1.2. Basic Principles of Surveying

This is a fundamental and most important principle of surveying. Almost all survey works are required to follow this principle, particularly larger (whole) areas. In working from whole to part, a large (whole) area is divided into smaller parts by providing horizontal controls throughout the area. The smallest part of the area will consist of a triangle. If surveying is done without dividing into smaller parts, any error occurred in a part gets magnified at the end of entire survey work, and the error becomes large which can't be accepted for a good work. Whereas, on the other hand, any error occurred in smaller parts (triangle) is adjusted independently, and at the end of survey no error is left. Thus, the basic objective of this principle is to adjust the error locally within each small figure (triangle) independently and preventing the accumulation of errors.

The principle of working from whole to part means that when you survey a large area, you should first look at the entire area as a whole before breaking it down into smaller sections. Each section is typically shaped like a triangle. This is important because if you make a mistake while surveying a big area without dividing it, that mistake can turn into a big problem by the end of your work. On the contrary, if you survey smaller triangles, you can find and fix mistakes easily, which prevents errors from piling up. The goal is to keep surveying accurate by handling smaller pieces correctly.

Imagine you're constructing a large puzzle. If you try to put the whole puzzle together at once, it can get confusing and mistakes can happen. Instead, if you work on one small section at a time, like each puzzle piece, you can easily see where a piece fits, making it easier to fix any mistakes. This approach of focusing on smaller sections helps ensure the final puzzle fits together perfectly.

Horizontal control points in surveying are located by linear and/or angular measurements. If two control points are established by surveying measurements, a new point (third point) can be established with the help of these two known control points by taking two linear or two angular measurements, or by one linear and one angular measurement. In other words, indirectly the location of the new point is established using the geometry or trigonometry of the triangle formed by these three points.

This principle emphasizes the importance of using multiple measurements to determine the location of a new point. When you establish two known points (control points) through your surveying, you can find a third point based on these two. This can be achieved with two lengths, two angles, or a combination of one length and one angle. The method relies on the properties of triangles from geometry, where knowing certain measurements allows you to calculate unknown ones. By using this approach, surveyors can ensure their new point is accurately placed based on solid measurements.

Think of it like finding a location on a map. If you know where two landmarks are, like a library and a park, you can find a new location, like a friend's house, by measuring the distance from both the landmarks. This is similar to how surveyors triangulate the position of a point using measurements from two established points. By doing this, they confirm that the new point is correctly placed on the map, helping them avoid getting lost.

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