Surveying and mapping was one of the very first commercial adaptations of the GPS platform, as it provides a latitude and longitude position directly without the added need to measure angles and the distanced between points.
However, GPS hasn’t wholly replaced surveying field instruments including the Theodolite or the Electronic Distance Metre, due to the costs of the technology and the requirement for GPS to be able to visibly see the satellites and therefore restricting its use close to trees or taller buildings.
When surveying with GPS, rather than the outright positions being measured, the baseline or 3D distance between 2 points is computed instead. In most cases the answer isn’t instantaneous. The GPS data has to be simultaneously collected at both points, with the data being used later on to determine the structured baseline. This method is known as Static GPS.
Although some systems can compute the baseline right away, in real time to give an almost instant answer. This is known as Real Time Kinematic or (RTK GPS) for short.
GPS measurements of the baseline between the 2 points can be extremely accurate. This relative positioning of the points is much more accurate than instant absolute positioning using just one receiver.
With GPS surveying at least 2 receivers are needed. This is to produce accurate and absolute positions with one receiver being at a known point.
The carrier wave of the coded signal is used rather than the coded signal itself.
The range to the satellite is then determined by calculating the whole number of wavelengths between the actual receiver and the satellite.
The final result of the data being processed is a computation of the baseline that is between the 2 receivers. This combination of data cuts out many of the potential errors, giving an accurate baseline result.