Jim, I don't know which model Garmin you have, but you can touch the screen in the right spot even when you have a route plugged in and it will switch screens to one that gives speed, along with miles traveled, miles to go, time etc. I'll have to go look at my wife's 660 to give you more accurate instructions as I've gotten used to my 1490T, which works slightly differently....
That's correct - or at least they mustn't read under. So all manfacturers set the average speedo readout above true speed so that production variations never let them go under true.
For the statisticians, I read once that they are allowed less than 3 standard deviations to read under true speed (which would be an intelligent way to define compliance) but I've never seen that again.
Well, as I've noted several times - they don't ALL do it. All BMWs and MINIs might, but I've owned my share of new MBZ, Audi, VW and Jaguars, and they were all pretty much dead on. Likewise my Lexus cars and new Toyota trucks have all been pretty much dead on too.....
You bring up an interesting point Doc. The Garmin can get mph data on its own, but Mark is using the HD device that sends the information to the Garmin via the OBDII port, using blue tooth. Can the Garmin separate what it gets from where?
With just the Garmin GPS you see speed from satellite tracking , if you get it from the OBD via the HD guages you get from the car, which is the same as the speedo. The OBD feed is only seen on the gauges screen.
