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FASTLOC™ Performance * *Note - For latest performance statistics the download the Technical Report TR01 - Download TR01.pdf Tests of the Fastloc™ Version 2.2 firmware have provided location estimates with a typical accuracy of <50m, the figure below illustrates the spread of location estimates around a fixed point from 10,000 position measurements taken over a period of over 2 days. The location of the receiver was suburban with a partially masked view of the sky. Location estimate outliers are typically the result of solutions from <7 satellites.
The results highlight a reasonably accurate location solution, comparable with standard GPS receivers when Selective Availability was switched on. The next figures illustrate the cumulative density plot of location errors. It can be seen that the more satellites detected the better the location solution e.g. for >10 satellites 100% of the solutions will be within 50m and 50% will be within 13m accuracy.
Fastloc™ positioning is most effective when more than 5 satellites can be tracked by the receiver. However a location estimate can be made with just 4 satellite detections, but as has been highlighted in the previous plots, errors can be high.
Table 1. Location estimation error as a function of satellites detected Table 1 presents the horizontal location estimation error performance in relation to the number of satellites detected†. CEP is the circular error probability, this is the circle radius within which 50% of locations will lie. The RMS error becomes distorted by large outliers as the number of satellites declines, normally the RMS can be considered to be the standard deviation of the error, however in reality >80% of locations will be better than the RMS for locations from 5-7 satellites. Because of this distortion the actual 95% confidence limits are also presented. Notes: † Fastloc™ enhanced tags running version 2.1 firmware will have degraded performance from that specified * Processing of locations from 4 satellites uses fixed height processing to reduce error, there is no 3D location.
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