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Discussion Starter · #1 ·
Well, I was *so* pumped up about finally getting to use they Turn by Turn feature. We were planning our first trip in the Acadia from El Paso up to the local mountains in New Mexico. I figured it was a perfect time to try out Turn by Turn. I called in to OnStar, told them where I wanted to go. The "Routing.." label was showing on the audio display and then the OnStar Phone rang back. "Sorry, there is a problem with your routes download... not enough cell towers... I'll give you standard directions..." Oh Boy. Well, I already had printed up google map directions (just in case) so there was no use of her giving me verbal directions for me to copy down. Anyway, I told her thanks but no thanks. And off we went... WITHOUT turn-by-turn.

Well, the Acadia performed great for our first longer outing, no complaints there. But now that I realize that you have to have some number of cell phone towers within range, I guess I'm starting to question the use of this system unless you live in a fairly populated areas and also areas WITHOUT local hills/mountains. I didn't realize that turn-by-turn was relying on cell tower triangulation to determine vehicle position. (Well, if that is what they are doing.) Anyway, this will push me to finally purchase some type of portable GPS. It's in these resort/mountain areas that I could use this system the most and trust me, there aren't going to be many cell phone towers on my way to "Bobs Campground in the middle of nowhere".

Don't flame me, I still think this is a terrific, cool feature, but I guess I'm just raising a point that it seems to have some limitations for some people. (There have also been many discussions about why you would by the NAV at all if you can have turn by turn. Well, I certainly just came across a very compelling reason for my situation anyway.)

If you are curious about coverage, you can see a map here: http://www.onstar.com/us_english/jsp/popup/tbt_coverage_map.jsp

Kent
 

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I'm also not impressed by turn by turn. I used it once or twice and thought it was terrible. I was driving East on an interstate and asked to find the nearest UPS store to send a package between where I was and the town I was going. She said OK, no problem and gave me a place ten miles behind me. I called back and said I wanted one on the way, so they sent another one which was in the right direction, but off the highway by more than 10 miles. I wasn't up for a half hour detour, so I called them back. The third try was no better because it 10 miles past where I was going. In the end, I gave up and sent the package from the UPS store near my house the next day.

I really don't like what it does when you go off route (even just to stop for gas). It seems a real pain to start it all back up again, I wish it was smart enough to just recalculate and give new directions from where you are, like my Garmin does.

Needless to say, I won't be renewing my On-Star when the time comes. My cell phone and Garmin do a much better job for my needs. In almost four months, I've never really needed it and the more I use it the less useful it seems to be for me. Maybe if I was older, had health problems or when my daughter starts driving in a few years, I'll change my mind.

I'm also pretty sure the position of the vehicle comes from GPS, not triangulation.
 

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yea, i thought that the turn by turn relied on cell phone towers, The cellphone is powered by verizon (obiesly) and you use teh cellphone towers to talk to anybody including the onstar people ,the only reason onstar uses satilites is when they are unlocking the doors or trying to locate a stolen car, which i thought this morining i almost had to use, because i woke up in the middle of the night (like i have ever since y purchase) and looked in the garage and found the door open and the acadia gone!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!. So i run to the front door and am about to get in the Yukon xl to get to the police station start to back up and i see the acadia behind me (i stopped before i hit it THANK GOODNESS) and i remembered that i parked outside after a movie because the garage floor was dirty and i just cleaned the acadia, the reason the door was open is because of those STUPID sensors and a broom was in the way. But wow was that a scare of a lifetime.

ANOTHER REASON I AM GLAD I GOT THE NAV SYSTEM IN MY ACADIA. Also i went through west virginia and the nav system never lost a signal through the mountains.
 

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Nav systems can be a lot of fun and quite useful. However, they all can have their problems at times. I just got back from a trip where the rental car I used had a nav system. It worked well most of the time, but not always. One time it thought I was driving out in the middle of the lake about 2 miles off of the road I was actually on. It was so :confused:. After a few miles, it finally corrected the positioning. Another time it routed me off paved roads onto a two track dirt road. I was not planning to go 4 wheeling with the rental car on the way to dinner!
 

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Discussion Starter · #5 ·
jseck2 said:
I'm also pretty sure the position of the vehicle comes from GPS, not triangulation.
Well, that was my initial thought also. But the OnStar rep told me something quite similar to "...there aren't enough cell towers near you..". Now obviously I was talking with her via the OnStar system so I had at least one cell tower connection. Here is from a FAQ from MapQuest:
Because OnStar's Turn-by-Turn Navigation service relies on Code-Division Multiple Access (CDMA) wireless data coverage and agreements with carriers to provide this service, Turn-by-Turn routing is only available to customers residing in and initiating or updating a route while traveling through OnStar's contracted carriers' enhanced service capable areas. This covers approximately 98 percent of the U.S. population, and approximately 80 percent of the population in Canada. Click here to view the TBT coverage map

On the other hand, the "How Stuff Works" site says it uses up to 4 GPS Satellites to determine vehicle position. The GPS receiver is called OnCore, and it is part of the VCIM (older OnStar-equipped vehicles have separate modules for the cell phone and GPS system). A GPS receiver uses the amount of time that it takes for a radio signal to get from satellites to a specific location to calculate distance. (For more information on GPS, see How GPS Receivers Work). The OnStar Call Center uses four different satellites to pinpoint the car's location when either the driver or the car itself asks to be located.

Well, so I guess I'm confused. Obviously there are area limitiations based on OnStar's own material. I don't own a handheld GPS, but my understanding is that they work pretty much everywhere unless for some reason you just can't pick up a GPS Satellite. I'm also sure the accuracy of their location algo depends on how many satellites they pick up. Not sure if implement a dead-reckoning algo if you lose all satellites.

Kent
 
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