bird_z06 said:
why exactly is the vss not needed?
The unit will navigate with the GPS antenna and will use that data for most of the possitioning and speed and so on. Pioneer also gives you the ability to connect to your car's VSS wire a signal which will pluse at different rates depending on the speed that you drive. This is used when you go into a tunnel and it can't see the sat signal.
It also has built in motion sensors as well for rotation, direction change and a change in positive or negative acceleration. It will use these internal motion sensors too.
If all it had was the GPS antenna and nothing else, as soon as you went into a tunnel it would lose the sat signal and it would assume you just stopped moving, on the nav system it would show you at the entrance of the tunnel. I think they don't actually do that, they assume an average speed and will most likely keep you going forward unless it sees more GPS data eventually.
So the Z1 also has internal accelerometers in at least 2 directions. Front and back and left and right. It uses those to help figure out if you are speeding up or slowing down or changing direction. It can use this data faster than seeing the different in position from the GPS signal.
Finally it also lets you hook into your car's VSS signal (a pulse that changes in frequency as you speed up and slow down). It will watch that line and if it learns a pattern (pulse freq. vs speed it sees with the GPS data) it will start using that to increase the accuracy of your position along with the internal accelerometers and the GPS data.
I didn't know where to look for in my car for that wire and I didn't bother, it's not a necessity. They say it improves your accuracy but I have had very good luck and am very pleased with the accuracy of the position without this wire connected. I guess if you are in NYC or in tunnels where you can't get the sat signal a lot, then it might help. If you are out in the open more than hidden from the sat signal I would think it's not necessary. If you can hook it up, go ahead, it will give you the most accurate and up to date information on how fast you are going. But without it (as long as you get good signal strength from the sat) you will just get a slight lag in the reporting of your speed (might take 1 second to update as opposed to 0.01 seconds). The VSS is only for telling the GPS your speed, nothing more. If it doesn't see that, it will take your position via the GPS and then in a second or so it will take another position, see the difference traveled and the change in time and calculate it. With the VSS it knows instantly how fast you are going.