easy. If you do not find the adjacent station easily,you should observe an astronomic azimuth toorient the starting line, and then continue thetraverse. Any existing control near the traverseline should be tied in to the new work.PERFORMING LINEARMEASUREMENTSAs traversing progresses, linear measurementsare conducted to determine the distance betweenstations or points. Generally, the required traverseaccuracy will determine the type of equipment andthe method of measuring the distance. For thelower orders, a single taped distance is sufficient.However, as the order of accuracy gets higher,DOUBLE TAPING (once each way) is required.Ordinary steel tapes must be compared to anInvar or Lovar tape at specified intervals. For thehighest accuracy, electronic distance-measuringdevices (EDM) are used to measure lineardistances. Linear measurements may also be madeby indirect methods, using an angle measuringinstrument, like the transit or theodolite withstadia. When the distances are determined bystadia readings, the vertical angles are read andused to convert slope distances to horizontaldistances.If double taping or chaining is required, followthese procedures:1. Follow a direct line between stations, usinga guide, such as a transit and a range pole, foralignment. Start measuring from the occupiedstation, keeping the front end of the tape alignedwith the forward station.2. Start back from the forward station,using the same alignment but not the sametaping points. The second measurement must beindependent of the first.3. Compare the two distances, and if withinaccuracy requirements, the distance is accepted.If the two measurements disagree by more thanthe allowable amount, retape the distance.4. Proceed to the next line measurement, andcontinue double taping until the tie-in controlpoint is reached.PERFORMING ANGULARMEASUREMENTHorizontal angles formed by the lines of eachtraverse station determine the relative directionsof the traverse lines. These angles are measuredusing a transit or a theodolite, or determinedgraphically with a plane table and alidade. In atraverse, three traverse stations are significant: theREAR STATION, the OCCUPIED STATION,and the FORWARD STATION (fig. 13-30). Therear station is that station from which the crewperforming the traverse has just moved, or it isa point, the azimuth to which is known. Theoccupied station is the station at which the crewis now located and over which the surveyinginstrument is set. The forward station is the nextstation in succession and constitutes the immediatedestination of the crew. The stations arenumbered consecutively starting at Number 1 andcontinuing throughout the traverse. In additionto the number of station, an abbreviationindicating the type of traverse is oftentimesFigure 13-30.-Traverse stations and angles.13-29
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