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Aircrew Map Conversion Techniques
by CPT John C. White, Military Analyst, CALL

1. DISCUSSION: Maps currently used for both mission planning and flight operations do not give aircrews the necessary detail to fly and fight on an urban environment. Both joint operational graphics (JOG) maps and tactical 1:50,000 scale maps do not provide the necessary detail. Aircrews must have maps that accurately portray the terrain within the city, man-made features in the city, and hazards to flight. Aircrews can use both the JOG and 1:50,000 maps for en route navigation to the city and then transfer to maps that offer greater detail. The Air, Land, Sea Application Center's draft manual, Aviation Urban Operations, provides a technique to convert a civilian city map for use.

2. TTP: Civilian Map Conversion

Units may also convert civilian maps to the military grid reference system (MGRS) using the technique below. There must be enough maps so that both the air and ground units can use them. If military grid coordinates are required for navigation or targeting, the civilian map must be overlaid with the MGRS using the following method:

Determine two known locations (surveyed grid, GPS, or extracted from tactical land map) identifiable on the civilian map. Designate these locations as points #1 and #2.

EXAMPLE: On the Killeen/Ft. Hood, TX residential map, the distance between points #1 and #2 equals 35.7 cm.


M = 35.7 cm

Determine the scale of the map to be used. Express in cm per KM and ratio.

M/H = 35.7 cm / 11.02 KM = 3.24 cm per KM


H/M = 11.02 KM / 35.7 cm = 0.30868


Scale = 1:30,868

Determine the northing and easting differences ("Nm" and "Em") expressed in cm of map distance. Nm = N * (M/H), Em = E * (M/H)

Nm= (5.52) (3.24) = 17.88 cm
Em= (9.45) (3.24)= 30.62 cm

Mark the northing and easting differences (measured in cm) along two adjacent edges of a blank sheet of paper.

Difference Markings

Position the paper on the civilian map with each mark on the paper edges over points #1 and #2. Place a mark on the map at the corner of the paper between the two edges used. This is the grid north reference point. If the points and marks will not line up with the paper lying flat, an error has been made in the previous steps or the map is distorted.

With a pencil and a straight edge, connect both points #1 and #2 to the reference point. Extend these lines through the reference point in each direction. These are the N-S and E-W reference lines.

Based on the known grid locations of points #1 and #2, determine the distance to the nearest whole-numbered grid line.

#1: 0.33 KM from 17 N-S grid line
#2: 0.02 KM from 38 E-W grid line

Determine the map distance to the whole-numbered grid lines.

#1: (0.33)(3.24) = 1.07 cm from N-S reference line
#2: (0.02)(3.24) = 0.06 cm from E-W reference line

With a quality metric ruler, measure the distance from the reference lines in the appropriate direction and draw grid lines parallel to the reference lines. Label these with the whole number grid line value.

  • Measure 1.07 cm west from the N-S reference line, plot at least two points parallel to the reference line, connect the points, and label this line "17".
  • Measure 0.06 cm south from the E-W reference line, plot at least two points parallel to the reference line, connect the points, and label this line "38".

Working in 1KM intervals (M/H) from the labeled grid lines, create a grid pattern on the map or on an overlay. Label the grid lines with the appropriate whole numbers along the margin. Verify that points #1 and #2 map grids correspond with the known positions. Establish a grid pattern originating from the intersection of the initial grid lines with each grid square equaling 3.24 cm on each side. Label the grid lines along the map or overlay edges.

Manufacture a grid protractor with at least 100 meter degree of accuracy (50 meter or 10 meter accuracy preferred, depending on scale). Cut a 5" x 8" card in half lengthwise. Take the halves and overlap them with one oriented horizontally and the other vertically. Align the edges of both cards at a common corner and tape or paste the cards together. Beginning at the apex of the inside right angle described by the two cards, make ten prominent marks, one every 0.324 cm. These represent 100 meter intervals. Label these 1-10. Total distance from the apex to the tenth mark should be exactly 3.24 cm. Halfway between each of the numbered marks, place a smaller mark to define the 50 meter interval.


Validate the accuracy of the grid pattern and protractor. If available, use a third known position, extract the grid using the protractor on the newly prepared map, and compare it with the known grid location. If a significant discrepancy exists, either an error has been made in the preparation process, or the map being used is distorted in relation to the actual terrain (i.e., the map is a hand-drawn tourist-type map without a basis on satellite/aerial imagery or survey data).

btn_tabl.gif 1.21 K
btn_prev.gif 1.18 KAppendix C: Weapon Effects and Employment in an Urban Environment
btn_next.gif 1.18 KAppendix E: Task Summary Sheet

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