A building is an obstacle to

🚧 Understanding Obstacles in Surveying

In chain surveying, obstacles are classified based on the specific activities they obstruct. A building is a classic example of a complete obstruction because it interferes with the two fundamental processes of the survey.

🔬 Detailed Analysis

A building presents a complete barrier to the two primary activities of chain surveying:

• Obstacle to Chaining (Measuring): It is physically impossible to stretch a survey chain or tape directly through a building. This prevents the direct linear measurement between two points on opposite sides.
• Obstacle to Ranging (Sighting): It is also impossible to see from a point on one side of a building to a point on the other. This prevents the direct alignment of intermediate points along a straight survey line.

Because a building blocks both measurement and sighting, it is considered an obstacle to both chaining and ranging.

💡 How to Survey Around Such Obstacles

To overcome an obstacle like a building, surveyors must use indirect methods. For example, they might establish perpendiculars from the main line to bypass the building, or use the random line method. This involves creating a temporary survey line that avoids the building, taking various measurements, and then using geometry (e.g., properties of triangles) to calculate the length and direction of the original, obstructed line.