Land Surveing – Surveying types
What is surveying?
Surveying is the process of determine the location of a point on the earth’s surface, relative to other points with the help of measured horizontal distance, vertical distance, direction and angles among those points. Surveying is done to prepare a map to locate the needed point using the known or calculated survey data.
Type 1: Plane surveying
Plane surveying is the process of surveying by assuming that the earth is flat. Which mean the curvature or spherical shape of the earth is not considered in plane surveying calculations. Hence, a line obtained by connecting any two points of earth’s surface is considered as straight line and angles obtained within those lines are considered as plane angles. In construction field plane surveying is the first step on most of the projects. Surveying experts noted that plane surveying is more accurate when the area is small (But here small area can refer up to 250km…!). Basic plane geometry and trigonometry are necessary to carry out plane surveying calculations. In plane surveying linear measurement and angular measurement are the two important components.
Type 2: Geodetic surveying
Geodetic surveying is a process of surveying by considering the curvature or spherical shape of the earth. The exact positions of points obtained on plane surveying are given by geodetic. Other than that geodetic survey is done for large areas and lengthy lines. Hence, the lines connecting any two points are considered as arch. Special instruments and knowledge of spherical trigonometry is essential for the accuracy of geodetic surveying. As the earth is irregular in shape (experts noted that earth is not spheroid as it doesn’t fulfil the spheroid rules) accurate positions are needed for wide range of purposes where accurate mapping is necessary. At this stage geodetic survey helps to fulfill the need. Triangulation and accurate traverse are the methods used in geodetic surveying.
Difference between plane surveying and geodetic surveying
|Plane Surveying||Geodetic Surveying|
|Earth surface is assumed as plain||Earth surface is considered as spherical|
|Line formed by any two points are considered as straight line – as the same angles are plain angles||Line formed by joining any two points are considered as arch –as the same angles are spherical angles|
|Suitable for small area surveying||Suitable for large area surveying|
|Survey accuracy is low||Survey accuracy is high|
|Economic and easy survey method||Special instrument needed and long survey method|