”

36°44’45.8”

36°46’

36°45’

36°46’55.8”

36°44’43.9”

3501 3502 3503 3504 3505 3506 3507 3508 3509 3511 3512 3513 3514 3515 3516 3517 3518 3519349934983497349634953494349334923491

3501 3502 3503 3504 3505 3506 3507 3508 3509 3511 3512 3513 3514 3515 3516 3517 3518 3519349934983497349634953494349334923491

40719

40718

40717

40716

40715

40714

40713

40712

40711

40709

40708

40707

40706

40705

40704

40703

40702

40701

40699

40698

40697

40696

40695

40694

40693

40692

40691

40689

40688

40687

40686

40685

40684

40683

40682

40681

40719

40718

40717

40716

40715

40714

40713

40712

40711

40709

40708

40707

40706

40705

40704

40703

40702

40701

40699

40698

40697

40696

40695

40694

40693

40692

40691

40689

40688

40687

40686

40685

40684

40683

40682

40681

HELIPORTEDAP/5/S

1020

BSDDAP

Drava

Loange

LUCALA

KASAI

CALABAR

Vehlefanz

Destroyed

22

231 23

25

20

21

19

17

17

27

15

27

201

171

18

183

181

182

19

19

176

19

Nibelungenalle

17

17173

176B

25

29

29

25

34

R49

R49

34

R49

36

36

29

29

R49

28281

22

22

28

30

15

15

15

R49

15W15E

CONTOUR INTERVAL 10 FEET

Scale 1:7,500

ROADS

Secondary all weather,hard surface, two or more lanes wide

Light duty, all weather, improved surface

Light duty, seasonal, unimproved surface

Trail or unimproved surface road

Route markers: State highway

BOUNDARIES

Reservation: military operations area

Fenceline

Power transmission line

Occupied permanent dwellings

Unoccupied buildings or structures

Horizontal control station

Bench mark, monumented

Bench mark, non-monumented

Spot elevations in feet: checked; unchecked

Woodland

Vineyard; Orchard

Pond

Intermittent pond or lake

Intermittent stream

Unclassified stream

792

817

BM

LIMIT OF OPERA

SPHEROID . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CLARKE 1866GRID . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 M UTM ZONE 15PROJECTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . TRANSVERSE MERCATORVERTICAL DATUM . . . . . . . . . . . . . NATIONAL GEODETIC VERTICAL DATUM OF 1929HORIZONTAL DATUM . . . . . . . . . . . . . . . . . . . . . . . . . . . WORLD GEODETIC SYSTEM 84CONTROL BY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . USGS, USC&GS & DMAPREPARED BY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . KCAA GIS AUTHPRINTED BY . . . . . . . . . . DEFENSE MAPPING AGENCY TOPOGRAPHIC CENTER 7 84

UA

15S

100,000 M SQUAREIDENTIFICATION

GRID ZONE DESIGNATION

SAMPLE 1000 METER GRID SQUARE

Samplepoint

12 1345

46100 METER REFERENCE

WHEN REPORTING OUTSIDE THE 100,000 METER SQUARE AREA IN WHICH THE POINT LIES, PREFIX THE 100,000 METER SQUARE IDENTIFICATION.

Example: WD123456

WHEN REPORTING OUTSIDE THE GRID ZONE DESIGNATION AREA IN WHICH THE POINT LIES, PREFIX THE GRID ZONE DESIGNATION.

Example: 15SWE123456

1. Read large numbers labeling the VERTICAL grid line left of the point and estimate tenths (100 meters) from gridline to point. 123

2. Read large numbers labeling the HORIZONTAL grid line below the point and estimate tenths (100 meters) from gridline to point. 456

Example: 123456

GN

TO CONVERT A MAGNETIC

AZIMUTH TO A GRID AZIMUTH SUBTRACT G-M

ANGLE

TO CONVERT A GRID AZIMUTH TO

A MAGNETIC AZIMUTH ADD G-M ANGLE

2008G-M ANGLE

1°1’ (18 MILS)

GRID CONVERGENCE 2°39’ (47 MILS) FOR CENTER OF

SHEET

0 100 200 300 400 500 Meters100 500

0 100 200 300 400 500 Yards100 500

0 1/8 1/4 Statute Mile

EAST MAROS EDITION 6–DMA SERIES V734 SHEET 2013 IIIARDEA 1:7,500

THIS MAP IS RED-LIGHT READABLE

DMA STOCK NO. V7781X21546 ED.NO. 021EDITION 6–DMA SERIES V734 SHEET 2013 III

One second of longitude equals 24.36 mUnlabeled ticks are 10 second increments

LEGENDCOMPILED IN 1978 FROM BEST AVAILABLE SOURCES

ON THIS MAP, A LANE IS GENERALLY CONSIDERED AS BEING A MINIMUM OF 2.5 METERS (8 FEET) IN WIDTH

Prepared and published by the Defense Mapping AgencyTopographic Center, Bethesda, MD.

