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a. General.
A grid system is a two-dimensional plane-rectangular coordinate system that is usually based on, and mathematically adjusted to, a map projection. This allows for the transformation from geodetic positions (latitude and longitude) to plane coordinates (easting and northing) and for the computations relating to those coordinates to be made by ordinary methods of plane surveying. b. Local and Universal Grids.
Currently there are many grid systems in use. The majority of the "local" systems will eventually be converted to one of the universal grid systems, while some areas will continue to be mapped in a local system such as the
British National Grid (BNG), the Irish Transverse
Mercator Grid (ITMG), and the Madagascar Grid
(MG). There are two universal grids used by the US military and its allies: Universal Transverse
Mercator (UTM) and Universal Polar
Stereographic (UPS) . c. Grid Lines.
Grids consist of a system of evenly spaced parallel lines lying perpendicular to another system of evenly spaced parallel lines forming squares. The ground distance between the lines is dependent on the scale of the map and the type of grid system. Most systems use meters as a basis for grid line spacing; while others use yards or feet.
Standard scale military maps generally adhere to the following: grid lines on large scale maps are spaced at 1000 meters, grid lines on medium scale maps at
1:250,000 are spaced at 10,000 meters. For scales smaller than 1:250,000, the grid lines may or may not be depicted, dependent on the purpose of the map. d. Grid Line Values.
The north-south lines in a grid system are called Eastings and increase in value from west to east. The east-west lines in a grid system are called Northings and their value increases from south to north. (These rules do not apply to grid systems that cover the Polar Regions such as the UPS.) The numerical value of an easting and northing are referenced to a specific origin. A false value is applied to the easting or northing grid line that falls at a particular reference line or point. Usually, that line or point is a meridian of longitude (e.g. central meridian of a zone) or a parallel of latitude (e.g. equator); but it can have other references.
The origin for the false easting and false northing are normally different lines or points.
Grid convergence is the angular difference between true north and grid north. The direction and the value of the angle is computed differently depending on the grid system. In some grid systems, grid convergence can be considered the same as convergence of the meridians.
a. The Universal Transverse Mercator (UTM)
Grid System is referenced to the Transverse
Mercator Projection. The ellipsoid is divided into 60 grid zones, each 6° wide, extending from 84° N latitude to 80° S latitude. The zones are numbered from 1 to 60, with zone 1 starting at 180°- 174° W longitude, zone 2 at 174° W - 168° W longitude, continuing east to zone 60 at 174° E - 180° longitude.
The Prime Meridian (0° longitude) separates zones
30 and 31. (See Figure 3-17.) b. The location of any point in the UTM grid system can be designated by coordinates by giving its distance east west (easting) and its distance northsouth (northing) from the origin of the grid zone.
This origin, for each UTM grid zone, is the intersection of the equator and the central meridian of the zone. Each UTM zone has a central meridian corresponding to the central meridian of each
Transverse Mercator Projection zone. The grid is oriented by placing the east-west axis of the grid in coincidence with the Equator and the north-south axis of the grid in coincidence with the central meridian of the zone. c. Once the grid is oriented, the origin for easting and northing are assigned false values. The central meridian (origin for easting) of each zone is assigned an easting value of 500,000 meters. The easting increases east of the central meridian and decreases west. The Equator (origin for northing) is assigned two false values; if you are operating in the northern hemisphere the northing of the equator is 0 meters and increases north, if you are in the southern hemisphere the northing of the equator is 10,000,000 meters and decreases south. Grid lines that run north

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Figure 3-17 UTM/UPS Grid Zones and Grid Zone Designators

