Fieldwork No

FIELDWORK NO. 2

PROLEM : TAPING OVER SMOOTH AND LEVEL GROUND OBJECTIVE : To determine the horizontal length of a line over smooth and level ground with the tape supported throughout its length. A. INTSTRUMENTS AND ACCESSORIES: 30-m or 100-ft. Steel Tape, Chaining Pins, Range Poles, Pegs or Hubs, Chalk or Marking Crayons, and Spring Scale. B. PROCEDURE: 1. Using hubs mark both ends of the line (150 to 300 m long) to be measured. Place a range pole behind each point and also establish intermediate points along the line to ensure unobstructed sight line. If the point to be mark is on a pavement, use chalk or marking crayons. Designate these end points as A and B. 2. The rear tapeman with one pin stations himself at the point of beginning and the head tapeman takes the zero end of the tape and advances toward the other end of the line to be measured. 3. When the head tapeman has gone nearly a full tape length, the rear tapeman calls “tape” to stop the head tapeman. The rear tapeman then holds the 30-m (or 100-ft.) mark at the starting point and aligns the other end of the tape held by the head tapeman on the range pole set behind the end point or on any of the intermediate points earlier established along the line. 4. With the 30-m (100-ft.) mark at the starting point, and the head tapeman aligned, the rear tapeman calls “all right”. The head tapeman then pulls the tape taut and sticks a chaining pin in the ground to mark the 0-m (0-ft.) end of the tape. If the measurement is done on pavement, a chalk of marking crayon is used to mark the end of the tape. 5. The rear tapeman picks up his chaining pin and the head tapeman pulls the tape forward and the process is repeated for the next full tape length. 6. When the end of the line is almost reached and the last full tape length has been measured, the remaining partial length is then measured. The rear tapeman holds the tape until he has a full meter (or foot) mark at this chaining pin while the head tapeman pulls the tape taut and takes note of the fractional measurement read from the tape end. 7. After the measurement of the whole line is completed, a second measurement should be made along the opposite direction. The mean of the two measurements is taken as the most probable value of the length of the line. 8. Tabulate observed and computed values accordingly. Refer to the accompanying sample format for the tabulation of data.

TRIAL LINE LENGTH DIFFERENCE 1

AB

MEAN

RELATIVE PRECISSION

2

BA

C. COMPUTATIONS: 1. The mean length of the measured line is determined by adding the two measurements and dividing the sum by two. 2. The discrepancy for the measurement is the difference between the first measurement and the second measurement. 3. The relative precision of the measurement is determined by dividing the discrepancy by the mean length, where the numerator is reduced to unity or 1. Relative precision is expressed in fractional form and the numerator is rounded to the nearest hundredth. D. REMARKS, HINTS, AND PRECAUTIONS: 1. The hub is set at each end of the designated line, and a range pole is set about a meter beyond the far hub to serve as guide during taping. A 2” x 2” piece of lumber with a nail in the middle is used for this purpose and embedded securely into the ground. 2. Prior to measurement, the tape should first be calibrated 3. As a rough check, the designated line should also be measured by pacing. 4. During measurement the tape should be supported throughout the entire length and a required pull (approximately 4 to 7 kg) applied at the ends of the tape to avoid inconsistent errors. 5. During the lining-in process, the head tapeman is in a kneeling position to one side and facing the line so that he can hold the tape steady and allow the rear tapeman to have a clear view of the range pole marking the distant point. 6. As the rear tapeman leaves after each full tape length is measured, a pin is pulled out of the ground. There is always one pin in the ground, and the number of pins held by the rear tapeman at any time indicates the number of full tape lengths measured from the point of beginning to the pin in the ground. 7. A steady and firm pull is made on one end of the tape if the leather thong at the end of the tape is wrapped around the hand or by holding on to a chaining pin slipped through the eye at the end of the tape, or by using the tape clamp. 8. The tape may be held between the fleshy portion of the fingers and that of the palm. Enough friction is applied to sustain the required pull without causing injury or discomfort to the tapeman. 9. The acceptable precision should be at least 1/1000. If this not attained the measurement should be repeated.