Engineering Survey I (CE153) Lab Reports

• Tape

• Peg

• Arrow

• Ranging rod

• Hammer

Tape

Linen tapes are constructed from closely woven linen and are varnished to resist moisture.

Peg

Wooden pegs, typically 15 cm in length and 2.5 cm square in section, are used to mark station points or the endpoints of a line on the ground. They are tapered at one end and driven into the ground with a wooden hammer, leaving approximately 4 cm projecting above the ground.

Arrow

Arrows are crafted from tempered steel wire with a 4 mm diameter. One end is bent into a 50 mm diameter ring, and the other end is pointed. The total length of an arrow is 400 mm. Arrows are utilized to count the number of chains when measuring a chain line.

Ranging Rod

Ranging rods are used for ranging, which is the process of straightening a line. These rods are made of seasoned timber or bamboo. The rod is marked in equal 20 cm sections, which are painted alternately in black and white or red and white to ensure visibility from a distance.

Hammer

A hammer is a tool with a weighted head attached to a long handle, swung to deliver an impact to a small area of an object.

Pacing

Pacing is a straightforward and quick method for measuring distances in the field. It is frequently used in conjunction with a sighting or hand compass. By establishing one’s pacing factor, distances can be easily calculated.

Ranging

Ranging is the process of setting up intermediate points along a straight line between two endpoints. This must be completed before a survey line is measured. Ranging can be done through direct observation with the naked eye, a line ranger, or a theodolite. Typically, it is performed by eye with the aid of three ranging rods.

Discrepancy and Precision

A discrepancy is an unexpected or illogical lack of similarity between two or more facts. Precision refers to the quality, condition, or fact of being exact and accurate.

For Linear Measurement of Plain Ground

Two points are established on the ground to define the line for linear distance measurement. Two wooden pegs are fixed, and behind them, two ranging rods are positioned vertically with the aid of a plumb bob. Another ranging rod is placed such that the distance between any two rods is less than 15m. An arrow is placed at the third rod, and this process is repeated until the second endpoint is reached. The positions of the arrows are then used to measure the distance in the backward direction.

For Determination of Pace Factor

1. Two ranging rods are fixed at a distance of 40m.

2. Walk between these rods at a normal pace three times, both in the forward and backward directions.

3. Remember to count the number of steps taken during each walk.

4. Counting should start from the heel, and the ending should be considered accordingly. The pace factor is determined by dividing the total distance traveled by the total number of steps.

Distance Measurement by Tape

Determination of Pacing Factor

Discrepancy = |Total FW – Total BW| = |80.162 – 80.124| = 0.038

Precision = Discrepancy / Mean = 0.038 / 80.143 = 0.00047415 ≈ 1:2109

The measured distance between the two random points was 80.143 m. The pacing factor was determined to be 0.714. The discrepancy and precision for the linear distance measurement in the forward and backward directions were found to be 0.038 and 1:2109, respectively.

Through this surveying practical, we have learned how to range a line using ranging rods and how to calculate a pacing factor.

1. Ranging rods, pegs, and arrows should be kept in a straight line.

2. The distance between ranging rods should not be excessive to avoid errors that may arise from sagging.

3. Readings from the measurement tape should be taken carefully.

• Measuring tape (30m) – 1

• Abney level – 1

• Ranging rods – 4

• Plumb bob – 1

• Marking arrows

• Hammer – 1

• Wooden Pegs – 5

Ranging a Line

When a measuring tape is insufficient to measure an entire allocated distance in one go, the line must be broken down into intermediate points on a straight line. The total distance is then obtained by summing the distances between these intermediate points.

Linear Measurement of Sloping Ground

The horizontal and vertical distance of sloping ground can be measured in two ways:

Direct Method (Stepping Method):

In this method, the slope is ranged with ranging rods. The horizontal and vertical distances are measured directly in steps. The tape is kept horizontal for each step, either by eye judgment or by using a hand level. The horizontal and vertical distances of each step are measured, and the final total horizontal and vertical distances are calculated by summing the individual measurements.

Indirect Method:

In this method, the angle the slope makes with the horizontal is measured using an Abney level, and the slope distance is measured with a measuring tape. Trigonometric relations are then used to determine the horizontal and vertical distances.

a. Direct Method (Stepping)

First, two endpoints were finalized, and pegs were fixed behind the ranging rods at these locations.

The total distance between the pegs was broken into parts, ensuring each part had a relatively uniform slope. A third ranging rod was fixed and made vertical, aligned with the first two. This process was repeated until the entire distance was divided into multiple parts.

The horizontal and vertical distances between these rods were then measured with a measuring tape.

Finally, the same process was repeated for the backward direction to ensure accuracy.

b. Indirect Method (by Abney Level)

Two endpoints were finalized, and ranging rods along with pegs were fixed at these points.

Intermediate points were selected based on the steepness of the ground, ensuring the distance between them did not exceed the length of the tape.

The sloping distance between two intermediate points was measured using a measuring tape, and the corresponding slope angle was measured using an Abney level.

This process was repeated for the backward direction.

Direct Method

Indirect Method

Total vertical distance (avg for forward) = 6.848 m

Total horizontal distance (avg for forward) = 24.142 m

Slope = Vertical / Horizontal = 6.848 / 24.142 = 1:3.525

From this fieldwork, the horizontal and vertical distances from the direct method were found to be 24.331 m and 3.6075 m, respectively.

From this practical, we learned to measure the vertical and horizontal distance of sloping ground. We also learned how to measure a horizontal angle using an Abney level. While measuring horizontal and vertical distances by direct and indirect methods, some error occurred. This error may be due to the instrument or improper handling of the instrument.