and south are easting lines; these lines are parallel to the central meridian of the grid zone. Grid lines that run east and west are northing lines; these lines are parallel to the equator. (See Figure 3-18.)
84° N
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(6253II) lists it at 4 mils; there are two mils difference between the centers of these two adjoining sheets. (See Figure 3-19.)
NORTH POLE
GN = TN
GN GN GN GN GN GN
6,000,000mN
5,000,000mN
4,000,000mN
3,000,000mN
2,000,000mN
1,000,000mN
0mN
EQUATOR
10,000,000mN
9,000,000mN
GN
GRID
CONVERGENCE
6°
8,000,000mN
7,000,000mN
6,000,000mN
5,000,000mN
4,000,000mN
80° S
Figure 3-18 UTM Easting and Northing d. Grid Convergence.
1. Grid convergence at a point in the UTM system is the angle measured, east or west, from true north to grid north. At any point along the central meridian of a UTM grid zone, true north and grid north are the same. At any point not located on the central meridian, grid north departs from true north because of convergence of the meridians. Grid convergence within the UTM system is a function of both latitude and longitude. It will rarely exceed 3°
(53.333 mils) and is normally listed in the declination diagram of a map. Grid convergence should be computed for use in 5th order or higher surveys because the information on the map is generally computed for the center of the map sheet. For example, the Lawton map sheet (6353III) lists the grid convergence at 6 mils, the Cache map sheet
SOUTH POLE
Figure 3-19 UTM Grid Convergence
2. In the northern hemisphere, grid convergence is considered negative east of the central meridian and positive west. In the southern hemisphere, grid convergence is considered to be positive east of the central meridian and negative west. The direction (+,
-) and the value of the grid convergence is applied to a true azimuth to obtain a grid azimuth. If a grid azimuth must be converted to a true azimuth, the value of the grid convergence is the same; however, the opposite sign (direction) must be used. (See
Figure 3-20.)
Figure 3-20 Sign of Grid Convergence

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Figure 3-21 Non-Standard UTM Grid Zones e. Non-standard Zones.
The standard UTM grid zone is 6° wide; however, portions of several grid zones have been modified to accommodate southwest
Norway and the islands of Svalbard. These grid zone modifications are not available in many survey or fire support systems, so user defined options or work around methods must be used in those areas. Figure
3-21 depicts the non-standard portions of the respective grid zones. f. UTM Grid Coordinates.
1. The Easting and Northing values of a point in the UTM grid system are called Grid Coordinates .
The easting will consist of six digits before the decimal point. The only exception to this is positions which are actually located in an adjacent grid zone.
An easting can be written with the first digit (100,000 meters) separated from the next five with a space.
The northing will generally have seven digits before the decimal point. The exception to this is at locations north of the equator by less than 1,000,000 meters. A Northing can be written with the first two digits (1,100,000 meters) separated from the next five digits with a space. The number of digits after the decimal point is dependent on the order of survey and the accuracy needed. An example of a UTM grid coordinate is 6 39127.84 - 38 25411.24.
2. If at any time you cross the equator from north to south (at which point you would have a negative northing), you must algebraically add the northing to ten million meters to obtain a northing for the southern hemisphere. If you cross the equator from south to north (which would produce a northing greater than ten million meters), you must subtract ten million meters from your northing to obtain a northing that can be used in the northern hemisphere.
a. The Universal Polar Stereographic (UPS) Grid
System is referenced to the Polar Stereographic
Projection. It is used to map the polar regions of the earth north of 84° N latitude and south of 80° S latitude. b. Each polar region is a grid zone. The two zones are not numbered as in the UTM system; they are merely referred to as the North and South grid zone . The origin for each UPS grid zone is the pole
(North or South). The grid is oriented by placing the

Figure 3-22 UPS North and South Grid Zones
DRAFT east-west axis of the grid in coincidence with the
90°W and 90°E meridians and the north-south axis of the grid in coincidence with the 0° and 180° meridians. (See Figure 3-17.)

DRAFT c.
The location of any point on a UPS grid can be designated by coordinates by giving its distance eastwest (easting) of the 0° and 180° meridians or northsouth (northing) of the 90°W and 90°E meridians. A value of 2,000,000 meters is assigned to the meridians for both easting and northing. The easting value increases from two million meters toward the eastern hemisphere and decreases toward the western hemisphere in both grid zones. The northing value in the North grid zone increases from two million meters in the direction of the International Dateline (180° longitude) and decreases in the direction of the Prime
Meridian (0° longitude). In the South grid zone, the northing value increases from two million meters in the direction of the Prime Meridian and decreases in the direction of the International Dateline. (See
Figure 3-22.) d. Grid Convergence.
1. In the North zone, grid north is the direction toward the North Pole along the 0° meridian and the direction away from the North Pole along the 180° meridian. In the South zone, grid north is the direction toward the South Pole along the 180° meridian and the direction away from the South Pole along the 0° meridian. For any points not on the 0° and 180° meridians, grid north is the northern direction of a line through the point which is parallel to those meridians.
2. All meridians of longitude are straight lines radiating from the center of the grid (North and South zone). These lines are true north-south lines; therefore, the direction of true north at a point is the same as the longitude at that point.
3. As with the UTM system, grid convergence is the angle from a true north line to a grid north line.
Grid north is the same as true north along the 0° meridian. Grid north is in the opposite direction of true north along the 180° meridian. Grid convergence increases east and west of 0° to 180°.
The value of grid convergence at any point in the
UPS system is equal to the longitude of that point and is expressed as an angular measure east or west as measured from true north. (See Figure 3-23.)
90° W
90° W
84°
GN
NORTH
POLE
GRID CONVERGENCE 40° E
90° E
0°
NORTH ZONE
SOUTH ZONE
0°
SOUTH
POLE
180°
GN
40° E
TN
GRID CONVERGENCE 130° W
90° E
80°
130° E
TN
180°
Figure 3-23 UPS Grid Convergence e. UPS Grid Coordinates.
In the UPS grid system, both eastings and northings will consist of seven digits before the decimal point. The first two digits
(1,100,000 meters) can be separated from the next five by a space. The number of digits following the decimal point is dependent upon the order of survey and the accuracy needed. An example of a UPS grid coordinate is 17 81256.41 - 26 41416.82.
a. General.
As with the Transverse Mercator and
Polar Stereographic Projections, the UTM and UPS systems provide for a one degree overlap; each system continuing into the other for 30 minutes. b. UTM/UPS.
The standard limits of the UTM and
UPS grid systems are at 84° N and 80° S latitude. A
30-minute overlap extends the UTM to 84° 30' N and
80° 30' S latitude. The UPS is extended 30 minutes to 83° 30' N and 79° 30' S latitude.

