The magnetic compass is the most commonlyused and simplest instrument for measuringdirections and angles in the field. This instrumenthas a variety of both civilian and militaryapplications. The LENSATIC COMPASS (available inyour Table of Allowance) is most commonly used forSEABEE compass courses, for map orientation, andfor angle direction during mortar and field artilleryfires.In addition to this type of compass, there areseveral others used exclusively for field surveys. TheENGINEER’S TRANSIT COMPASS, located betweenthe standards on the upper plate, is graduated from0° through 360° for measuring azimuths, and inquadrants of 90° for measuring bearings (fig. 11-4).Notice in figure 11-4 that the east and west markingsare reversed. This permits direct reading of themagnetic direction.The compass shown in figure 11-5 is commonlycalled the BRUNTON POCKET TRANSIT. Thisinstrument is a combination compass and clinometer.It can be mounted on a light tripod or staff, or it maybe cradled in the palm of the hand.Other types of compasses can also be found insome surveying instruments, such as the theodoliteand plane table.Figure 11-4.-Engineer’s transit compass.ENGINEER’S TRANSITA primary survey fieldwork consists ofmeasuring horizontal and vertical angles ordirections and extending straight lines. Theinstruments that can perform these functions haveadditional refinements (built-in) that can be used forother survey operations, such as leveling. Two typesof instruments that fall into this category are theengineer’s transit and the theodolite. In recent years,manufacturing improvements have permitted con-struction of direct-reading theodolites that are soon toreplace the vernier-reading transits. However, inmost SEABEE construction, the engineer’s transit isstill the major surveying instrument.45.742Figure 11-5.-A Brunton pocket transit.11-13
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