psteng19

Does anyone have a definitive answer?

I was stuck in traffic at a spot where I would generally be home in 10 minutes tops if moving at posted speed limits.
The other day, I was stuck in crawling traffic and the nav's ETA was 19 minutes.

Reach

My experience was similar. It was scary accurate with its time estimates, didn't matter if I was doing 85 on a 5 mph on a 55 mph highway, it seems to provide good estimates based on actual speed.

visuelz

My Garmin Nuvi, knows exactly how fast I am going variably so it know the exact time I will get somewhere.

cestmoi

Ditto with my TomTom GPS 510. It will recalculate the arrival time and it's usually VERY accurate within 1 min.

MrChanh

once i hit 140 in my tl then it says that it leads me to my destination in 00:30. haha jk. my stock navi is pretty close. down to 1 min

acn684

most navi's are pretty accurate, however some of them don't factor in speed limits on some parts. I had my navi tell me 5 mins on a 5 mile road which had a posted limit of 25 mph.

cestmoi

I think this is moreso because of the fact that the stretch of road was probably either new (new to the map you have installed at the time) or that they changed the limit and your Navi doesn't have the data of the new PSL.

I'd like to hear what brand of Navi doesn't have accurate arrival times. For example, I've been looking hard at the Navigon, due to the lifetime free traffic, but hesitant in getting it as the re-routing feature sucked balls from what I see in many user reviews.

cestmoi

Wait, I just thought of something... I think your Navi wasn't wrong... for it to tell you that you'll arrive in 5mins over a 5 mile stretch, you must be travelling over 60mph at the time!

SoCaliTrojan

I know that if I'm stopped at a red light, the ETA clock freezes (IE: it just measures the amount of moving time). I also notice the ETA change when I hit traffic (takes a couple of minutes though).

Navi's can use your gps coordinates to calculate how fast you're going, but they can't tell when you'll be stopped by a red light. As long as you're moving, I think it'll continue using available information to make new calculations...

Tsx536

Many Navigations also use the VSS vehicle speed sensor to determine how fast you're going. This sensor sends out X amounts of pulses per second based on how fast you're going.

The factory navi has a VSS output from the ECU. I learned this when having to insert a VSS wire into the ECU harness to get a VSS signal for my aftermarket navi.

I'm guessing the ETA is calculated on some algorithm that uses a combination of your current speed and the speed limit of each street you'll be traveling on during your route. The GPS is probably constantly polling the sensors and updating the ETA. I wonder how much more accurate the ETA is if you have NavTraffic

t_in_maine

I've found that when I'm going on longer trips (6-12 hours) my Nav. starts off with very wrong arrival times. It does evenutally recalculate, but sometimes not till I'm within 200 miles or so of my destination.

cestmoi

I'm just curious as to how you'd know that the arrival time is wrong? Wouldn't be surprised that the GPS can be off sometimes because of new roads/changed posted speed limits, etc.

black label

It definitely can take speed into account. If you lose the GPS signal, it uses the speed and gyroscopic sensor to "try" to figure out where you are and leaves "electronic bread crumb" of where you've been.

How long it takes to update ETA is another question.

t_in_maine

Because I've been to my brother's house in CT a ton of times, and when it tells me that it's going to take 10 hours and I know damn well it takes 8, obviously it's wrong. I still calculate the route just in case I decide to get off the highway for meals, gas, etc., I want to make sure where I'm going to get back on.

cestmoi

That 10hrs, I'm assuming is at the beginning of the journey, how about when you get closer? Is it still wrong?

itsme27

I like to play a game with the ETA, everytime I look over and it says I have x amount of minutes remaining. I always say "i'll show you" and try to beat it. But I always loose.

I think the ETA is pretty accurate when it readjust itself to the way you are driving, and the conditions around you. But obviously you have to keep checking it, and comparing it against the actual time that is measured in the dashboard.

On that note, Everytime I turn the car off the timer in the dashboard resets itself. Is there anyway to tell it to keep counting the time? It would be a useful features with trips that are long distance.

t_in_maine

As mentioned in my first post (I've found that when I'm going on longer trips (6-12 hours) my Nav. starts off with very wrong arrival times. It does evenutally recalculate, but sometimes not till I'm within 200 miles or so of my destination.)

Yes, it does eventually recalculate to the correct ETA, but it is sometimes wrong for probably 75% of the trip.

Tsx536

^^ Hmm...it's off from 75% of the trip? Will it make a big change in ETA at times? Like go from 3 hrs ETA to 2 hrs ETA? That does seem like it's updating a little slow.

slfmade

I've found this to be very true for my 2004 tsx as well. I've driven from kansas city to tuscaloosa, tuscaloosa to miami, miami to panama city, and panama city to saint louis. all are similar distance trips, about 750-850 miles which google calculates to be around 12-13 hour trips. when first type in to my navi kc to miami was estimated at around 20 hours or so, this was similar to all the other trips as well and found that it gradually got more accurate the closer it was but was significantly innacurate at the beginning which has always led me to wonder how it calculates that exactly

after reading the rest of the thread it does not make huge changes during driving, it is gradual maybe knocking off 75 minutes during a 60 minute period, nothing really too big that is noticeable

mltk53

ditto