Theory of DGPS.
Now DGPS is broadly used in modern surveying techniques!
Hi everyone! Hope you all are good.
Today we are here with a new video that may help you to develop your surveying skills.
Every instrument has its own theory on the basis of that it gives us the output. Similarly DGPS also follow a theory! Today we will describe the THEORY OF DGPS i.e. How DGPS gives us accurate position data of a particular point and why DGPS is better than normal GPS.
Before going to discuss about the DGPS we must know about GPS because we are talking about D-GPS i.e. Differential Global Positioning System.
GPS a satellite based navigation system owned by US government and operated by the US space force which gives position data of a point.
Accuracy of GPS is 500 - 30 centimeter.
In GPS, total satellite is 33, among those 24 are functional and 31 are in 6 Orbit.
Like GPS, some countries have their own positioning system. Like-
1) GLONASS owned by Russian Government.
2) GALILEO owned by Europe government.
3) Compass (also known as Beido) owned by Chinese Government.
4) IRNSS owned by Indian government.
DGPS are working on a very important factor which is called GNSS i.e. Global Navigational Satellite System. That provides Geo location and time information to DGPS receiver.
GNSS is formed by GPS + any one of above four positioning system for better accuracy.
So by using GPS we can get position of any point on earth. So the question is Why DGPS? What is the Principle of DGPS?
And I will give the answer of this “WHY”
WATCH THE FULL VIDEO TO KNOW THE DIFFERENCE BETWEEN GPS AND DGPS AND WHY DO WE NEED DGPS.
In DGPS positional corrections to GPS data applied by way of BASE and ROVER system.
DGPS uses a known position to adjust real-time the GPS signal to get more accurate data.
In DGPS we use two identical GPS and both have the same identical components.
Like tripod stand, antenna, receiver, Controller etc.
Among them one is used as BASE and another is called ROVER.
Now I will discuss about the type of DGPS survey.
There are two types of DGPS survey that is static and kinematics.
Kinematics survey is further subdivided by two types one is called PPK post process kinematics and another is called RTK real time kinematics.
Static DGPS survey.
In static survey we use the DGPS for finding coordinate of an unknown point or establishing the control point for road or topographical survey. Usually we take data for 72 hours to get accurate position of an unknown point. We can take data for short period also but observations of 72 hours gives us most accurate result.
Now I am going to discuss about kinematic survey.
As I told before kinematics survey have two parts that is post process kinematics and real time kinematics.
In kinematics survey the concept of Base and Rover is applied. In post process survey, there is only satellite connection between both the identical DGPS and we get the data after processing in software.
But in real time kinematics survey, both the identical DGPS are connected by satellite and internet connection or by radio frequency. By using RTK we get data in real time during field survey, there is no need to process the raw data further like in PPK survey.
In normal GPS we take data of an unknown point with an accuracy of 5 to 10m.
But the DGPS Rover get corrected by the DGPS base we get data of a point with greater accuracy this is why DGPS is better than GPS.
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20 фев 2021
