Talk Morgan Forums Morgan Sports Cars Morgan Plus Four, Supersport & Plus Six (CX & CXV Generation Vehicles) Have you driven your CX today?

I sometimes use the "Sygic" app - some nice navigation stuff, but also a "HUD" which can be inverted if you want. Also it will warn of upcoming sharp bends, speed limit changes, and if/when you are over the limit!

I just ordered a GPS speedo. Two reasons for this, the first is that the Plus4 speedo is buried under the tonneau cover, on the rare occasions I'm out alone with the passenger side covered.

The second reason is that my dashcam flips into GPS speedo mode as I approach speed gantries, and I find that to be far more accurate than the car speedo. However my dashcam doesn't always trip on the gantries, it seems to be more consistent at night, which is odd.

Aaah. I have the Sygic app already but never used. Hadn’t seen the HUD bit with the speedo so am defo going to give that a go. Ta for all ideas
HB

I have never been sure how accurate GPS speed is. The raw satellite signal is a time signal. What the gps is doing is finding your location from the time signal of several satellites, leaving a short time lapse and then locating you again. Your speed is distance between the tow locations divided by the time gap. So there are three obvious sources of inaccuracy - the locations ( typically to 2m radius on my marine GPS at best) and the time ( which is pretty good). You then need to add in atmospheric effects , signal delays etc so you end up with a combination of errors. Over a longer time interval the speed will be more accurate than a short time interval.

Wouldnt worry anyway. The thresholds on most speed cameras are pretty generous. An old friend ex plod who was the traffic man covering the Avon motorway bridge for some time set the threashold there at 20 mph above the limit because and less than that used to flood them with cases. I suspect its the same over here because drivers have been ignoring the permanent 50 on the smart motorway for years and the message would have got out by now if it was anything like 55 or 60.

Mine's slightly different, it's an HUD that runs off the OBD2 socket, so it powers up when you switch on, I only have speed displayed but it can show, RPM on the long arch sweep you can just see in my original post, as well as coolant temp, volts & other stuff

Of course it over-reads by a few MPH (as it's the ECU speedo feed) but at least you are camera safe, if you're a bit tech savvy you can get into the menu and tweek the % addition to say 105% so will be closer to a nav accuracy

Typical commercial GPS devices are accurate to 4m with a 95% probability according to most makers. So that means over a mile (1600m for the mathematically lazy like me). That means .25% as a guide. That's not going to be material to a discussion with a speed camera notice! It's also likely to be more accurate than the car's built in system given the range permitted. Given the average speed cameras are over multiples of miles the GPS is going to be way more accurate than you need to get nicked

I would hesitate to say that the latitude on the cameras is of that order. In a 20 or 30 limit they are set quite tightly from one of the speeding re-education courses I may have once attended. Allegedly.

I was using the Sygic "HUD" recently, and it looks like the speedo in the Honda reads about 2-3mph higher than the GPS.

Thanks for that Jon- v useful to know. Do you fix your phone in place using a Velcro backing or something similar?
HB

In my Plus 4, I actually used a double-sided adhesive strip to stick an old iPhone to the dash to the right of the steering wheel. As I am currently "between Morgans", I am forced to drive a Honda, and a clamp on one of the air vents gets the phone closer to eye level!

NB - the adhesive strip I mentioned was very strong, but it came off completely cleanly before I sold the car.

Brilliant- thanks old chap
HB