Local Area DGPS (LADGPS) is a form of Differential GPS (DGPS) that provides GPS signal corrections within a relatively limited coverage area, usually around the vicinity of a single reference station. Here are some key points about LADGPS:
Reference Station: LADGPS operates with a single, fixed reference station that knows its exact position. This station receives GPS signals and determines the difference between its known position and the position indicated by the GPS signals.
Correction Signals: Based on the discrepancy determined, the reference station calculates correction data and broadcasts it to DGPS-equipped receivers within its coverage area.
Coverage Area: LADGPS typically has a limited coverage area, often ranging from 10 to several hundred kilometers, depending on the transmission power of the reference station and the geography of the area.
Accuracy: With the corrections applied from LADGPS, receivers can achieve positioning accuracy within 1 to 3 meters, and sometimes even better.
Applications:
- Maritime Navigation: Ports and harbors often use LADGPS to aid ships in navigating tight channels and berthing.
- Surveying: Surveyors can use LADGPS to obtain accurate position data without setting up a temporary base station.
- Agriculture: Precision farming techniques often utilize LADGPS for tasks like planting, harvesting, and soil sampling.
Limitations:
- Limited Range: Since LADGPS typically operates with a single reference station, its range can be limited, especially when compared to Wide Area DGPS (WADGPS) systems which cover much larger areas.
- Geographical Limitations: Mountains, tall buildings, and other large structures can limit or interfere with the broadcast of correction signals.
Alternative Solutions: In areas where LADGPS signals are not available or reliable, other DGPS methods such as WADGPS or satellite-based augmentation systems (SBAS) might be used.
In essence, LADGPS offers a solution for improving GPS accuracy in a localized area, making it suitable for applications that require high precision but don’t necessarily need widespread coverage.