a. The Gauss-Kruger (GK) Grid System is referenced to the Gauss-Kruger (Transverse Mercator
- tangent) projection. The GK grid can be considered a universal grid, like UTM and UPS. It is actually a local grid covering Europe, the Middle East, Asia, and parts of Africa. The grid is usually placed on a projection using one of the following reference ellipsoids:
Krassovsky: Russia (all former USSR), Albania after 1945, Afghanistan, Bulgaria, China to 1981,
Czechoslovakia, Germany, Hungary, Laos, Poland,
Romania, and Somalia
GRS (China) 1980: China after 1981
Bessel: Albania through 1945, Austria, Germany,
and North Korea b. The GK grid has many similarities to the UTM grid.
1. Each GK grid zone is 6° wide and they are numbered from 1 to 60. The zones start at the Prime
Meridian (0° longitude) instead of the International
Dateline (180° longitude). This difference offsets the grid zone numbers by 30; therefore, UTM grid zone 6 is the same as GK grid zone 36.
2. The central meridian of each GK grid zone is the same as the central meridian of each UTM grid zone.
3. The north and south limits of the GK grid have not been rigidly defined but it is generally accepted that the limits are similar to those of the UTM grid system.
4. Grid convergence is the same for a GK grid coordinate as it is for the corresponding UTM coordinate. c. The origin for coordinates is the same in the GK system as the UTM system, the false value applied to the equator is the same in both systems, but the easting is slightly different. The false value applied to the central meridian is 500,000, like UTM, with the grid zone number added to the millions place.
For example, the easting value of the central meridian in GK grid zone 6 is 6,500,000 meters.
DRAFT d. GK Grid Coordinates.
A GK grid coordinate is expressed with the northing written before the easting. The northing is written with seven digits before the decimal point with and may have a space between the first two and the next five digits. The easting is written with the grid zone first, then with six digits before the decimal point. A space can be placed between the 100,000-meter place and the next five digits. An example of a GK grid coordinate in zone 5 is: 38 25411.24 - 56 39127.84. (This example uses the same numbers as the example for a
UTM coordinate, para 3-13,f,1.)
a. General.
Simply applying the UTM scale factor to the GK grid can perform conversions from the GK grid to the UTM grid. The UTM and GK grids are both referenced to the same projection (the
Transverse Mercator Projection and Gauss-Kruger
Projection can be considered the same), the only difference being that the UTM grid is oriented to a secant cylinder while the GK grid is oriented to a tangent cylinder. Since both grid systems use the same central meridians in each zone, and since the false values applied to the origins for easting and northing are basically the same, the only major difference to be considered is the scale factor. The
Gauss-Kruger Projection has a scale factor of 1.00
(exact or unity) at the central meridian of each zone, while the scale factor for the central meridian in each
Transverse Mercator Projection zone is 0.9996. b. Procedures.
To convert a GK grid coordinate to a UTM grid coordinate, use the following steps:
EASTING
Step 1: Drop the GK grid zone from the millions
place.
Step 2: Subtract 500,000 meters from the GK
easting. (If the point is west of the central meridian, the result will be a negative number.)
Step 3: Multiply the result in Step 2 by 0.9996.
Step 4: Add 500,000 meters to the result of Step
3.
Step 5: Determine UTM grid zone by adding or
subtracting 30 from the GK grid zone. (The result must be between 1 and 60 inclusive.)

