Difference Between Plane Surveying and Geodetic Surveying
Difference Between Plane Surveying and Geodetic Surveying
Introduction
Surveying is the science of measuring the earth’s surface. The concept of “surveying” has been around for a long time, and its use dates back to Biblical times.
Surveys are carried out using instruments such as topographic surveys, cadastral surveys, and satellite mapping.
Plane surveying is a type of surveying in which the earth’s surface is regarded to be a plane surface. Earth curvature is not counted in distances for small projects covering less than 250 sq.km.
If the area to be surveyed exceeds 1000 km2, the angles measured on the earth’s surface cannot be in a plane but must be on a curved surface; hence, geodetic surveying must be used to attain precision for vast regions.
Geodetic surveying is a type of surveying in which the curvature of the earth is taken into account when collecting measurements on the earth’s surface.
When the survey covers a broad region (more than 250 square kilometers) and the degree of precision is high. Geodetic surveys are used to give control points for smaller surveys to link to.
Difference Between Plane Surveying and Geodetic Surveying
The following differences exist between plane surveying and geodetic surveying.
Angle of the Instrument
In plane surveying, the angle of the instrument used is more than 90º (inclusive) but less than 180º (exclusive).
The above angle is called a quadrantal angle. Geodetic surveying, on the other hand, involves measuring angles in an instrument that ranges 180º.
Survey Areas
The survey areas for plane surveying are large. Surveyors use a small number of angles to cover the entire area. In geodetic surveying, the regions to be surveyed are small but must be accurately measured.
Control Points
Control points are established in plane surveys so that more accurate measurements can be made later on; whereas, geodetic surveying does not require this.
Data Acquisition
In plane surveying, data is always collected from one point to another in a straight line without having to backtrack; this is not the case with geodetic surveying. Because straight lines do not exist on earth, data should be collected using a curved line.
For this reason, data must be acquired in a series of short segments. In geodetic surveying, the surveyor must use a series of different measurements to calculate distances between survey points so that he can construct a curve.
Analysis of Surveys
Planning for a plane survey requires surveyors to draw a map with the already surveyed shapes and the desired shape in mind. However, geodetic surveying has no such planning requirements; it is mainly a measurement process.
Cost and Time
Plane surveys are relatively easy to carry out. The process requires a small number of instrument operators who together carry out a survey that covers only a small area.
In geodetic surveying, control points are established for entire regions, and the cost is very high due to the use of specialized measurements throughout the entire survey area.
Geodetic surveying requires high levels of input, and it is an expensive technique. Plane surveys are easier to carry out and have a lower price.
Speed
Plane surveying is faster in carrying out the measurements but does not provide high levels of accuracy; hence, it is used for relatively small areas. Geodetic surveying takes a long time to cover broad areas with accurate measurements; it is useful for industry and commerce because a very small error may lead to huge loss or waste.
Areas Covered
Plane surveying covers large areas; hence the need for large numbers of control points, whereas geodetic surveying covers small regions requiring fewer control points.
Surveying Results
Plane surveying can only give general information about the surface of the earth, whereas geodetic surveying gives highly accurate information about the height and length of features on the earth’s surface.
Precision for Small Surveys
With plane surveying, precision is achieved for small surveys. Precise heights and lengths can be obtained for a small survey area covering less than 250 square kilometers in a single direction.
With geodetic surveying, precision is achieved for large surveys as each control point must be measured using an instrument with a level of precision that is 1/10th of the unit used.
Accuracy
Plane surveying can be accurate to within a few centimeters; whereas, geodetic surveying can be accurate to within millimeters.
The basis for the Surveys
Plane surveys are conducted using plane geometry and trigonometry, whereas geodetic surveys are based on spherical geometry.
Surveyor’s Pay
Plane surveying is a job for less-skilled surveyors. Skilled surveyors are required for geodetic surveying; hence, the pay is higher than plane surveying.
Certain areas of knowledge and tools used in these two different types of surveys are listed below:
- Plane Surveying- distance measuring instruments, theodolites, transits
- Geodetic Surveying- Total stations, GNSS receivers (GPS), angles and distances measuring instruments.
Spherical and Ellipsoid Earth Models
The earth in geodetic surveying is conceptualized as an oblate spheroid; this is not so in plane surveying, where the earth is conceptualized as a plane surface.
Geodetic Surveying
Geodetic surveys have an error margin of about 0.5cm. This is vastly different from plane surveying, which gives accuracies of a few centimeters.
Degree of Precision
Plane surveying gives general information about the earth’s surface, whereas geodetic surveying has high precision and accuracy of measurements in terms of the size and shape of features on the earth’s surface.
A ruler that is accurate to within a few centimeters, can measure a distance of 1 meter accurately. However, if the ruler is accurate to within 1/10th of the unit used, then it can measure distances ranging from 0.001 mm to 0.05m with an accuracy of better than 99.9999%.
Conclusion
Plane surveying is easier to carry out and does not require expensive instrumentation. It is good for small areas, but it cannot provide high levels of accuracy.
Geodetic surveying takes much time to cover vast areas with accurate measurements, and the precision lost in a border line area can lead to huge losses.
FAQs
What is the difference between geodetic surveying and plane surveying?
Plane surveying uses the idea of a flat surface of a sphere to describe the earth’s surface. It carries out surveys based on linear geometry, distance and angles measurements.
