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surveying iii (topographic and geodetic surveys) - Modern Prepper

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If the azimuth error does not fall within the AEC, surveyors must reobserve the station angles of thetraverse in the field.o. Azimuth Corrections. Before determining a correction, surveyors compute the actual azimutherror. The azimuth error is obtained by subtracting the computed closing azimuth from the knownclosing azimuth. This difference provides the angular error with the appropriate sign. By reversing thissign, the azimuth correction (with the appropriate sign) is obtained. If the azimuth correction fallswithin allowable limits, surveyors may compute the error <strong>and</strong> the correction.(1) Traverse adjustment is based on the assumption that errors have accumulated gradually <strong>and</strong>systematically throughout the traverse. The azimuth correction is applied accordingly. The correction isdistributed systematically among the angles of the traverse.(2) After the angles are adjusted, surveyors compute the adjusted azimuth of each leg by usingthe starting azimuth <strong>and</strong> the adjusted angles at each traverse station. Surveyors should compute theadjusted azimuth throughout the entire traverse <strong>and</strong> check against the correct azimuth to the closingazimuth mark before beginning any further traverse computations.p. Azimuth-Bearing Angle Relationship. The trigonometric functions (sine, cosine, tangent, <strong>and</strong> soon) of the azimuth <strong>and</strong> the bearing are numerically the same. Surveyors may use either the azimuth orthe bearing to compute the traverse. The choice depends upon the computer <strong>and</strong> the availableequipment.q. Azimuth <strong>and</strong> Bearing. If a calculator with angular functions is available, the use of the azimuthis easier since it eliminates the need to compute the bearing. If the functions must be determined fromtables, it is necessary to first compute the bearing angles since the tabulation of functions is normallypublished for angles of 0° to 90°. The bearing of a line is the acute angle (less than 90) formed by theline in question <strong>and</strong> the north-south line through the occupied point. This illustrates the relationshipbetween the azimuth of a line <strong>and</strong> its bearing.r. Quadrants. The manner for computing bearing angles from a given azimuth depends on thequadrant in which the azimuth lies. When the azimuth is in the first quadrant (0° to 90°), the bearing isequal to the azimuth. When the azimuth is in the second quadrant (90° to 180°), the bearing is equal to180° minus the azimuth. When the azimuth is in the third quadrant (180° to 270°), the bearing is equalto the azimuth, minus 180°. When the azimuth is in the fourth quadrant (270° to 360°), the bearing isequal to 360° minus the azimuth. Since the numerical values of the bearings repeat in each quadrant,surveyors must label them <strong>and</strong> indicate into which quadrant they fall. The label must indicate whetherthe bearing angle is measured from the north or south line <strong>and</strong> whether it is east or west of that line. For3-31 EN0593

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