9781422287859

12 Surviving with Navigation & Signaling

Soldiers must be aware of these variations to take accurate bearings. If they have an adjustable compass and know how much it, and their map, differs from true north, they can match them all up to take accurate bearings. Using maps The best maps to use are those produced by the U.S. Geographical Survey. Other popular maps are produced by Rand McNally and Hallwag. They are available in a variety of scales, and troops choose the one that best fits their requirements. The most important skill is the ability to translate the lines on a map into the actual shape of the terrain. Grids Grids on maps usually form squares to help soldiers assess distances. They can find a position on a map by quoting grid coordinates. The reference is usually given as a six-digit number. To give readings, they always bear in mind that grid references follow the rule “along the corridor, up the stairs.” The first three coordinates are taken from the bottom or top margin, the second three numbers from the left or right margin. (Troops must mentally divide each map square into tenths to pinpoint the location.) The map reference for the spot on the map shown is therefore 205558. Symbols A knowledge of map symbols, combined with grids, scale, and distance, give enough information for the soldier to be able to locate two points on a map and work out how long it will take to travel between them.