In today’s Tutorial we would like to show you the reason for our strong recommendation to use a speedsensor when you are conducting our aeroTEST. Every GPS device provide different values in regards to the quality of the data recorded. Since even models within the product line of one manufacturer have different quality levels we do not want to go into details of manufacturers. More important for us is to show you the different levels of quality you can reach and therefore how strong the results of your aeroTEST are by using a speedsensor or not. Our aeroTEST is based on a 1km long test stretch. By using a speedsensor you will be providing a konstant rate of data to your GPS device, which could be influenced by external factors (e.g. Trees, Buildings, …). Over a long period of time this can be mitigated, such as single sided powermeters. However over the short stretch used by us for the evaluation of our test ± 2km/h within a series of measurement intervals makes a big difference.

To illustrate this, we will use the following two pictures.

speedsensor

Picture 1 shows a test without speedsensor. The CdA value of this test is not important, since we took a random test. You can see in the pictures that the value measure was ±0.065 m2 from the mean value. This measurement error is too big and therefore the result provided is too weak to give a reliable statement.

speedsensor

Picture 2 show a test with speedsensor. Since this is from a different test, you cannot compare the CdA to the one from Picture 1, however, as you can see in the picture is the measurement error ± 0.004 m2.

Sure, we used a very extreme example in picture 1. Our fixed value for having a reliable result is below ± 0.010 m2. Therefore you cannot use the test from picture 1 for a reliable analysis.

Our recommendation is the classic speedsensor which is installted on the spokes (ANT+ or Bluetooth capable, so it will deliver data to your GPS device). An alternative is the Hub based speedsensor shown on the right of the picture below, however the data provided by these is not as strong as by the classical ones.

speedsensor

So go out and test, stay aero and become afasteryou!