Geodetic surveying uses spherical geometry and trigonometry to give high precision in terms of the size and shape of features on the earth’s surface.
What is geodetic surveying?
Geodetic surveying is a survey technique that measures the curvature of the earth in order to determine the height and length of objects on the earth’s surface. It involves measuring angles, distances and heights of points on Earth using control points.
What are the main benefits of geodetic surveying?
Geodetic surveying has high precision and accuracy in terms of the size and shape of features on the earth’s surface. It is used in industries and commerce to establish the size and shape of features on the earth’s surface.
What is plane surveying?
Plane surveying uses plane geometry and trigonometry to measure distances and angles. Plane surveying is suitable for relatively small areas as it has a high level of accuracy. It uses fewer control points than geodetic surveying.
What are the main benefits of plane surveying?
Plane surveying gives general information about the earth’s surface, whereas geodetic surveying has high precision and accuracy in measuring the size and shape of features on the earth’s surface.
Why is plane surveying used?
Plane surveying is used because it is quick, cheap and easy to use. It does not require expensive instrumentation.
Is geodetic surveying accurate?
Geodetic surveying is accurate, but it cannot give the same accuracy as plane surveying.
How much time does it take to survey an area with plane surveying?
The amount of time required to survey an area using plane surveying depends on the accuracy required. Small surveys can be done in a few days or weeks, whereas large surveys can take years.
Can plane surveying give the same level of accuracy as geodetic surveying?
Plane surveying does not have the same level of accuracy as geodetic surveying. It depends on the size and shape of the area being surveyed.
What is the difference between a sextant and an angle measure?
A sextant is used for measuring angles in geodetic surveys; whereas, an angle measure gives precise measurements of the length and height of objects on the earth’s surface.
How many control points are required for geodetic surveying?
The number of control points used in geodetic surveys is 3 to 5 times more than the number required for plane surveys. This is because a geodetically surveyed area can have a huge distortion.
Why are more control points needed for surveying?
Control points play an important role in a survey since they determine the accuracy of the measurements. More control points also give more information about survey areas which can be useful.
How does a surveyor measure the length of an object?
A surveyor measures the length of an object using a vertical and horizontal angle. The distance is a product of these two measurements, which are equal if the angle is 0 degrees.
What are the different types of surveying tools used?
A surveyor uses two types of surveying equipment to map an area; namely, sighting instruments and measuring instruments. Sighting instruments are used to measure angles, and measuring instruments are used to measure distances. A surveyor also uses surveying software for data collection.
Why geodetic engineering is important?
Geodetic engineering is important because it gives the size and shape of features on the earth’s surface. Further, it helps in calculating the extent of underground areas too.
What are some other uses of geodetic surveying?
Other uses of geodetic surveying are as follows:
- It is used in agriculture to map out different types of crops planted on land and determine the amount of land that can be tilled or irrigated with different kinds of crops.
- It is used in construction to give the amount of land that can be used for different purposes like housing or industry.
- It is used in transportation to calculate the number of parking lots, traffic lanes and highways that can be constructed along a road according to the dimensions of cross-sections and traffic density.
- It is used in astronomy to measure distances between stars and galaxies within a galaxy cluster to determine their size, shape and density.
- It is used in surveying, engineering and architecture to map out underground areas and determine the size and shape of tunnels, buildings etc.
- It is used in oceanography to measure the depth of oceans and calculate the depth of land masses as well.
- It is used in cartography to measure distances between locations on Earth’s surface using angles with an accuracy of 0.01 degree for a single control point.
What are some other uses of Plane surveying?
Besides the standard uses of plane surveying, there are some other uses as follows:
- It is used in meteorology to measure the height of storm clouds and predict their paths and movement.
- It is used in hydrology to calculate the flow of water through various bodies of water like rivers, lakes and streams.
- It is used in navigation to measure distances between objects like ships at sea or aircraft during take-off and landing.
- It is used in archeology to measure the distance between various monuments and determine their size and shape.
- It is used in mining to measure the distances between tunnel entrances and make sure that rocks are loaded safely into trucks or carts.
What are the types of geodetic survey?
For finding the exact locations of points on the earth’s surface, four conventional surveying techniques are commonly used: (1) astronomic positioning, (2) triangulation, (3) trilateration, and (4) traverse.
What are geodetic techniques?
Geodetic Methods. Global Positioning System (GPS). Satellite-Based Doppler Orbitography and Radio positioning Radar using Interferometric Synthetic Aperture. Laser ranging from space.
What is geodetic science?
Geodetic science deals with the measurement of the earth’s size and shape. It gives information about the size and shape of features on the earth’s surface.
What are some applications for geodesy?
Geodesy applications include surveying, navigation, mapping and measuring distance. Geodesy is used for real-time observations such as snow depth. It is also used to measure the length of underground areas and is useful in mines, tunnels and road surveys.
How is geodetic survey handled in Antarctica?
Because of the rugged nature of surface, Antarctic geodetic surveying requires special surveying techniques. The most useful surveying technique that has been used by Antarctic surveyors is the UTM (Universal Transverse Mercator) projection system.
The UTM (Universal Transverse Mercator) projection system, adopted for most of the countries in the world, is used for geodetic surveys.
The major difference between UTM and Gauss/Siebel projection for geodetic surveys is that the former uses projectors to project lines of longitude and latitude and synchronizes them with other lines that are projected using paleographic methods.