ELEVATION GUIDE

High

Medium

Low

ADJOINING SHEETS

2013 III1913 II 2013 II

2012 IV 2012 I1912 I

2013 IV 2013 I1913 I

E 813 725

One

sec

ond

of l

atitu

de

equa

ls 3

1.3

m

One

sec

ond

of l

atitu

de

equa

ls 3

1.3

m

TRUE NORTH

GRID NORTH

MAG

NETI

C NO

RTH

DeclinationDeclination is a complexity induced upon you because our north-seeking device doesn’t work off Grid north, the lines where our MGRS GRID is aligned, but off magnetic north.

The magnetic north pole wanders about, and as a result of the geometry of trying to represent the round earth on flat maps.

Luckily, you don’t have to do the math, and every military map (and many others) has a declination chart in the corner, giving you the numbers. There are several kinds: USGS and U.S. military maps are to (angular) scale and aligned with a grid line, others (e.g. Russian) are not. The sample here is a U.S. Military one.

To adjust, put the compass on the map, aligned with GN. Twist the capsule (or declination adjustment) so the capsule aligns with MN.

GN is Grid North, or the north/south axis against which all the lines in the UTM Zone grid are aligned. These are different for each Zone or map sheet, so read your map each time.

TN is True North. This is often marked with a star, and points to the location where all the longitude lines converge at the North Pole (which is more or less the axis about which the earth spins). This is the “grid” upon which lat/long measurements are taken. If using lat/long – like if you are working with the USAF – you will need to adjust directions to True North, not Grid North. But we do not care about True North.

MN is Magnetic North, (often marked with an arrow) and corresponds to where your compass points. The declination chart is accurate ONLY at one point. Sometimes this is the center of the Zone, but for military charts it tends to be at the center of the sheet, or the actual piece of paper you are issued. This often will not matter a lot, but if you are working somewhere with 80° declination, it will change by several degrees as you move across sheets; driving for an hour can change declination a great deal.

Magnetic north moves about all the time. You need to look for the date the map was published; sometimes the date is immediately adjacent to the declination scale for this exact reason. In high declination areas, it can put you off by miles, even when traveling by foot, after just a few years.

In general, it’s good to remember that Zones simulate being flat, 2D sheets so the grids are all square. But this is a cheat so there is some inaccuracy, and projection inaccuracy gets more severe as you approach the poles. If you will be operating in arctic areas, try to get familiar with the navigation methods needed in such environments.

LIMIT OF OPERATIONS AREA

LIMIT OF OPERATIONS AREA

LIMIT OF OPERATIONS AREA

LIMIT OF OPERATIONS AREALIMIT OF OPERATIONS AREA

LIMIT OF OPERATIONS AREALIMIT OF OPERATIONS AREA

LIMIT OF OPERATIONS AREA

LIM

IT O

F O

PE

RAT

ION

S A

RE

A

LIM

IT O

F O

PE

RAT

ION

S A

RE

A

LIM

IT O

F O

PE

RAT

ION

S A

RE

A

4068000m N

350000m E 351000m E349000m E

500

500

500

510

510

510

4069000m N

4068000m N

4069000m N

352000m E

700700700

690690690

500 510

4071000m N

4070000m N

4071000m N

4070000m N

710710710

350000m E 351000m E 352000m E

4072000m N

349000m E

4072000m N

94°39’35.5”94°40’94°41’

94°41’32”

94°39’32.3”

94°41’

94°41’30.06”

94°40’

36°46’

36°45’

36°46’56.1”

36°44’45.8”

36°46’

36°45’

36°46’55.8”

36°44’43.9”

3501 3502 3503 3504 3505 3506 3507 3508 3509 3511 3512 3513 3514 3515 3516 3517 3518 3519349934983497349634953494349334923491

3501 3502 3503 3504 3505 3506 3507 3508 3509 3511 3512 3513 3514 3515 3516 3517 3518 3519349934983497349634953494349334923491

