How speed limited is "100 speed limited"

Oh, oh, Can I tell you about when I was doing engineering and using
theodolites and the like.......?

Hammo

 

Well, even if there is a stepper motor in there, there's still the
question of coming up with an accurate way to come up with a position
to turn the stepper to.

Repeatability is one thing - something that should be very easy with
a stepper motor (and more difficult with other 'analogue' techniques).
Accuracy is another entirely different ball game.

A lack of accuracy in the measuring bit, and the most accurate/
repeatable meter mechanism in the world is no good. A lack of
repeatability in the measuring bit is probably even more worserer.

GB

 

Ah, ok, if we're talking about stuff like that, then yeah, go for
your life, run the dumb bastards over - I'll hold 'em down for you
if you like!

Er, now I think you ought to be grateful that they've bothered to
put their "thank-you for letting me in" light on *before* they've
assumed their god-given right of way!

Amen brother!



On a similar theme, I pulled the Thunderace to bits and found a
space big enough to fit twin air horns the weekend before last.
The horns are good - cars that decide to help themselves to your
space **** off back to where they came from, even managed a look
of sheer terror (priceless!) on the face of a dopey woman who
flicked a cab door open in front of me in the city on Friday!
Driving the car around today though, there were an inordinate
number of morons out and about, and damn I missed those horns!


GB, horny.

 

GPS is particularly bad at knowing where it is (with any degree of
accuracy) when its standing still or moving slowly. When you're
moving relatively quickly, its much easierer to come up with good
speed and direction figures, and so accuracy will improve.

I think that, in principle, what you're saying about going around
corners must be right, but if you're using the GPSr to check the
speedo, I'd like to think that was happening in a straight line
ad a reasonably constant rate of knots.

That said, it's important to note that pretty much all modern GPSr's
are 12 channel jobbies - means they can tune 12 different
satellites simultaneously - but they only need four satellites
to get a position fix (I'm not sure why they need the fourth,
but they do - might be the altitude thing, but then they're notoriously
bad at altitude, being designed for position-at-sea-level performance).
Accuracy improves with each extra satellite it manages to tune, and
in my experience, 7-9 satellites at once is typical, giving a nominal
positional accuracy of 3-4 metres.

The things typically *report* their position (or update other
numbers like speed, direction, etc) every second. I'm not sure
that they only *know* those numbers once per second though. I'd
expect that the numbers that they deliver once per second are
aggregates. I don't *know* but.


GB, geek.

 

You certainly can. Go for it.
---
Cheers

PeterC [aka MildThing]
'81 Suzuki GS450-s (gone on to better and brighter things - I hope)
'87 BMW K100RT (write-off)
'81 Yamaha Virago (XV) 750H (work in progress)
'01 Yamaha FJR1300

www.dmcsc.org.au
http://eladesom.com.au/ulysses/
# 37181

 

I don't know... I'm not tasmanian so I don't have a front sprocket


G-S

 

I wouldn't argue with that... I do find it hard to understand how the
same organisation can end up with 2 such different cultures around thier
vehicles though!

G-S

 

Eh? It's very bad at knowing which way it's pointing, but
it knows where it is just fine. And what time it is.

-----sharks

 

Your reflexes will be razor sharp.

Postman Pat

 

It knows where it is more betterer when it's moving. It's
pretty good at knowing where it is when it's in the same place
it was before.

It's *great* at knowing what time it is. It knows what time
it is to within a poofteenth of a what, whether its moving or
not!

GB

 

That's what the Sigma Sport Targa pushbike speed computer is for

Mark.

 

Well, you said that before. But why? Nothing I know about GPS,
and nothing I've seen using one, suggests that this is true.

-----sharks

 

And that's important to you? As long as my watch is within five or ten
minutes, it's near enough for me. Of course, if I don't have an urgent
appointment, Tuesday is near enough.

Theo

 

Using them for Geocaching, (http://geocaching.com/) when you're
trying to push the receiver to the limits of its accuracy, I find
that making several moving passes past the point where the goodies
apparently works more betterer. If you only care about where you
are to within, say, 25 metres, it wouldn't be an issue.

GB

 

The one in the car in Germany was a bit confused when we were barrelling
down the autobahn. Mind you, the signs were a bit blurry too.

 

<applause>

Moike

 

Looking like Clem, you've got to be able to take a joke!

-----sharks doherty

 

Most use a voice coil, the same as a hard-disk.
They are as accurate as the manufacturers want them to be, and there's no
variation between speedo units, but since each tyre has a different
circumference (particularly as they wear), and the speedo pickups are from
the final cog in the gearbox, your speed gets more and more optimistic as
your tyre wears out

It's a common trick in the UK for cabbies to overinflate their tyres when
they go to have their meters calibrated, then they put them back to normal
to make them register in their favour. Of course, I'm sure they wouldn't do
that here in Australia, as it's unsporting

Cheers,
Jason