solve the problems whenever obstacles occur in chain survey

Summary

This educational script teaches surveying techniques to overcome obstacles in chain surveying. It covers methods for calculating distances and positions when physical barriers prevent direct ranging or chaining. The script explains using intermediate stations, triangulation, and similar triangles to measure distances when faced with hills, rivers, or buildings. It also details how to measure distances when both chaining and ranging are obstructed by running perpendicular lines and measuring the joining line's length.

Takeaways

• 📏 Chaining and ranging are fundamental surveying methods used to determine distances and positions of objects on the ground.
• 🚫 Obstacles on the ground can hinder the free use of chaining and ranging techniques.
• 🔄 To overcome obstacles to ranging, use chaining or triangulation to measure distances indirectly.
• 🏞️ When a hill obstructs direct ranging, set intermediate stations and chain from one to the next to calculate the total distance.
• 📐 In the presence of a large rock, form a right-angled triangle and use the Pythagorean theorem to calculate the hypotenuse.
• 🌊 If a river blocks chaining but not ranging, use a cross staff to establish similar triangles and calculate the distance between points.
• 🏢 When a building obstructs both chaining and ranging, use perpendicular lines and a cross staff to measure the distance directly.
• ⛓️ For obstacles to ranging but not chaining, stepping or triangulation with a chain can be used to find distances.
• 📐️ To calculate distances when only chaining is possible, use the ratio of corresponding sides of similar triangles.
• 🏗️ When both chaining and ranging are obstructed, mark points to create perpendicular lines before and after the obstacle, then join and measure the line.
• 🛠️ This module teaches how to solve problems when obstacles occur in chain survey, providing methods for different types of obstacles.

Q & A

What are the basic methods mentioned for finding distances and relative positions of objects on the ground?

The basic methods mentioned for finding distances and relative positions of objects on the ground are chaining and ranging.

What is the primary challenge when obstacles are present on the ground?

The primary challenge when obstacles are present is that they may prevent the free execution of ranging or chaining, which are necessary for measuring distances and positions.

How can you measure the horizontal distance between two points separated by a hill?

To measure the horizontal distance between two points separated by a hill, you can set intermediate stations (like C and D) on either side of the hill, chain from A to C and from D to B, and then add the horizontal distances of AC and DB to obtain the total distance between A and B.

What is the significance of a right-angled triangle in the context of overcoming obstacles with chaining?

In the context of overcoming obstacles with chaining, a right-angled triangle is significant because it allows you to use the Pythagorean theorem to calculate the length of the hypotenuse (the distance between two points) when the lengths of the other two sides are known.

How do you calculate the distance between two points separated by a river when chaining is obstructed?

When chaining is obstructed by a river, you can use the method of setting up similar triangles by taking perpendicular offsets and using the cross staff. By equating the ratio of corresponding sides of these triangles, you can calculate the distance between the two points.

What is the strategy for measuring distance when an obstacle prevents both ranging and chaining?

When an obstacle prevents both ranging and chaining, you can mark points to run two perpendicular lines of equal length, one before and one after the obstacle, then join those points and measure the length of the joining line.

Why is it important to set intermediate stations when an obstacle like a hill obstructs ranging?

Intermediate stations are important because they allow you to bypass the obstacle by chaining to these stations and then summing the distances to calculate the total distance between the original points.

How does the Pythagorean theorem help in surveying when obstacles are present?

The Pythagorean theorem helps in surveying by allowing the calculation of the hypotenuse of a right-angled triangle, which represents the distance between two points, when the lengths of the other two sides (which can be measured around the obstacle) are known.

What role does the cross staff play in surveying when obstacles are present?

The cross staff plays a crucial role in surveying by helping to establish perpendicular offsets and ensuring that measurements are made at right angles, which is essential for setting up similar triangles and for measuring distances accurately around obstacles.

Why is it necessary to mark points beyond the obstacle when measuring distances?

Marking points beyond the obstacle ensures that the entire distance between the two points of interest is accounted for, especially when the obstacle prevents direct measurement, and it allows for the accurate calculation of the total distance by considering the lengths of the segments on either side of the obstacle.