Introduction to the DL2’s GPS technologies
The most revolutionary feature of the DL2 is that the logger unit records the raw GPS transmissions, these are then converted into “physical data” (acceleration, speed, distance and position) once the data has been transferred to computer - this approach is generally termed “post processing”. Although the post processing approach is new to the world of automotive testing, it has been used for many years when using GPS for surveying and it has several very important advantages:
- The processor in an average PC is hundreds of times more powerful than the microcontroller embedded on a GPS card, so more advanced processing techniques can be used.
- When post processing the GPS data, it can be processed forwards and backwards. This has a number of advantages; normally, after passing an obstruction for say one second (such as a bridge) a GPS system can take around ten seconds before it reaches maximum accuracy. By processing the data backwards, this period of inaccuracy is eliminated – so instead of having no data for one second followed by ten seconds of poor data, a post-processed solution will provide one second of no data then optimal data immediately afterwards.
- All the GPS code has been developed in-house by Race Technology Ltd, with the assistance of some of the leading GPS consultants in the field. All the intellectual property and program source code is the sole property of Race Technology Ltd, and as such we have complete control over all aspects of the processing – there are no unknown mystery black boxes to “tweak”. The system has been designed from the outset for automotive applications and is heavily optimised for this task. The DL2 is the only product that can claim this – in contrast, all other automotive test systems on the market rely on standard “general purpose” GPS boards. The Race Technology GPS system is optimised for the task in a number of key areas, in particular the GPS processing system has been programmed with knowledge of:
- The limits of the vehicle’s dynamics, including physical limits of longitudinal acceleration, lateral acceleration, velocity and rates of roll/pitch/yaw.
- The physical limits of possible vehicle manoeuvres, for example minimum turning radius, maximum gradient that vehicle could climb, etc.
- Using this knowledge about the physics of the vehicle, the GPS software engine can be optimised in many areas to produce highly accurate data without having any negative impact on the data that would occur with traditional “filtering”.