GPS Basics: Overview of GPS

 

There are many myths around the use of GPS in sport – This series aims to highlight the strengths and weaknesses of GPS technology and associated sensors (Accelerometers/Gyroscopes) for use in a sport environment.
 

Firstly, there is no doubt that Sport GPS units have changed the team sport landscape for ever. Gone are the days of guestimating how much work has been completed by each individual player. With the advent of accurate, small GPS units, coaching staff now have access to all key metrics needed to make informed decisions on training loads and intensities.
 

 

 

 

 

GPS BASICS:

  1. GPS is a free technology (No fees to be paid to access the signal).

  2. GPS does not need to be calibrated, it self-calibrates.

  3. GPS only works outdoors (requires a direct line of sight from the satellite to the GPS receiver in your device/phone).

  4. GPS has a position error (where you are located on the Earth) of between 2-10m depending on the environment and quality of GPS module.

  5. GPS doesn’t like built up environments (city centres, forests) – the accuracy will decrease in these environments.

  6. GPS uses two methods to calculate distance/speed of a user

    1. Latitude/Longitude/time, or

    2. Doppler (rate of change of the GPS signal reaching a GPS module).

  7. There are 20+ GPS satellites in the sky in most regions of the world.

  8. There are multiple GPS companies with GPS satellites in the sky – Most modern GPS units will have GPS modules that can see 2 or more of these systems (ensuring very good satellite coverage anywhere on Earth).

  9. Only 4 satellites are required to generate an accurate and reliable position.

  10. GPS devices have different update rates – Typically your phone or GPS watch will only sample at 1Hz (once per second) – this is not suitable for rapid change of direction activities as would happen in a team sport environment.

  11. The team sport specific GPS devices have sampling rates 10Hz or more.

    1. AxSys GPS has a sampling rate of 18hz – leading to a very high accuracy of all GPS metrics.

  12. GPS can be used to capture the following performance metrics from an athlete:

    1. Position

    2. Distance

    3. Speed

    4. Acceleration

    5. Deceleration
       

Summary Video: How Does GPS Work? by sciBRIGHT - https://www.youtube.com/watch?v=FU_pY2sTwTA

 

SUMMARY

GPS technology is a free platform that can allow for accurate measurement of sport performance.

There are some limitations to the technology, that if you understand and avoid will maximise your use of GPS technology in your training.

In the next article in this series we will explain the difference in accuracy using GPS (Absolute versus Relative positioning accuracy).

 

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