Not all GPS data loggers are created equally

As with any high technology equipment GPS technology is constantly evolving. New GPS receivers are constantly being introduced, but are they all the same? Do the latest technologies and possibilities of higher accuracy benefit our application of automotive data logging?


Here at Race Technology HQ, our engineers evaluate new technologies to make sure that our products and knowledge remain at the cutting edge. This latest test was to make sure that the performance of the GPS receiver we are using in the DL1 is still the best for our application. We are undoubtedly pleased with the results and are confident that the DL1 has a GPS system to compete with the best of them.

The testing took part at Cadwell Park using fully prepared open-top race car, with the antenna mounted towards the rear of the car. All of the data was logged within the same run at the same time on one car with three data loggers. This means that the test was fair as they all experienced the same conditions and the same view of the sky/satellites, so the results are directly comparable. The environment at Cadwell Park is quite varied with some clear open sections and a few tree-lined areas. The varied conditions were chosen intentionally to be challenging and to give a realistic representation of typical GPS conditions in a typical racing environment.    

Three different receivers were tested: a high end receiver from an expensive automotive data logging system, a survey grade receiver, and the receiver used in the DL1 data logger. The data recorded was the raw GPS position directly from the receivers so no processing was allowed to increase the accuracy. The raw GPS positional accuracy is the key factor in getting reliable speed, position and distance data. Post-processing can make further improvements, but it can only make real improvements to data that is accurate in the first place. The raw GPS data from the different receivers was then simply plotted using a standard spreadsheet program to produce a familiar track map view.

When looking at the results the key points to look for are close grouping and consistency in lines and shapes between the different laps.

 

The data above is from a receiver used by a well-known competitor. The data loggers that use this receiver cost 10 times as much as the DL1. This receiver performed quite well in the open sections of the track, but was let down by some inconsistent results in the tree-lined, more challenging environment.

 

The data above is from a "Survey" grade receiver, which combines the data from both the United States Global Positioning System satellites and its Russian counterpart GLONASS (Global Navigation Satellite System). This receiver is very expensive and represents the latest in satellite navigation technology. The positional accuracy for this receiver is very good, excellent in the open sections, but again we see some inconsistency in the more challenging areas. The shapes are all the same, more or less so these would be considered good results.

The results shown above are from the receiver we use in the DL1. The consistency in the open areas is excellent, comparable with the expensive survey grade receiver. It does however show a bit more consistency and grouping in the tricky tree-lined sections of the track. We are very proud of our DL1 and this is a great result to show that it not only offers exceptional value for money, but can also outperform far more expensive equipment. It is important to remember that the DL1 uses onboard processing that combines GPS and accelerometer data, giving the user a far more accurate output than the raw GPS results shown above. For more information on the range of DL1 data loggers please visit here.

 

DL1 20Hz enhancement option data

So, those were the results of our receiver test, and since we have decided to show you the results we thought it might also be interesting to show how the 20Hz DL1 enhancement handled the same situation. This is a very popular option, the unique GPS technology is nothing short of a breakthrough at this price point and in this respect there really isn't any competition.

The key to the systems performance is in the maths that is used to make the calculations. The 20Hz option (20Hz is simply a measure of the number of measurements that are taken every second) takes the raw GPS data recorded by the DL1 and uses the processing power of the PC to calculate speeds and positions. Typically the 20Hz option won't improve "poor" GPS data, it will however make good GPS data even better.

Remember there is no accelerometer data used to create this data, just the raw GPS and the 20Hz calculations. So the actual output a user would see in the analysis software is even more accurate than this.

In the results above we can clearly see consistent shapes, closer grouping, and the smooth flowing lines the vehicle took around the circuit. Even through the tree-lined sections where the GPS reception was difficult we see clear, concise data. The overall result is excellent (being consistent throughout the whole circuit) outstanding data quality in this typical racing environment. The 20Hz DL1 enhancement option is available on the DL1 CLUB/PRO/WP models.