Differential GPS & Real-Time DGPS, & Sources of Base Station Data, and DGPS Services (Especially for GATE-Geospatial 2022)

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What is Differential GPS?

  • Differential GPS is a method of increasing the accuracy of positions derived from GPS receivers. With DGPS receivers, position accuracy is improved from 30 m to better than 10 m.
  • Differential GPS (DGPS) was developed to meet the requirements of positioning and distance measuring applications that required the best accuracies. In this section, you will read about Differential GPS. The principle of DGPS is that any two receivers, relatively close together will experience similar atmospheric errors.
Differential GPS Enhancement Service, Screen Size: 4.3 Inch, …

Workings of Differential GPS

  • It is necessary requirement for DGPS that a GPS receiver be set up on a precisely known location. GPS receiver is the base or reference station the base station receiver calculates its position based on satellite signals. Thereafter this location is compared to the known location.
  • The difference is applied to GPS data recorded by the second GPS receiver, which is known as the roving receiver. The corrected information can be applied to data from the roving receiver in real time in the field using radio signals.
  • DGPS involves the use of a control or reference receiver at a known location to measure the systematic GPS errors.
  • Real-time DGPS occurs when on receiving data, the base station calculates and broadcasts corrections for each satellite. Further, the corrections are received by the roving receiver via a radio signal, if the source is land based or via a satellite signal, if it is satellite based.
  • This correction is then applied to the position it is calculating. Real-time differential corrections usage allows navigation within 1 to 2 m of any location depending on the service and GPS receiver.
  • The differential correction of GPS data by post processing uses a base GPS receiver that logs positions at a known location and a rover GPS receiver that collects positions in the field. The files from the base and rover are transferred to the office processing software, which computes corrected positions for the rover՚s file. This resulting corrected file can be viewed in or exported to a Geographic Information System (GIS) .
  • There are many permanent GPS base stations currently operating throughout the world that provide data necessary for differentially correcting GPS data. This data can be downloaded from the internet or via a Bulletin Board System (BBS) , depending on the technology preferred by the base station owner.

Sources of Base Station Data

Sources of base station data for post processing fall into four categories namely:

  • Public sources
  • Commercial sources
  • Web-based services
  • Base station ownership

DGPS Services

The various DGPS services available are categorized according to broadcast range of the correction signals:

  • Local DGPS are, basically, the Local Area Augmentation System (LAAS) but sometimes also called as the Ground Based Augmentation Systems (GBAS) .
  • Regional DGPS
  • Wide Area DGPS (WADGPS) or Satellite Based Augmentation Systems (SBAS) employ satellites to transmit DGPS correction data.

Developed by: