Choosing the right GPS for your application might sound simple, just choose the one with the fastest output rate. Unfortunately, it is not so simple and is actually quite complicated. In this article we'll try to guide you to select best one for your use case.
When choosing the right GPS, environment where it is used is actually the most important criteria. 50Hz GPS is the right choice ONLY when there are no obstacles like trees, buildings or large hills. 50Hz is not the right choice for rally, hillclimb or any other racing when used in poor coverage and obstacles. Reason for this is that the amount of accumulated data is small from which the solution (Speed, position etc...) is calculated. All buildings, trees and other obstacles will show in the data as a large drops or spikes in the data. Surely, data could be averaged but then the advantage of the fast GPS is lost. Also, signal has to be strong, above 40dBi for the 50Hz device to work well.
Below is an example to illustrate the difference between 10Hz, 20Hz and 50Hz speed outputs. Test route is next to tall buildings.
Cursor location has a sudden spike in the 50Hz GPS speed output and is an area with houses next to the road. Outputs from 10 or 20Hz devices do not have these spikes because it has more data from longer period to calculate and average the speed.
These drops or spikes in speed make comparing laps very difficult and data is almost unusable.
To illustrate this further, below is a test with 10Hz, 20Hz and 50Hz GPS's measured during the same test route. Yellow, 50Hz has spikes and in general is noisier than others due to smaller amount of accumulated data.
So, how to select the GPS?
Use following guideline to select your device:
|Environment has trees buildings and other obstacles||Best||Good||Poor|
|Stable speed output is desired||Best||Good||Poor|
|Fast performance with low latency is required and used in open sky.||Poor||Good||Best|
|Motorcycle racing application with high lean angles||Poor due to high latency||Best||Poor|
If you need fast performance for launch control, 50Hz can't be beaten. But, 20Hz isn't much slower and might be actually the better choice considering all factors.
Contact US if you have comments or questions about choosing the right GPS.