pole and shifting his body weight until the correcttension is read on the scale. This position can beheld steadily and comfortably for a comparativelylong time.Measuring distances less than a full tape lengthrequires the use of the clamp handle (or “scissorsclamp”), which is attached to the tape at someconvenient point along its length. The handlepermits a firm hold on the tape and furnishes aconvenient attachment for a spring balance. Whenproperly used, the handle will prevent kinking ofthe tape.READING THE TAPE.— A chain tape maybe either a PLUS (or ADD) tape or a MINUS (orSUBTRACT) tape. On a plus tape, the end foot,graduated in subdivisions, is an extra foot, lyingoutside the 0-ft mark on the tape and graduatedAWAY FROM the 0-ft mark. On a minus tape,the end foot, graduated in subdivisions, is the footlying between the 0-ft mark and 1-ft mark andgraduated AWAY FROM the 0-ft mark andTOWARD the 1-ft mark. As will be seen, thisdifference is significant when a distance of lessthan a full tape length is being measured.Suppose that you are measuring the distancebetween point A and point B with a 100-ft tape,and the distance is less than 100 ft. Suppose thatyou are the head chainman. To start off, you andthe rear chainman are both at point A. You walkaway from point A with the zero-foot end of thetape. Because this is a plus tape, the tape has anextra foot beyond the zero-foot end, and this footis subdivided in hundredths of a foot, readingfrom the zero.You set the zero on point B, or plumb it overpoint B; then call out, “Take a foot!” When therear chainman hears this, he pulls back the firsteven-foot graduation between A and B to pointA, or plumbs it over point A. Let’s say this is the34-ft graduation, The rear chainman calls out,“Thirty-four!”You now read the subdivided end-foot gradua-tion that is on or over point B. Let’s say it is the0.82-ft graduation. You call out, “Point eighttwo!‘’ The rear chainman rechecks the even-footgraduation on point A and calls out, “Thirty-fourpoint eight two!”As you can see, yoursubdivided-foot reading is added to his even-footreading; hence, the expression “plus” tape.Suppose now that you are measuring the samedistance between the same points, but using a“minus” tape; that is, a tape on which thesubdivided end-foot lies between the zero-foot and1-ft graduations. This time when you walk awaywith the zero-foot end, you set the 1-ft graduationon point B and call out, “Take a foot!” Whenhe hears this, the rear chainman again hauls backthe first even-foot graduation between A and Bto point A—but this time this will be the 35-ftgraduation. So the rear chainman sings out,“Thirty-five!” When you hear this, you read thesubdivided-foot graduation on point B. This timethis will be 0.18-ft graduation, so you call out,“Minus point one eight!” The rear chainmanmentally subtracts 0.18-ft from 35.00 ft and callsout, “Thirty-four point eight two!” When youare also acting as the recorder, recheck thesubtraction before you record the distance in thefield notebook.GIVING A LINE.— The range pole is set online slightly behind the point toward which thetaping will proceed. Line may be given (that is,the person with the range pole may be guided orsignaled onto the line) by “eyeball” (that is, byeye-observation alignment by the rear chainmanor someone else at the point from which chainingis proceeding) or by instrument.Slope ChainingThe methods used in slope chaining arebasically the same as in chaining on level ground.There are some differences, however, as follows:In slope chaining, the tape is held along the slopeof the ground, the slope distance is measured, andthe slope distance is converted, by computation,to horizontal distance. The slope angle isusually measured with an Abney hand level andclinometer; however, for precise measurement, itis measured with a transit.In using the clinometer, you take the slopeangle along a line parallel to the slope of the groundor along the tape that is held taut and parallel tothe slope of the ground. To use the clinometer,you sight on an object that is usually a point ona pole approximately equal to your height ofinstrument (HI); that is, the vertical distance fromthe ground to the center (horizontal axis) of thesight tube. While sighting the object, you rotatethe level tube about the axis of vertical arc untilthe cross hairs bisect the bubble as you lookthrough the eyepiece. Then, you read either theslope angle or percentage on the vertical arc andrecord it along with the slope distance measure-ment. The horizontal distance is computed, or inother words, the tape correction is applied.If the station points are being marked, thecorrections to the slope distances are applied asthe chaining progresses. These correct ions arecomputed either mentally, by calculator, or byusing a table.12-13

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