NORTHING
(NORTH OF EQUATOR)
Step 1: Multiply the GK northing by 0.9996.
(SOUTH OF EQUATOR)
Step 1: Subtract 10,000,000 meters from the GK
northing. (The result will be negative.)
Step 2: Multiply the result of Step 1 by 0.9996.
Step 3: Add 10,000,000 meters to the result of
Step 2.
** NOTE ** The resulting easting and northing coordinates will be referenced to the UTM grid system in the same ellipsoid and datum as the GK coordinates.
a.
UTM, GK and UPS grid coordinates are not unique. Any UTM grid coordinates can be plotted in each of the 60 grid zones; additionally many UTM and GK coordinates will plot in both the northern and southern hemispheres of the same grid zone. All UPS grid coordinates between 84° and 90° N and S latitudes will plot in each of the two UPS grid zones. b. To make UTM and UPS grid coordinates unique, the grid zone and grid zone designator should accompany them.
a. General.
The Military Grid Reference System
(MGRS) is designed for use with the UTM and UPS grid systems. It establishes a unique set of coordinates for each specific location on the Earth.
An MGRS grid coordinate consists of a grid zone
(UTM only), a grid zone designator, a 100,000-meter square identifier, and the easting/northing coordinate. b. Grid Zone Designator . A grid zone designator is a one-letter code specifying a particular portion of a
UTM/UPS grid zone. The grid zone designator is usually listed in the marginal data of a military map.
(See Figure 3-17.)
1. UTM.
Each of the 60 UTM grid zones are divided into 20 grid zone designators, each designator representing an 8° portion of the grid zone except the northernmost representing 12°. The designators are
DRAFT identified alphabetically by the letters C to X with the letters I and O omitted. C is the southernmost designator, X is the northernmost, and the equator separates M and N. Thus, a grid zone and grid zone designator together specify a region of the Earth covering a 6° by 8° area except in the northernmost designation (X) which specifies a 6° by 12° area.
2. UPS.
Both UPS zones (North and South) are divided into two grid zone designations separated by the 0° and 180° meridians. In the north zone, the designator Y covers the western hemisphere, Z covers the eastern hemisphere. In the south zone, designator
A covers the western hemisphere, B the eastern hemisphere. Since numbers are not used to identify the UPS grid zones, a UPS grid MGRS coordinate will begin with the grid zone designator. c. 100,000 Meter Square Identifier.
Each
UTM/UPS grid zone is divided into 100,000-meter squares. These squares are identified by two letters called a 100,000-meter square identifier . The first letter is columnar ; it is the same for all squares in a north-south column. The second letter is linear ; it is the same for all squares in an east-west row in a grid zone. This identifier is usually listed as part of the marginal information on a military map. The lettering convention used is dependent on the reference ellipsoid. This text will discuss the UTM lettering convention used with the WGS 84 and GRS 80 ellipsoids, and the UPS lettering convention used with the International ellipsoid. Other ellipsoid lettering conventions are detailed in DMA TM
8358.1.
(See Figure 3-24.)
1.
UTM.
a.
The first (columnar) letter of the 100,000 meter square identification originates at the 180° meridian with the letter A and increases alphabetically eastward along the equator for three grid zones to cover an area of 18°. The 100,000-meter columns, including partial columns at grid zone junctions, are lettered from " A" to "Z" omitting "I" and "O". This alphabet is repeated every 18° eastward around the earth.
b. The second (linear) letter of the 100,000 meter square identification is lettered from "A" to "V", omitting "I" and "O", from south to north covering an area of 2,000,000 meters and is then repeated northward. In odd numbered grid zones, it originates at the equator increasing alphabetically north. In even numbered grid zones, the second letter

originates 500,000 meters south of the equator increasing alphabetically north.
DRAFT
Therefore, in odd numbered grid zones, the second letter of the 100,000-meter square identification is
Figure 3-24 Military Grid Reference System: 100,00 meter Square Identification Lettering Convention
For the UTM Grid, WGS 84/GRS 80 Ellipsoids.

