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DGPS Survey

 

DGPS

What is DGPS? DGPS (Differential Global Positioning System) survey is a surveying method that uses a combination of GPS and a reference station to improve the accuracy of GPS data. In a DGPS survey, a reference station is set up at a known location and the GPS receiver at the survey location takes measurements from both the GPS satellites and the reference station. The reference station then uses these measurements to calculate and transmit correction factors to the GPS receiver, which are used to improve the accuracy of the GPS data.

Why does it required ? DGPS survey is required in a variety of applications such as mapping, navigation, and land surveying. It is particularly useful in cases where high accuracy is required, such as in construction and engineering projects, where even small errors in position can result in significant cost or safety issues. It is also used in marine navigation, where safety and navigation accuracy is critical. In addition, DGPS survey is also used in precision agriculture, where accurate location information is needed for planting, harvesting, and other tasks.

Overall, DGPS survey is a powerful tool that can significantly improve the accuracy of GPS data, which is crucial in a variety of applications. This is why it is required in many types of surveying, mapping, and navigation projects where precision is important.

DGPS SURVEY METHODOLOGY

DGPS survey is the survey carried out to fix the horizontal and vertical control points in an area. DGPS uses position corrections to attain greater accuracy. It does this using a reference station. The reference station (or base station) may be a ground-based facility or a geosynchronous satellite; in either case it is a station whose position is a known point. This process has been adopted to check the coordinates of points established. This process has been mainly adopted to speed up the work as the ground condition became difficult due to the obstruction caused by crops such as sugarcane and high bushes.

 

Principles of DGPS Survey

Differential GPS (DGPS) gets around the accuracy problem by relying on a number of fixed points on the earth whose GPS coordinates are well-known. Base stations or reference stations are located at these fixed points. The DGPS system works as follows:

  • Base stations constantly measure the accuracy of the GPS signal received from each of the satellites that it has a Line-of-Sight (LoS) or direct visibility to.
  • The base station calculates how much of a correction (compared to the known accurate position) is required per satellite and broadcasts this information to DGPS units in its vicinity.
  • Using the original signal received from the satellite and the correction information received from the nearest fixed point (or points) the DGPS unit can then establish a more accurate estimate of its current position.

The basic assumption is that GPS receivers that are close to each other suffer from similar atmospheric effects, and so in all likelihood the base station and the closest DGPS unit will experience the same amount of error. Clearly, the accuracy of DGPS will depend on the distance from the closest base station. A DGPS unit, thus, needs to have the additional capability of receiving the signal from base stations) and carrying out the post-processing.








Advantages Disadvantages
Improved accuracy compared to traditional GPS survey methods More expensive equipment and setup required
Can be used in areas with limited satellite visibility, such as urban or forested areas Additional infrastructure, such as reference stations, required to be in place to receive and transmit correction signals
Real-time correction signals can improve survey efficiency and reduce survey time Errors can still occur if correction signals are not received or are delayed, which can result in inaccuracies in the survey data
Can be used to survey areas with large bodies of water, such as oceans or rivers Limited availability of correction signals in remote or inaccessible areas, which can limit the usefulness of DGPS in these areas
Can provide sub-meter level accuracy for surveying and mapping applications Requires a clear line of sight between the DGPS receiver and the correction signal source, which can be blocked by buildings, trees, or other physical obstructions, which can limit the signal strength.
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