AH64ID wrote:
GoPackGo wrote:
If you have a GPS that reads out MPH, set your vehicle speed at 60 mph as shown on the speedometer and compare to what the GPS says. The GPS should be accurate. If I remember correctly, My GPS says I'm actually going 63 at an indicated 65 on my speedometer.
I have yet to see a vehicle where the speedo and odo match, meaning if you adjust/learn your error based on the speedo the odo may be wrong.
I personally prefer to reset the 2nd trip meter and gps while stopped then clock a difference over a long easy drive. My old tires were within 0.3%, and the new ones look to be within 0.5% but I need another drove to verify them. My speedo reads close, but it doesn't read the same as the gps speed.
I've observed this difference with 4 different vehicles now using the same Tom-Tom and here's my thoughts? Again, this goes back to the hills vs flat theory.
The GPS in the Tom Tom is getting the speed from the sky, looking down. Granted, it might be getting the signal from 3 to 7 satellites, but it's still from "above" looking down. From straight above, a vehicle traveling up or down a hill will appear to be moving at a different speed, than the actual ground speed.
Like I said, I've seen this discrepancy in every vehicle I've used my Tom-Tom in.
My current truck is interesting. It has an actual needle type speedometer. It also has a digital speedometer. And I use the Tom Tom. Funny, that the three are never exactly the same, only very rarely are they exact, and I've noticed that is only on very flat ground. So, I come to accept this as the norm now.
When planning a trip, Tom-Tom shows the miles and time. I use this as a guide, not a fast rule. Traffic delays, detours, rest stops all add time. The secret in planning is to determine a comfortable driving distance, say 200 miles a day. And if you drive that in 4 hours, or 10 hours, well ... if 10 hours ... you must have stopped and smelled the roses! That in itself is a good thing!