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"A" along the equator; in even numbered grid zones the second letter is "F" along the equator.
c. Each 6° by 8° square is broken up into 100,000meter squares that occur only once. For example, there is only one square identified by the letters
"WA" inside of the 6° x 8° square of grid zone designation 3N. The only other square in this figure identified by the letters "WA" is in grid zone designation 3Q. It can be seen from this example that unique coordinates can be established for every position within the UTM grid using the MGRS.
2. UPS.
The 100,000-meter square identifiers are the same for both UPS grid zones. The difference between two UPS grid MGRS coordinates with the same 100,000 meter square identifiers is the grid zone designator; "A"/"B" in the south, "Y"/"Z" in the north. Designators "A" and "Y" (western hemisphere) are lettered the same, as are designators
"B" and "Z" (eastern hemisphere). The north zone only includes that portion of the lettering convention that falls inside of 84° latitude. (See Figure 3-25.)
a.
Western Hemisphere.
The first letter of the
100,000-meter square identifier originates at the intersection of the 80° latitude and 90° W longitude lines. It is lettered alphabetically along the east-west axis from "J" to "Z" with "M", "N", "O", "V", and
"W" omitted.
b.
Eastern Hemisphere.
The first letter of the
100,000 meter square identifier originates at the 0° and 180° meridians. It is lettered alphabetically along the east-west axis from "A" to "R" with "D", "E", "I",
"M", "N" and "O" omitted.
c. The second letter of the 100,000-meter square identifier originates at the intersection of the 80° latitude/ 180° longitude lines. It is lettered alphabetically from "A" to "Z" with "I" and "O" omitted. d. MGRS Grid Coordinates.
1. The easting and northing coordinates used with the MGRS are the same as the grid coordinates used with UTM/UPS with the following modifications:
a. For UTM grid MGRS coordinates, delete the first digit (100,000 meters) from the easting and the first two digits (1,100,000 meters) from the northing of the UTM grid coordinates. Add the grid zone number, the zone designator, and the 100,000-meter square identifier at the front of the coordinates.
b. For UPS grid MGRS coordinates, delete the first two digits (1,100,000 meters) from both the easting and northing UPS grid coordinates. Add the zone designator and the 100,000-meter square identifier at the front of the coordinates.
2. The entire MGRS grid coordinate is written as one entity without parenthesis, dashes, or decimals.
Examples:
3Q indicates location within a 6° x 8°
3QXV indicates location to within 100,000m
3QXV41 indicates location to within 10,000m
3QXV4312 indicates location to within 1,000m
3QXV432123 indicates location to within 100m
3QXV43211234 indicates location to within 10m
3QXY4321012345 indicates location to within 1m
a. General.
Many grid systems were developed by individual nations which cover only that nation or a region surrounding that nation. In most cases, no direct relationship exists between local grid systems; the same as no direct relationship exists between the state plane grid systems of the US states. b. Names.
Non-Standard grids are generally named for the nation or region they cover and will normally contain the term Grid, Zone, or Belt (i.e. Ceylon Belt,
Madagascar Grid, and India Zone I).
1. A Grid covers a relatively small area. Its limits consist of combinations of meridians, parallels, rhumb lines, or grid lines.
2. A Zone is usually wide in longitude and narrow in latitude. Its limits consist of meridians and parallels.
3. A Belt is usually wide in latitude and narrow in longitude.

DRAFT
Figure 3-25 100,000 Meter Square Identification: UPS Grid, International Ellipsoid
The World Geodetic Reference System
(GEOREF) is an alphanumeric system for reporting

DRAFT positions based on geodetic coordinates. It is a worldwide position reference system that can be used with any map or chart graduated in latitude and longitude, regardless of the map projection. The primary use of the GEOREF is for inter-service and inter-allied positioning and reporting of aircraft and air targets.
a. When operating in an area that is mapped in a grid system other than UTM and UPS, it may become necessary to "define" the grid system. Defining the grid system is basically orienting a fire support system or survey system to measure or establish azimuths, distances, and elevations from a different origin than it is programmed for. Most current software versions do not allow this option; however, if the option is available, the following information is necessary:
Operational Ellipsoid
Ellipsoid Parameters (a, b, 1/ f )
Scale Factor (at the origin) for the projection
Latitude of the origin
Longitude of the origin
Unit (i.e. meters, feet, yards, chains, rods)
False easting of the origin
False northing of the origin b.
Figure 3-26 lists the needed information for several common non-standard grids as published in
Table 6 of DMA TM 8358.1.
c. Figure 3-27 lists the needed information for several common non-standard grids not published in
DMA TM 8358.1.

DRAFT
Figure 3-26 Specifications for Secondary Grids listed in Table 6 DMA TM 8358.1

DRAFT
Figure 3-27 Specifications for Secondary Grids not listed in Table 6 DMA TM 8358.1