disturbed). Last is the STRENGTH OF INTER-SECTION, which generally means that the anglebetween two tie lines should be as close to 90° aspossible. The more acute or obtuse the angle isbetween tie lines, the less accurate the location ofthe point defined by their intersection.IDENTIFYING PARTY PERSONNELA typical transit-tape survey party containstwo chainmen, a transitman, a recorder(sometimes the transitman or party chief doublesas recorder), a party chief (who may serve as eitherinstrumentman or recorder, or both), and axmen,if needed. The transitman carries, sets up, andoperates the transit; the chainmen do the samewith the tapes and the marking equipment.When the transitman turns an angle, he callsout the identity and size of the angle to therecorder, as “Deflection angle AB to BC, 75°16´,right.” The recorder repeats this, then makes theentry. Similarly, the head chainman calls out theidentity and size of a linear distance, as “B to C,265.72 ft,” then the recorder repeats this back andmakes the entry at that time. If the transitmancloses the horizon around a point, he calls out,“Closing angle, such and such.” The recorderrepeats this and then adds the closing angle to theoriginal angle. If the sum of the angles doesn’tcome close to 360°, the recorder notifies theparty chief.The party chief is in complete charge of theparty and makes all the significant decisions, suchas the stations to be marked on the traverse.ATTAINING THE PRESCRIBEDORDER OF PRECISIONThe important distinction between accuracyand precision in surveying is explained as follows:l Accuracy denotes the degree of conformitywith a standard. It relates to the quality of a resultand is distinguished from precision, which relatesto the quality of the operation by which the resultis obtained.The accuracy attained by field surveys is theproduct of the instructions or specifications to befollowed in doing the work and the precision infollowing those instructions.For example, the “accuracy of a surveyor’stape” means the degree to which an interval of100 ft, as measured on the tape, actually agreeswith the exact interval of a standard 100-ft tape.If a tape indicates 100 ft when the interval itmeasures is only 99.97 ft, the tape contains aninaccuracy of 0.03 ft for every 100 ft measured.The accuracy of this particular tape, expressed asa fraction, is 0.03/100, or approximately 1/3,300.l Precision denotes degree of refinement inthe performance of an operation or in the state-ment of a result. It relates to the quality ofexecution and is distinguished from accuracy thatrelates to the quality of the result. The termprecision not only applies to the fidelity ofperforming the necessary operations but, bycustom, has been applied to methods and instru-ments used in obtaining results of a high orderof accuracy. Precision is exemplified by thenumber of decimal places to which a computationis carried and a result stated. In a general way,the accuracy of a result should determine theprecision of its expression. Precision will not havesignificance unless accuracy is also obtained.If you measure a linear distance with a tapegraduated in feet that are subdivided into tenths,you can read (without estimation) only to thenearest tenth (0.1) of a foot. But with a tapegraduated to hundredths of a foot, you candirectly read distances measured to the nearesthundredth (0.01) of a foot. The apparent nearnessof the second tape will be greater; that is, thesecond tape will have a higher precision.Completely precise measurement is impossiblein the nature of things. There is always a built-inor inherent error, amounting to the size of thesmallest graduation. Precision for the first tapeabove, expressed as a fraction, is 0.1/100 or1/1,000 and for the second tape, 1/10,000.Precision in measurements is usually expressedin a fractional form with unity as the numerator,indicating the allowable error within a certain limitas indicated by the denominator, such as 1/500.In this case, you are allowed a maximum errorof 1 unit per 500 units measured. If your unit ofmeasure is in feet, you are allowed 1 ft for every500 ft.In general, any survey has to be carried outaccurately, meaning that errors and mistakes haveto be avoided. The precision of a survey, however,depends upon the order of precision that is eitherspecified or is implied from the nature of thesurvey.The various orders of precision are absolute,not relative, in meaning. Federal agencies controlsurveys. They are generally classified into fourorders of precision; namely, FIRST ORDER,SECOND ORDER, THIRD ORDER, and13-21

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