What is the difference between absolute and differential GPS?

2 Differential GPS

Differential GPS (DGPS) is a method of GPS positioning that improves the accuracy of absolute GPS by using a second GPS receiver. The second receiver is called a reference station and it is placed at a known location. The reference station monitors the signals from the satellites and compares them with its actual coordinates. It then calculates the errors and sends them as corrections to the other receiver, which is called a rover. The rover applies the corrections to its own measurements and obtains a more accurate position. Depending on the type and frequency of corrections, differential GPS can achieve an accuracy of 1-5 meters or less.

3 Types of DGPS

Differential Global Positioning System (DGPS) comes in various forms depending on the source and format of the corrections. Real-Time Kinematic (RTK) uses a radio link to transmit corrections from the reference station to the rover with a high frequency, usually 1 Hz or more, and can achieve an accuracy of 1-3 centimeters or less. However, it requires a clear line of sight and a short distance, typically less than 10 kilometers, between the receivers. Post-Processing Kinematic (PPK) utilizes a data logger to store raw measurements from both the reference station and the rover, with corrections applied later using a software on a computer. It can reach similar accuracy as RTK but requires more time and effort for processing after fieldwork. Wide Area Augmentation System (WAAS) relies on a network of ground stations and geostationary satellites to provide corrections over a large area, such as a continent. WAAS can improve absolute GPS accuracy to 3-5 meters or less without additional equipment or cost for the user; however, it depends on the availability and coverage of WAAS satellites and stations.

4 Applications of DGPS

DGPS has many applications in GIS, especially for projects that require high accuracy and precision. For example, it can be used for surveying and mapping to collect and update spatial data for various purposes, such as land use, infrastructure, natural resources, and environmental management. Additionally, DGPS can be used for navigation and tracking to guide and monitor the movement of vehicles, vessels, aircraft, and people in various domains like transportation, logistics, security, and recreation. Finally, it can be used for research and education purposes to conduct and support scientific studies and experiments that involve spatial data and analysis in disciplines like geology, ecology, archaeology, and geography.

5 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?