Inaccurate Navigation System

No problem like that with our NAV system. Are you getting a good fix with the satellites?

Tom

 

rpa,

Welcome to PriusChat.

I noticed a similar condition this past weekend. I use the GPS maybe once a
month. But, I was out of town and needed some guidance. At one point,
when I was stopped at a corner for a light, the pointer showed my being I'd
guess 100 yds short of the corner. It stayed that way until I turned the
corner, and then it immediately caught up. I didn't see this again, but I
confess, I wasn't watching closely. I don't keep the map screen up for a long
time as Id rather have the energy flow arrows immediately available.

I'm going to have to do some quick checks tomorrow and see if it was one-
time, or on-going.

 

The Prius nav uses both GPS and dead-reckoning. It uses it's last position and any turns made and the distance traveled since then to guess where it is, then moves the map to center that location. GPS helps, but on parallel or slightly angled roads, it can get confused. Also, my nav went wacko during sun spots once from bad sat signals.

If you're in a city with tall buildings, GPS can be spotty so dead-reckoning takes over and can be dead wrong. If the display is mostly right, zoom in to maximum and calibrate (it's in the settings). Drive around a block in the suburbs (good sky view, good turns to compare to the map), stop and put the car in Park, and start playing with the calibration until the map is aligned with the real world. Your indicated position stays in the center of the screen, but you can pan the map in any direction and even rotate it, so you are pointing along the street you are on.

 

What you are describing is not the accuracy of the GPS, but the accuracy of street addresses. Since your current location tracks correctly and POIs work properly, we know the navigation is working and you are getting a good fix from the satellites. This comes down to how mapping software deals with street addresses. The mapping database on any system doesn't actually have a table with every street address. Instead they use end-point addresses for every street. If one end of a street has the address 1600 and the other end 1700, then 1650 is assumed to be in the middle. This works well in some areas, and not so well in others. For more complex addressing, more hints are added to the database. I suspect the addressing database isn't all that great in your area. Ours works well where we live, but I have been to other areas where it's off a bit more.

Tom

 

I believe the tracking may try to estimate that you'll be in front of the location by the time it stops talking based on the speed it believes you should be going for the type of street you're driving (residential, freeway, etc). This is only a guess on my part. The reason why I say this is I've been annoyed as well about this and my other cars with factory GPS do not do this (so the addresses should be accurate). In addition, when I hit the button on the steering wheel while driving with the map up it does in fact give me a pretty accurate street number when it refreshes. The last reason why I believe this is the case is because mine will tell me, "you've arrived at your destination" and I'll still see the colored route on the screen where I obviously haven't reached the marker on the screen yet. So it knows, (or at least the marker on the screen) I'm not actually at my destination, even though it verbally tells me.

Mike

 

I'm still using the older version. I haven't seen anything compelling to make me upgrade, but the jury is still out.

Tom

 

This is definitely what I call the "theoretical address" problem. All my GPS units have had this to some degree in some areas.

The Toyota NavTeq based maps definitely have it somewhat worse than the Garmins I have. But, it's manageable and not that big a deal if you are aware of it.

 

Agreed. I look at all address destinations as approximate.


Tom

 

I guess I'm the only one who's GPS is virtually 100% accurate? It's only the voice that seems a bit premature announcing arrival.... but the waypoint is right on.

 

The East Coast (Harrisburg, B'more, Philly, DC) cities I drive in are notorious for the deviation between the City Planning maps and reality on the street. There is one street in Harrisburg where the addresses on the buildings seems random. I know you'll think I'm exaggerating but there are literally odd and even addresses on the same side of the street. Needless to say GIS systems' idea of the addressing scheme doesn't resemble the reality.

If you don't have the issue, it's because your area better approximates the planning maps.

 

The calibration function (in the settings) calibrates the dead-reckoning hardware. It's good to do this now and then, especially when you change tires.

The voice system says "You have arrived..." about a half block before you reach your destination. A bit later it says "Your destination is ahead on the right..."