TestResults / Conclusions
- The DL2 represents the state of the art with regard to GPS measurements as applied to vehicle testing. It utilises advanced post-processing techniques to achieve high performance and accuracy. The DL2s GPS system is also unique in that it has been specifically optimised for vehicular applications.
- Assuming a similar specification of GPS receiver noise performance, a 100Hz GPS system does not outperform a 20Hz system for vehicle testing applications; however a 20Hz GPS system does outperform a 5Hz system.
- Differential GPS corrections only improve positional errors; they have no direct or significant effect on speed or distance.
- From the tests comparing the VBOX3 with the 20Hz DL2, the performance of the systems are broadly equivalent; although the noise in the VBOXs speed output is significantly higher due to its higher sample frequency. No firm conclusion can be drawn against the optical system: Tests results on the day were poor; however this may have been due to the damp track.
- Positional accuracies are in the sub meter range for the DGPS DL2. For a standalone DL2 (without WAAS or EGNOS) the positional accuracies are in the 3m range (50% COP). These results are entirely consistent with other GPS system and are largely limited by the physics of the GPS system not the receiver.
- The speeds from the DL2 are exceptionally accurate both dynamically and statically – the actual level of accuracy of the system is difficult to conclude as no definitive reference is available, however the system certainly achieved better than 0.1kph even with high speed dynamics.
- Distance accuracies of the DL2 for a typical acceleration/braking test are in the range of a few centimetres. Again it is difficult to state a precise level of accuracy, as it is limited by the practical experimental errors.