I have to dispute you on that one John. Some systems have not used GPS... rather a set of accelerometers and sensors that are hooked into the vehicle's drivetrain and deduce location based on their measurements. These systems, although much cheaper than GPS, require you to periodically calibrate your location by verifying it on the map on the display.

 

Brady Brady Brady... not the same thing.... not the same topic..... Not what the rest of us were talking about....
So what "systems" are you talking about? Specifically. Show me one.

But yes, the Ford's have Gyros.
The Ford's have those accelerometers you are talking about.
They do MOST of the moving map work in everyone's FEH's.
They keep the map moving when you are in tunnels and canyons.
( or cities! )

But you still need a GPS fix once in a while.
Even those you are thinking about. Trust Me.
The Ford Nav software only gets a GPS fix a few times an hour.
It is not "every second" like most people think....
And that's probably why the antenna can be buried in a less than optimum location, like inside the dash.
And yes, I am serious.
Check out screen name.
-John

 

As I recall, the basic satellite info comes down at 4 hz. I'd be very surprised if the Pioneer system only sampled at a few times per hour.

I am intrigued by your saying that the Pioneer system has some accelerometers, producing in effect a blended inertial/gps solution.

Thanks,
John Dixson

 

Yea, the built-in NAV system does "dead reckoning" by using the speed senor input and compass direction. So, it will indeed attempt to maintain location on the map even during (brief) GPS signal loss.

This is quite different from my other NAV system. When it looses its GPS signals, it becomes "lost".

Just as a side note, people who cut the speed senor input, loose the "deal reckoning" ability.

 

#1 I have the 2005 which is the same for 2006 and 2007.
#2 This is not the same in unit in the 2008, so I can only speak for what I have.
#3 When you are traveling in a straight line ( highway for example ) the unit only takes a GPS fix every 10 minutes or so.
#4 When you are in the city, making lots of turns, the gyros detect those turns, and the Software requests updates more often... like a whopping one per minute.

I know, this is very slow, but I have actually measured this.
I have a VSS ( vehicle speed sensor ) interrupt button, which allows me to search for gas stations, etc. while in motion. This makes your location icon stand still on the map. The software "updates" to the correct location via GPS fix in 10 minutes if I am going straight, sooner if I am making turns.
A few people have made this MOD and see the same results.

Thus, I always need to look for what I need 10 minutes ahead of time.

 

duplicate post - see below

 

Doesn't interrupting the VSS cause the Odometer to stop counting as well?

Back on topic, it wouldn't be too hard to use the VSS and compass to calculate relative position from a known point (last GPS fix) and then snapped to the nearest roadway. I guess it could get a bit confusing if roads are close together like frontage roads or small developments or times when the compass might go crazy (high voltage lines?).

I wonder what the advantage of having a longer refresh rate is. It's my understanding that GPS receivers don't' use much energy. I can't see where taking quicker GPS samples would be less processor intensive than having to do the VSS/Compass (or gyro) projections.

Long ago I used USB powered GPS for my laptop and it sampled rather often (had to because it didn't have VSS, compas, or gyros) and obviously didnt' use much power.

GPSMAN1, do you have more insight on GPS power requirements and standard refresh rates on portable units?

 

The power use is low compared to your car, but pretty significant to a couple AA batteries in a hand held. Refreshing as you put it, less often in a hand held will make your two AA batteries last 24 hours vs. 12 hours.

I think the car gets GPS fixes infrequently because this allows them to put the antenna in a very poor location so that they can keep it invisible to the owner.

Antenna position is pretty important with those portable units that sample once per second. With a poor antenna, it make take Ford a whole minute just to get one accurate "fix" on your location.

Oh, I only interrupt the VSS on the back of the radio, with has no effect on the rest of the car!

 

The GPS described here must be quite different from the GPS in my PDA/Phone!

 

Much better. I wondered how the ECU would feel about losing that information as I'm sure it's used in some of the calculating.

I also wonder if this would work to allow a passenger the ability to put in a destination on the fly. As it is now on the '08 NAV , you either have to be stopped or have an address in your address book to input a destination. (I understand not letting the drive do this while in motion but why not a passenger? Maybe link it in with the passenger airbag sensor? )