Hi I am putting together a system to compare two vehicles position for timing around a race track. I see most of the GPS modules are accurate to 3 metres or so. Do you know of or are able to get in GPS modules that are much more accurate? 50cm would probably be ok but smaller would be better.
I’ll be using it with the Omega2 so should be able to use usb, serial or i2c no problems.
Thanks!
Hi Josh, I’d recommend you build your project with regular GPS devices. The accuracy they publish in their specifications is a “best case scenario”. Most GPS devices need an unobscured view of the sky and time to lock on to their position. So you might find the most important things affecting GPS accuracy are things like:
- trees overhanging the track
- powerlines over the track
- track runs through a valley or cutting
- GPS antenna is blocked by part of the car
This image is from a recent bike ride of mine. I went up and back on the same track that was about 2m wide. Because of the tree canopy above me, the GPS’s accuracy was affected. Sometimes it looks like my up and back rides were more than 10m apart!
One of the data values you’ll get from the GPS devices is it’s own “accuracy”. It will tell you its accuracy every time it outputs data. In perfect conditions it might say accuracy is 1m. If its unable to see enough GPS satellites it might give accuracy as 100m, or worse. Your project will still benefit from high quality GPS devices. But even the best ones will lose accuracy as there is more interference around them.
Please post up your project when its done. We’d love you to show it off!
- Chris
To add a little bit to what Chris said, if you have a clear view of the sky 3m accuracy is still very accurate! The average drone or UAV is equipped with GPS antennas that are no more accurate than this. Again assuming there is a clear view of much of the sky, they are able to typically navigate with what appears to be less than 3m of error.
If you are talking about full size vehicles on a racetrack, I think you would find that the errors in accuracy would average out to still give you really good readings overall. If we are talking about model cars on a small track, then this may not be accurate enough to give accurate speed readings.
Thanks guys for your info. I will continue with the project and test it out to see what I get. I’ll likely go for a more accurate device once I get some data. I see that the official gps module for the Omega2 status 1.8m accuracy. We are using regular sized vehicles and a race track usually has quite open areas for run-off etc so will have a good look at the sky.
I’m thinking that an external antenna might be the way to go as it should increase the number of satellites it can see, and lets us put the antenna in a good place, perhaps even on the bonnet.
We are hoping to be able to get relatively accurate lap times, but I guess when you calculate it 3m is 0.05 seconds at 200km/h so we could state 0.1sec accuracy at highway speeds.
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Also keep an eye on the Galileo system. I’m not sure what the global coverage is yet, but they say that it will be fully operational in 2020, so it may be useful if this is going to be a long term project. Using the public version, you can get down to 1m accuracy, and for commercial purposes that can be lowered down to a crazy 1cm!
And just on antenna mounting, be careful if you’re planning to use magnetic mounts on the outside of the car, as the air rushing over may rip it off the car. Also don’t cover it with carbon fibre, it’s very conductive and will stop quite a lot of the signal getting through, I’ve been caught out by that before 
