Accuracy of the RNS510

[Sharkie]

I have a RNS510, retrofitted, and sometimes the position on the road and on the Nav map can be 100m out .... ie, on the Nav, I'm 100-150m away from an intersection that I'm actually waiting at on the road .... and sometimes it has me driving down a parallel road on the Nav instead of the road I'm actually on ....

How accurate are these things?

Does the antenna position and the number of satelites picked up affect the positioning that much ?

[Pepe]

Yeah, that's a bit weird... I don't have that problem with mine, but I have a factory fit which uses the roof aerial. Occasionally it'll get the wrong road in the CBD and think I'm in the Cross City Tunnel when I'm above ground, but that clears up real quick when I start moving.

[Maverick]

I have a RNS510, retrofitted, and sometimes the position on the road and on the Nav map can be 100m out .... ie, on the Nav, I'm 100-150m away from an intersection that I'm actually waiting at on the road .... and sometimes it has me driving down a parallel road on the Nav instead of the road I'm actually on ....

How accurate are these things?

Does the antenna position and the number of satelites picked up affect the positioning that much ?

GPS accuracy is affected by many factors including

atmospheric conditions (overcast/raining especially)
rf interference
satellite positions at the time
trees, buildings and so on
type of gps system used (there are more advanced types like differential GPS that measures the distance from known land based objects - for example WAAS achieves accuracy of 1m horizontally and 1.5m vertically in the US)

Generally you have an accuracy of around 10m and depending on the number of factors about it can blow out to 50m or more.

The number of satellites the car can see is critical, 2 is just usable, 3 will give you altitude (most of the time) whereas 4 or more are best.

Your car also keeps track of where it is when it loses signal so going into a car park or other structure where the signal is obscured will see it use data like steering angle sensor, speed and so on.

Generally after you've been on the road for a few minutes it will be accurate, sometimes you may need to reboot the unit (rarely) and the version of software can have an impact on it's sensitivity.

The data for the maps isn't aways accurate either, Sensis/Telstra do a poor job with the mapping data so errors from that are not uncommon.

The antenna position can play a role and mounted on top of the roof as per the factory location is the best however it's a PITA to put it there plus it's expensive as the roof antenna is a few hundred dollars plus painting plus pulling the car to pieces to run the cable. Under the dash at the front is generally a pretty good spot.

[ian]

I installed mine a few weeks ago with a magnetic GPS antenna fitted under the dash and ive found that its very accurate , like when i stop at a intersection it shows i'm there ,spot on .

What version are you using mines version C weather that makes any difference i don't know?