MSL101L04 Basic Map Reading SR.pdf lesson 4.pdf

4 20 world geographic reference system georef this is

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4-20. World Geographic Reference System (GEOREF). This is a worldwide position reference system used primarily by the U.S. Air Force. It may be used with a map or chart that has latitude and longitude printed on it. Instructions for using GEOREF data are printed in blue and are found in the margin of aeronautical charts. This system is based upon a division of the earth’s surface into quadrangles of latitude and longitude having a systematic identification code. It is a method of expressing latitude and longitude in a form suitable for rapid reporting and plotting. Figure 4-24 illustrates a sample grid reference box using GEOREF. The GEOREF System uses an identification code that has three main divisions: First division. There are 24 north-south (longitudinal) zones, each 15-degree wide. These zones, starting at 180 degrees and progressing eastward, are lettered A through Z (omitting I and O). The first letter of a GEOREF coordinate identifies the north-south zone in which the point is located. There are 12 east-west (latitudinal) bands, each 15-degrees wide. These bands are lettered A through M (omitting I) northward from the South Pole. The second letter of a GEOREF coordinate identifies the east-west band in which the point is located. The zones and bands divide the earth’s surface into 288 quadrangles, each identified by two letters. Second division. Each 15° quadrangle is further divided into 225 quadrangles of 1 degree each (15-degrees-by-15-degrees). This division is effected by dividing a basic 15-degree quadrangle into 15 north-south zones and 15 east-west bands. The north-south zones are lettered A through Q (omitting I and O) from west to east. The third letter of a GEOREF coordinate identifies the 1-degree north-south zone within a 15-degree quadrangle. The east-west bands are lettered A through Q (I and O omitted) from south to north. The fourth letter of a GEOREF coordinate identifies the 1-degree east-west band within a 15-degree quadrangle. Four letters identify any 1-degree quadrangle in the world.
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Chapter 4 4-28 TC 3-25.26 15 November 2013 Third division. Each of the 1-degree quadrangles is divided into 3,600 1” quadrangles. These 1” quadrangles are formed by dividing the 1-degree quadrangles into 60 1” north- south zones numbered 0 through 59 from west to east, and 60 east-west bands numbered 0 to 59 from south to north. To designate one of the 3,600 1” quadrangles requires four letters and four numbers. The rule READ RIGHT AND UP is always followed. Numbers 1 through 9 are written as 01, 02, and so forth. Each of the 1” quadrangles may be further divided into 10 smaller divisions both north-south and east-west, permitting the identification of 0.1” quadrangles. The GEOREF coordinate for a 0.1”quadrangle consists of four letters and six numbers. (See Figure 4-24.) Figure 4-24. Sample reference using GEOREF P ROTECTION OF M AP C OORDINATES AND L OCATIONS 4-21. A disadvantage of a standard system of location is that if the enemy intercepts a friendly message using the system, they can interpret the message and find our location. This possibility can be eliminated by
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