How are the measurement results evaluated?

The evaluation differs fundamentally from all “usual” methods, which have hitherto been used to determine the CdA value. In the method used by us, first, the speed is simulated with the recorded data. This is done using the Newtonian equation of motion, which, in contrast to many other methods, is solved numerically with a differential equation solver that is used as a standard in science. Thus, the model error is substantially smaller than if, for example, the acceleration is neglected, as is often the case. The error of the numerical solution is less than 0.0001 m² and is therefore negligibly small. The simulated speeds are compared with the measured speeds in a so-called “parameter fit”. The parameters, such as, the CdA value and the average wind speed, are adjusted as long as the deviation between simulation and measurement is as small as possible. It is then also possible to determine the statistical measurement error, which is generally about 0.005 m². Wind direction changes can thus be taken into account precisely, too. The still dominant measurement error is a non-constant seating position.