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GPS Surveying

What Is GPS?

GPS is short for Global Positioning Systems.

GPS is an accurate navigation system that uses signals from various satellites to correctly determine a location on the Globe’s surface, regardless of the weather conditions.

This system is solely dependent on GPS satellites that are located in our orbit, high above the earth which then transmits signals containing the actual time and location of the satellite. Any ground-based receiver that receives the signals from 4 or more GPS satellites can use navigation calculations to determine its location on the Earth’s surface. Continued signalling can then update the speed and direction information for the moving receivers.

GPS was only originally developed for military usage, but since the early 90’s it has been released for civilian use and is now used regularly in various applications such as mobile phones, SAT Navs and of course mapping and surveying.

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Call Wayne Evans Surveying Ltd Today

If you would like to find out more regarding GPS Surveying or the benefits of a GPS Survey, call the professionals at Wayne Evans Surveying Ltd.

You can reach us by calling on 07736 740802.

Surveying with GPS

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.

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