When discussion the accuracy of a GPS system it is important to distinguish b/w absolute positioning v’s relative positioning.
Absolute positioning is your exact location at any given time on Earth (indicated by a Latitude and Longitude).
Relative positioning is the actual distance travelled as indicated by the GPS from a start point to a known end point.
The image to the left shows that on any given day your absolute positioning will be +/- 2-5m of the true location BUT if you travel a known distance (regardless of your starting point), the accuracy of a system like the AxSys system will be around 99% of true distance.
It is for this reason that being able to accurately display player to player positioning is difficult due to the absolute positioning error, but the distances covered by the athlete (relative positioning) are very accurate and reliable.
There are methods to improve on the absolute accuracy of a GPS system, but this typically involves additional technologies and increased cost.
If you are interested in a reasonable estimation of the positioning of your player – then the absolute positioning error of systems like the AxSys system is likely to be acceptable.
As with all things GPS, the clearer the area that the data is being collected (eg open field), the better chance of capturing accurate performance data.
We are regularly asked “How accurate is the GPS product we have” – Before we can answer this question appropriately we need to explain the difference between Absolute and Relative Positioning and the associated accuracies when applied to a sporting environment.
In the next article in this series we will explain why GPS is not cm level accurate and highlight how you can use the technology to ensure the most accurate signal possible.