Figure 7-41.—Gaphical method to locate angular mistake ina closed traverse (see angle C).107°42' along the way. You should look for an angle ofabout this size in the traverse.Suppose that in a four-sided traverse, the differencebetween the sum of the R-deflection angles and the sumof the L-deflection angles comes to 180°. For afour-sided traverse, this difference should be 360°. Thelarger difference suggests that you have given one of theangles a wrong direction. Look for an angle measuringabout half the error of closure (in this case, measuringhalf of 180°, or 90°), and see whether you may havegiven this angle the wrong direction.If you have not dropped an angle, a large interior-angle error of closure probably means a large mistakein measuring or in recording the measuring of one of theangles. You may be able to locate the doubtful angle byplotting the traverse from the measured angles. ‘Thendraw in the line of the linear error of closure and erect aperpendicular bisector from this line. The bisector maypoint to the dubious angle.For example: In figure 7-41, all the bearings arecorrect except the bearing of CD, which should beS15°31'W for closure, but inadvertently you made amistake and have S05°31'W. Because of this error, thetraverse fails to close by the length of the dotted line AA'.Figure 7-42.—Graphical method to locate angular mistake ina closed traverse (see angle A).A perpendicular bisector from AA' points directly at thefaulty angle C.If a perpendicular bisector from the line of linearerror of closure does not point at any angle, the faultyangle may lie at the point of the beginning of thetraverse. In figure 7-42, the bearings of all lines arecorrect for closure except that of the initial line AB. LineAB should be N29°09'E for closure but was plottedN16°09'E. A perpendicular from AA' does not point atany angle in the traverse.OUTSIZED LATITUDE AND/OR DEPAR-TURE ERROR OF CLOSURE.— When both thelatitudes and departures fail to close by large amounts,there is probably a mistake in an angle or a distance.When one closure is satisfactory and the other is not, acomputational mistake is probably the cause of theoutsized closure error.OUTSIZED LINEAR ERROR OF CLO-SURE.— When an angular error of closure is withinallowable limits and there is an outsized linear error ofclosure, you should check for mistakes as follows:1. Ascertain that you have not dropped a traverseline.2. Ascertain that each latitude and departure is inthe correct column.7-28

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