Module 5. Taping-Measurement of Horizontal Distance PDF

Preview

Summary

Download Module 5. Taping-Measurement of Horizontal Distance PDF

Description

PANGASINAN STATE UNIVERSITY – URDANETA CAMPUS Module in CE 211-ENGINEERING SURVEYS

Module No. 05

horizontal length between plumb lines at the points.

TOPIC OUTLINE

COMPOSITION PARTY

A. Composition of Taping Party a. Head Tapeman b. Recorder c. Flagman d. Rear Tapeman B. The Procedure of Taping a. Aligning the Tape b. Stretching the Tape c. Plumbing d. Marking Full Tape Lengths e. Tallying Taped Measurements f. Measuring Fractional Lengths C. Breaking Tape D. Slope Taping E. Corrections in Taping F. Correction due to incorrect tape length

OF

TAPING

Taping is the process of directly measuring distances with the use of graduated tape, When the measurement is undertaken in fairly level ground in an open field, the taping party usually consists of the following individuals. 1. Head Tapeman. The person responsible for the accuracy and speed of all linear measurements with the tape. He determined and directs the marking of points or stations, orders the clearing out of obstructions along lines to the measured, and is the person who carries the zero end of the tape ahead. 2. Recorder. Keeps a record of all measurements, sketches and observations taken during the process of measurement. 3. Flagman. The person whose duty is to hold the range pole (or flagpole) at selected points. He also helps the tapeman in making measurements and assists in clearing out obstructions along the line to be measured. 4. Rear Tapeman. The person whose duty is to assist the head tapeman during a taping operation. He is the one who holds the 30-m end or any intermediate meter mark of the tape during a measurement.

LEARNING OBJECTIVES

1. To be able to learn and study the composition, procedure, aligning, stretching, marking and measuring horizontal distances in surveying. OVERVIEW

One of the most important operations in surveying is measurement of horizontal distance between two points. If the points are at different elevations, the distance is the

THE PROCEDURE OF TAPING 1

PANGASINAN STATE UNIVERSITY – URDANETA CAMPUS Module in CE 211-ENGINEERING SURVEYS

Module No. 05

head tapeman, after being lined-in properly, exerts the required pull on the tape, notes the zero end and sets a pin beside it. The chaining pin may be set vertically in the ground or given a slant at right angles to the line measured.If the head tapeman is satisfied that the measurement was done accordingly, he signalsthat the point marked is acceptable. 5. Tallying Taped Measurements. At the initial point the rear tapeman holds one pin and the head tapeman begins with ten pins carried on his steel ring. This is the reason why a set of eleven pins is normally used during taping operations. The first pin which the rear tapeman holds indicates that one tape length has already been measured, and the total number of pins in his possession indicates the total number of full tape lengths that have so far been measured. 6. Measuring Fractional Lengths. When the last segment of the line is to be measured, this will often be a measurement which will consist of a fractional tape length. Upon reaching the end of a line, the head tapeman comes to a halt and the rear tapeman positions himself at the last pin set. The rear tapeman holds the tape in such a manner that a whole meter mark is aligned with and opposite the pin. The terminal point should fall within the end meter mark of the tape which is subdivided into smaller

The usual procedure in the taping of distances will involve the process of aligning the tape, stretching it, plumbing selected tape marks, marking and recording tape lengths. 1. Aligning the tape. When a line is to be measured, both ends must first be marked. It may also be necessary to establish a few intermediate points to serve as guides in obtaining a straight line. 2. Stretching the Tape. With the 30-m mark held at the initial point, and the head tapeman aligned, the rear tapeman calls out “all right” or “OK”. The head tapeman takes his position just to the left (or right) of the line, kneels, and pulls the tape taut. The tape may be held between the fingers and the palm. He then sticks a chaining pin into the ground to mark the zerometer end of the tape. When the head tapeman sets his pin, the rear tapeman should be holding his end of the tape precisely on the mark. 3. Plumbing. When the ground is covered by obstacles, weeds, low brush, and irregularities in the ground surface, it will difficult or impossible to lay the tape on the ground during measurement. Both ends of the tape should instead be held above ground and in a horizontal position. 4. Marking Full Tape Lengths. When a full tape length measured the rear tapeman holds his end of the tape opposite the pin earlier set on the ground. The 2

PANGASINAN STATE UNIVERSITY – URDANETA CAMPUS Module in CE 211-ENGINEERING SURVEYS

Module No. 05

In Fig., if the angle ∝ is known, the horizontal distance between points A and B can be computed from the relation

graduations, usually in centimeters.

BREAKING TAPE

D = s cos∝ ………………….……….……Eq.(1) Where d is the horizontal distance between the two points, s is the measured slope length between the points, and ∝ is the angle of inclination from the horizontal.

In measuring down a slope, the zero end of the tape is carried ahead. When the full tape length is stretched out, the head tapeman lays the tape on the ground and returns ups the slope to pick up the tape at some meter mark which will allow him to hold horizontally a convenient length between himself and the rear tapeman. The tape is usually held at about the level of the waist or chest. After the head tapeman plumbs his end of the tape and marks its projection on the ground, he drops the tape and proceeds down the slope to hold the tape horizontally at some other convenient meter mark.

If the difference in elevation, h , between the ends of the line (or tape) is known, the horizontal distance is computed using the following expression derived from the pythagorean theorem. d=√𝒔𝟐 − 𝒉𝟐 ………………..………………Eq.(2) CORRECTIONS IN TAPING

Taping operations could be either be of the following: taping to determine an unknown length or taping for the purpose of laying out a required or specified length. Regardless of which of these two categories is involved, there are some corrections which are applied to the original measurements to determine the correct and more accurate length. Corrections to taping are applied by the use of the following rules:

SLOPE TAPING

Taped measurements may be made directly along the slopes when the ground is of uniform inclination and fairly smooth, rather than break tape every few meters. This very practical method is generally preferred since measurements could be made quickly and more accurately than horizontal measurements.

1st RULE: When a line is measured with a tape that is “too long”, the corrections are applied to the observed length by adding. 2nd RULE: When a specified or required length is to be laid out with a tape that is “too long”, the corrections are subtracted from the known 3...