Taping Taping

Taping (Field Process) The line to be taped should be marked at both ends Keeps measurement on line Rear chain person should keep the head chain person on line 1’ of line error/100’ = 0.01’ error in length Applying Tension Rear chainman is anchor and should hold 100’ mark over point Tension is applied by head chain person – normally 12 to 30 pounds of pull Tapes are standardized at 12 lbs., but greater is utilized to compensate for sag

Taping (Field Process) Plumbing One end of tape is raised to maintain a horizontal measuring plane. ONLY one end is elevated This allows measurements to be made on uneven ground If a high spot exists in center, “break” tape by measuring to the top and then move forward to complete the distance

Slope Measurements: Generally, measurements are made horizontally, but on even, often man-made slopes the distance can be measured directly on the slope, but the vertical or zenith angle must be obtained. Horizontal Distance = sin Zenith Angle X Slope Distance Horizontal Distance = cos Vertical Angle X Slope Distance

Stationing: Starting point is 0+00 and each 100’ is one station 700’ from starting point is Station 7+00 If distance is 857.23’ from starting point, it is expressed as Station 8+57.23

Taping Error: Instrumental Error – a tape may have different length due to defect in manufacture or repair or as the result of kinks Natural Error – length of tape varies from normal due to temperature, wind and weight of tape (sag) Personal Error – tape person may be careless in setting pins, reading the tape, or manipulating the equipment Instrumental and natural error can be corrected mathematically, but personal error can only be corrected by remeasure. When a tape is obtained, it should either be standardized or checked against a standard. Tapes standardized at National Bureau of Standards in Maryland Standardized at 68 degrees F and 12 lbs. tension fully supported.

Tape Error Correction: Measuring between two existing points: If a tape is long, the distance will be short, thus any correction must be added If tape is short, the distance will be long, thus any correction must be subtracted If you are setting or establishing a point, the above rule is reversed. Generally can correct for tape length, temperature, tension, and sag, but tension and sag are negated by increasing tension to approximately 25 – 30 lbs.

Error in Taping: Tape Length: Correction per foot = Error in 100’/100’ If tape was assumed to be 100.00’ but when standardized was found to be 100.02’ after distance measured at 565.75’ then: Correction =(100.02-100.00)/100.00 = 0.0002’ error/ft 565.75’ X .0002’/’ = 0.11’ correction and based upon rule, must be added, thus true distance = 565.86’ If tape had been 99.98’ then correction would be subtracted and true distance would be 565.64’