Cheap Karting Telemetry!

So…. you can collect your own Karting telemetry on the cheap but you can’t do it for free. In order to get it to work reliably and with consistent data you’ll have to buy a few bits and pieces…. here’s how I do it. This follows on from an article I wrote months ago (First steps in data) but has more info on how I’m actually collecting the data.

Collecting Video

This first and easiest step to collecting data is by using a GoPro. Lots of people already have them and although they’re not always allowed on race day you’re free to use them on practice days although you might have to sign a disclaimer. If you’re hire karting, most tracks will insist the GoPro is attached to the Kart using one of their mounting points or not at all. If you’re lucky they’ll let you use a shoulder mount or even your helmet (which I don’t recommend).

As well as high quality video, if you enable the correct settings the GoPro will give you a GPS path, lateral and linear g-force loadings and current speed which it will overlay on to the video for you. That’s a good start right there. Unfortunately you can’t export this data or do anything with it other than watch it. To go further you’ll need your phone. I’m using a GoPro Silver Hero 7 and it works fine (usually) although I’ve had some problems with it switching off randomly which I’m trying to resolve.

Collecting Data

GoPro, iPhone and GPS receiver all packed and ready to go racing

To collect data I use an app called “Harrys LapTimer” which is available through the app store. I use it on my iPhone XR and previously on my iPhones 7 and 5 without any problems. There are various versions available which give different options. I use the Petrol Head version which was about £20 – I chose that version because it allows me to overlay video. I started off with the Rookie version and once I had it working I upgraded.

Once you’ve got the app installed you need to download a track configuration (a lot of Kart tracks are available already including Bayford Meadows and Buckmore Park (which I submitted) and Lydd (which someone else did). With a bit of care you can set up your own track and once it’s been tested it can be submitted so others can use it. Once the app is working all you have to do is drive.

In order to actually record data the phone needs to be held securely (not in your pocket) otherwise it won’t record acceleration forces properly. For the first few months I had the phone in a holder, strapped to my right leg which worked ok but sometimes meant that lateral acceleration was recorded as linear and vice versa. This was a nuisance so I instead started to mount it on my rib protector in the gap between the two front plates. This proved to be a lot more stable.

A good example of the accuracy and consistency that an external GPS device will give you. This is 2 laps overlaid inside the app

Most phones don’t have particularly accurate or fast GPS systems – for example an iPhone will only record its position once a second which isn’t very accurate for a race track. It’ll also only use one satellite fix which isn’t very accurate either and can mean that your positions are all over the place. When you’re using Google maps the software adjusts your position, moving it to the nearest road. The lap timer app won’t do this and will plot you moving through fields and tire stacks. To prevent this from happening I use an external GPS receiver which records positions 10 times a second and uses multiple satellites to get a precise and accurate position. The device I use is a Dual XGPS150A which I got for £60 on eBay. It connects to my phone over Bluetooth and I wear it strapped to my left ankle. It can be a bit temperamental so I try and let it get a good fix before I strap it to my leg and cover it up.

Syncing it all together

Where all this becomes really useful is when you combine the GoPro footage with the data to get an overlaid video like this one.

An example of what overlaid data can look like – also my first win!

It’s a bit time consuming to do but is pretty simple. The first step is to join the raw GoPro files that make up each race into a single file. GoPros have a max file size of 4Gb and a 10 minute race will span 2 files. I join them together in iMovie but pretty much anything will work. From there I copy the file to my iPhone by dragging and dropping into the Laptimer folder on the phone using the Finder app.

Once the file is copied you can associate the file with the recorded lap data in the app by editing one of the laps in the session, adding the video and setting the end of the lap in the video – it’s a bit fiddly but it works. There’s an option in the settings which can offset the footage and the data – you’ll need to disable it. Once you’ve set one lap up correctly the app will give you the option to set all the laps in the same session from the same video file. After you’ve finished editing the laps you can use the export option to overlay the video. It’ll take a while and uses a lot of space so be patient. Once it’s done I transfer the file on to my Mac and edit it again in iMovie (just adding my logos) before uploading it to YouTube.

Next Steps: Circuit Tools

A comparison of 2 laps around Bayford Meadows in Circuit Tools

Circuit Tools is a free app made by Race Logic who manufacture all kinds of cool telemetry devices for cars. You can download it from their website for free and it allows you to directly compare 2 or more laps from different sessions against each other, overlaying the traces from one lap on to the other while showing the video as well. It’s pretty cool!

The LapTimer app allows you to export data in a variety of formats and one is called “.vbo” which is Race Logics format which Circuit Tools can read. I export the data and send it to myself via email where I save it on my Macs harddrive. Before opening the file, you need to edit it so Circuit Tools knows where to find the video file that goes with the data. Copy the video file that you copied to your phone into the same folder as the .vbo file you want to open. Then edit the file in notepad and change the name of the video file to whatever is listed in the first few lines of the .vbo file. Save the .vbo file and when you open it up in Circuit Tools it’ll have the video set up.

Before you can use the data you’ll have to adjust the “gate width” in the track map section to draw the map correctly. This is because Kart tracks are so small – it wouldn’t be a problem at Brands!

There’s a video tutorial on my YouTube….

And there you go – now all you have to do is learn to interpret all the data you’ve collected and use it to make you quicker!