40719

40718

40717

40716

40715

40714

40713

40712

40711

40709

40708

40707

40706

40705

40704

40703

40702

40701

40699

40698

40697

40696

40695

40694

40693

40692

40691

40689

40688

40687

40686

40685

40684

40683

40682

40681

40719

40718

40717

40716

40715

40714

40713

40712

40711

40709

40708

40707

40706

40705

40704

40703

40702

40701

40699

40698

40697

40696

40695

40694

40693

40692

40691

40689

40688

40687

40686

40685

40684

40683

40682

40681

HELIPORTEDAP/5/S

1020

BSDDAP

Drava

Loange

LUCALA

KASAI

CALABAR

Vehlefanz

Destroyed

22

231 23

25

20

21

19

17

17

27

15

27

201

171

18

183

181

182

19

19

176

19

Nibelungenalle

17

17173

176B

25

29

29

25

34

R49

R49

34

R49

36

36

29

29

R49

28281

22

22

28

30

15

15

15

R49

15W15E

CONTOUR INTERVAL 10 FEET

Scale 1:7,500

ROADS

Secondary all weather,hard surface, two or more lanes wide

Light duty, all weather, improved surface

Light duty, seasonal, unimproved surface

Trail or unimproved surface road

Route markers: State highway

BOUNDARIES

Reservation: military operations area

Fenceline

Power transmission line

Occupied permanent dwellings

Unoccupied buildings or structures

Horizontal control station

Bench mark, monumented

Bench mark, non-monumented

Spot elevations in feet: checked; unchecked

Woodland

Vineyard; Orchard

Pond

Intermittent pond or lake

Intermittent stream

Unclassified stream

792

817

BM

LIMIT OF OPERA

SPHEROID . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CLARKE 1866GRID . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 M UTM ZONE 15PROJECTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . TRANSVERSE MERCATORVERTICAL DATUM . . . . . . . . . . . . . NATIONAL GEODETIC VERTICAL DATUM OF 1929HORIZONTAL DATUM . . . . . . . . . . . . . . . . . . . . . . . . . . . WORLD GEODETIC SYSTEM 84CONTROL BY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . USGS, USC&GS & DMAPREPARED BY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . KCAA GIS AUTHPRINTED BY . . . . . . . . . . DEFENSE MAPPING AGENCY TOPOGRAPHIC CENTER 7 84

UA

15S

100,000 M SQUAREIDENTIFICATION

GRID ZONE DESIGNATION

SAMPLE 1000 METER GRID SQUARE

Samplepoint

12 1345

46100 METER REFERENCE

WHEN REPORTING OUTSIDE THE 100,000 METER SQUARE AREA IN WHICH THE POINT LIES, PREFIX THE 100,000 METER SQUARE IDENTIFICATION.

Example: WD123456

WHEN REPORTING OUTSIDE THE GRID ZONE DESIGNATION AREA IN WHICH THE POINT LIES, PREFIX THE GRID ZONE DESIGNATION.

Example: 15SWE123456

1. Read large numbers labeling the VERTICAL grid line left of the point and estimate tenths (100 meters) from gridline to point. 123

2. Read large numbers labeling the HORIZONTAL grid line below the point and estimate tenths (100 meters) from gridline to point. 456

Example: 123456

GN

TO CONVERT A MAGNETIC

AZIMUTH TO A GRID AZIMUTH SUBTRACT G-M

ANGLE

TO CONVERT A GRID AZIMUTH TO

A MAGNETIC AZIMUTH ADD G-M ANGLE

2008G-M ANGLE

1°1’ (18 MILS)

GRID CONVERGENCE 2°39’ (47 MILS) FOR CENTER OF

SHEET

0 100 200 300 400 500 Meters100 500

0 100 200 300 400 500 Yards100 500

0 1/8 1/4 Statute Mile

EAST MAROS EDITION 6–DMA SERIES V734 SHEET 2013 IIIARDEA 1:7,500

THIS MAP IS RED-LIGHT READABLE

DMA STOCK NO. V7781X21546 ED.NO. 021EDITION 6–DMA SERIES V734 SHEET 2013 III

One second of longitude equals 24.36 mUnlabeled ticks are 10 second increments

LEGENDCOMPILED IN 1978 FROM BEST AVAILABLE SOURCES

ON THIS MAP, A LANE IS GENERALLY CONSIDERED AS BEING A MINIMUM OF 2.5 METERS (8 FEET) IN WIDTH

Prepared and published by the Defense Mapping AgencyTopographic Center, Bethesda, MD.

ELEVATION GUIDE

High

Medium

Low

ADJOINING SHEETS

2013 III1913 II 2013 II

2012 IV 2012 I1912 I

2013 IV 2013 I1913 I

E 813 725

One

sec

ond

of l

atitu

de

equa

ls 3

1.3

m

One

sec

ond

of l

atitu

de

equa

ls 3

1.3

m

TRUE NORTH

GRID NORTH

MAG

NETI

C NO

RTH