Last week I took a trip to go Upstate NY to go see relative for the first time since they move there.

I enter the destination on 2 of my Gps C550 and 1450 I take the C550 just for a back up just in case something go wrong on the way with my 1450 both GPS give me 281 miles and about 5 hours driving to get there.

I also enter the same distance on my phone using Waze app. same 282 (it was off by 1 miles) the time was the same.

One thing I Notice while I was driving that the time to reach the destination was off how could be that driving about 50 miles still would require 2 and a Half hour to get there.

Before I left I reset the mileage counter to zero on my car .well when I finally reach the destination the total mileage that I did to reach my destination was not 281 but 377..

Never had this problem before and I wonder how could this Happened on 3 device..

On the Way back the time and Mileage was accurate on all 3 device..

P.S. both Gps are setup for Fastest way.

Straight line vs route.

It sounds like the shorter distance was a strait line distance ("as the crow flies"). Many GPS devices will display the strait line mileage before the route is calculated, then show the actual road mileage after calculating the route. Without knowing the exact sequence of events and what specific information you were looking at, I don't know for sure if that is what happened to you.

Alan - Android Auto, DriveLuxe 51LMT-S, DriveLuxe 50LMTHD, Nuvi 3597LMTHD, Oregon 550T, Nuvi 855, Nuvi 755T, Lowrance Endura Sierra, Bosch Nyon

Keep in Mind

The distance recorded on the GPS is the sum of the distances between each acquisition point, not the actual distance the GPS itself traveled. In most cases, the two are quite close if the GPS has a good "horizon" viewing multiple satellites.

If you could see each acquisition point on your GPS, it would look like a series of dots on either side of the direction of travel. The "snap to" software in the GPS makes the line of travel appear smooth on the screen, usually along the road you are travelling.

For lack of a better way to describe it, think of the route as a straight saw blade. The actual route distance is the end to end measurement of the blade. The GPS acquisition points are the tips of the teeth on the blade. The GPS measures the length along the face of each saw tooth and adds them all together.

Usually the actual distance is quite close to that calculated by the GPS since the "teeth" are very small. On a rare occasion, mostly due to poor GPS reception, interference or geographic anomaly, an acquisition point, or group of them, are way off. I've seen this occur on marine GPS units where a "rogue" acquisition point is off by 50 miles or more. This creates a huge tooth on that saw blade and adds erroneous distance to the actual route.

Sophisticated and expensive GPS equipment used in military, aviation, surveying and marine applications have software that will adjust these rogue acquisition points. Unfortunately, in the interest of keeping costs down, most automotive and handheld GPSr's do not have this capability.

Fortunately, these rogue events are rare but they do occur and are the main culprit in the major mileage discrepancies we sometimes see.

Sorry for the long winded explanation.