Plane Surveying vs Geodetic Surveying
Surveying can simply be defined as the process or technology of making measurement in a scientific manner on, above, or below the earth’s surface in order to determine points to produce a plan or map. When the area of surveying is small, and the scale to which its result plotted is large, then it is known as plan, and the vice versa of this is Map. Surveying is widely used in almost all civil engineering projects such as construction of building, bridges, reservoirs, dams, railways, roads, irrigation projects etc. Surveying can be classified based on different factors such as field of survey (like land survey, marine survey, photogrammetric, etc), object of surveys (like Engineering purpose, military purpose, etc), method of survey (like Triangulation, Trilateration, etc), and instruments used (Like chain surveying, theodolite surveying, levelling, etc). However the prime classification of surveying is plane surveying and geodetic surveying.
Plane Surveying
Plane surveying is a branch of surveying in which the surface of the earth is considered as plane surface. This is the most commonly practicing form of surveying. This is used when the extent of the area to be surveyed is small (area less than 260 square km) as this method neglects the curvature of earth. In order to make calculations, normally triangles are formed on the ground and these triangles are also assumed as plane triangles and the rules of plane triangles are used to do the computations. The area to be surveyed, and the error associated to the survey results are positively correlated that is more the area more the error. So, this method is not suitable for more accurate or precise large area surveying. Normally Plane surveying is useful for engineering projects. Normally, Survey for location and construction of railroads, highway, cannel, and landing fields are categorized under this method.
Geodetic Surveying
Geodetic surveying is another branch of surveying in which the curvature of the earth is considered when taking measurements on earth’s surface. That is the actual spherical shape of earth is taken into account. This is also known as trigonometrical surveying. The triangles formed are spherical triangles and calculations are made using spherical trigonometry. In this method, measurements are taken using high precision instruments. This method is used to determine or establish control points for other surveys, and to long lines and areas. The position of each geodetic station is expressed using longitude and latitude and Global Positioning System (GPS) is normally used for this purpose.
What is the difference between Plane Surveying and Geodetic Surveying?
Though, both plane surveying and geodetic surveying are the methods of making measurement on earth, they are having some distinguishing features.
1. Mainly, plane surveying ignores the curvature of the earth, while geodetic surveying consider it.
2. Plane surveying is suitable for small areas, whereas Geodetic surveying suits for surveying of large area.
3. Geodetic surveying is more accurate than plane surveying.
4. Triangles formed in plane surveying are plane triangles, but triangles formed in geodetic surveying are spherical triangles.
5. Geodetic stations are in huge distance compared to stations formed in plane surveying.
6. More over plane surveying uses normal instruments like chain, measuring tape, theodolite, etc to locate points on earth, while geodetic surveying uses more precise instruments and modern technology like GPS.
A fine illustration to each and every one to know the merits of land surveying.
S.Shajahan
Salem
Tamilnadu
India.
Why can’t curvature be detected over water?