Fast updating (20Hz) GPS receivers for motorsport track mapping?

[Chris Wilson]

I run a Motec mappable engine ecu on a couple of circuit race cars. This ecu accepts an input from a GPS receiver, and logs the co ordinates in memory. A data analysis package from Motec then draws a track map showing the cars position and a GPS speed etcetera. I currently use a 5 Hz Garmin receiver called a GPS18x-5Hz the technical spec is in this Garmin paper:

http://www8.garmin.com/manuals/GPS18x_TechnicalSpecifications.pdf

Motec charge a fortune for this obsolete Garmin unit that they sell ready terminated in a Motec box, I purchased an unadulterated Garmin one from Ebay for 1/3 of the price and just put a Deutsch connector on it, and it worked fine straight out of the box.

Motec also list faster updating receiver units, these being with a separate antenna to the receiver itself, the best of which seems to be 20Hz, see screenshot of catalogue page at:

http://www.gatesgarth.com/motec.jpg

These are extraordinarily expensive, being £1200 UK pounds, about $1940 US Dollars. Given I am doing this as an amateur, on a tight budget, could I purchase something that will work the same, maybe not in a nice die cast box, and save myself a lot of money? Can anyone suggest devices to investigate that will communicate by RS232? I doubt I can get or work out the Can Bus info to read a GPS Receiver by that means. I can probably get more info on the protocols the Motec ecu expects, they have a webinar on using GPS that explains this, but the little self contained Garmin GPS18x-5Hz worked fine "as is" by RS232.

Thanks for any help here.

 

[ianh]

I'm not sure if this is that helpful but I've got a "hobo" version of what you're after on our rally car. I use a £50 Bluetooth 10hz GPS receiver (Qstarz BT-818XT) which can be linked via a BT to a £60 RS232 adaptor like this - http://www.blueunplugged.com/Mini-Bluetooth-Serial-RS232-Adapter.aspx

For uber cheapness mine is linked via BT to the Racechrono app (free) on a Nokia N95 (free). Then another free program Racechrono2avi converts it to track map, speed, "G" force, lap times, split times, trap speeds etc whcih is fully customisable and can be overlaid onto a video track and the best part is it's almost free apart from the GPS receiver.

Ooo and at 10hz it's accurate to 0.03 of a second and I've personally tested it to 155mph which should be enough for most circuit driving!

EDIT here's some footage overlaid on our rally car during a shakedown run to see what it'd look like when we do it properly at the next rally. The background can be made transparent, the map made bigger/smaller/overlaid onto aerial picture etc, it's fully customisable (like a free version of Trackvision/TSX etc).

Watch it in Fullscreen to see all the detail (720p vid)