nosivad_bor said:
every time i drive across the country these errors become very evident. I driven across the country from PA to AZ about ten times in the past three years. I never count on the GPS for distance it's always wrong.
Yes the unit knows you are going up in altitude but not accurately because it is just a byproduct of the algorithm used to figure out your coordinates. It is designed primarily in civilian models to know you X and Y coordinates, and Z is mainly considered as a side benefit. WAAS and other land based beacons give the GPS a reference point which help it to keep it accurate but it is not as good at altitude as you might think.
A good aviation GPS will have a barometric sensor built in to supplement the GPS calculations.
If you drive the rockies you will find the GPS will frequently be off a thousand feet or more in the mountains.
How is the mileage off? According to Randy McNalley? Your speed-o? Google maps?
Are you sure the GPS is not correct and your speed-o is off due to a different tire?
I really do not understand how a VSS can actually be any more accurate. The VSS is only going to tell you how fast your finial drive gear is turning. It has no idea how fast you're actually going. It's biased on stock tires and gearing. You toss in some 4.11:1 and a 265/75 and your speed-o, and VSS, is basically useless. Sure, it will give you some idea as to how fast you're going, but it's not dead-nuts on.Take the 4mph different and times that by a 2000 mile drive from PA to AZ and who knows what you end up with....
I know for a fact that the garmin is about dead on. I can measure this by the mile markers on the Interstate.
The estimated time of arrival is just that, an estimate. But it's pretty accurate, actually.
I'm also still confused on how the VSS option is "better". I have yet to see a Nav unit say, "in 5-seconds, make a left". The ones I've seen give a distance.
I drive from VA to GA a few times a year. I know that from driveway to driveway, I'm looking at about a 7.5 hour ride, depending on traffic. If I type this destination into the Kenwood/Garmin, it reads 8 hours and 15 minutes. At 65mph, that's probably true. But as you drive, that estimated time of arrival will update. That's true on all units with this feature. So I don't see where the VSS is better in estimated time of arrival.
The GPS software knows the distance between point A and point B. That's how it knows to say, "in 15 miles, make a right onto XYZ Street". It does not need a VSS to do this. The GPS is also going to read how fast you're going and this is typically pretty fucking accurate, as we all know. So why would a VSS improve the actual distance traveled??? The software knows where you are and how far the turn is. The VSS has no clue as to how far up hill or down hill you travel. The only thing the VSS knows is how fast that gear is turning.
