On 12 Feb, 12:14, Roland Perry wrote:
In message , at 11:52:45 on
Tue, 12 Feb 2008, Anon remarked:

The new digital cameras are going to be set at the normal 10% 0f the speed
limit + 2mph (80mph + and your taking a risk basically)

A true 80mph will typically be over 95mph indicated, so I have no
sympathy for people caught by these cameras.
--
Roland Perry

Perhaps I'm being thick Roland but I don't really understand the point
you're making - how is "a true 80mph" in fact "typically [...] over
95mph indicated" ?!

On 12 Feb, 12:26, Mizter T wrote:
On 12 Feb, 12:14, Roland Perry wrote:

In message , at 11:52:45 on
Tue, 12 Feb 2008, Anon remarked:

The new digital cameras are going to be set at the normal 10% 0f the speed
limit + 2mph (80mph + and your taking a risk basically)

A true 80mph will typically be over 95mph indicated, so I have no
sympathy for people caught by these cameras.
--
Roland Perry

Perhaps I'm being thick Roland but I don't really understand the point
you're making - how is "a true 80mph" in fact "typically [...] over
95mph indicated" ?!

The diference between what the speedomoter reads and the actual speed.
I have a Origin B2 in my car which has GPS speed indication. The
difference between it and my cars speedomoter is roughly 3mpg ...
granted, my car is relaively new and the Germans know precision but
all the same I think 15mph variance is pretty unlikely even with an
Austin Healy rustbucket (but it probably couldn't get to 80 in the
first place!)

David F wrote:

Perhaps I'm being thick Roland but I don't really understand the point
you're making - how is "a true 80mph" in fact "typically [...] over
95mph indicated" ?!

The diference between what the speedomoter reads and the actual speed.
I have a Origin B2 in my car which has GPS speed indication. The
difference between it and my cars speedomoter is roughly 3mpg ...

You appear to be comparing apples with oranges! :-)

Peter Beale

In message
, at
04:26:08 on Tue, 12 Feb 2008, Mizter T remarked:
The new digital cameras are going to be set at the normal 10% 0f the speed
limit + 2mph (80mph + and your taking a risk basically)

A true 80mph will typically be over 95mph indicated, so I have no
sympathy for people caught by these cameras.

Perhaps I'm being thick Roland but I don't really understand the point
you're making - how is "a true 80mph" in fact "typically [...] over
95mph indicated" ?!

Sorry, a typo. I meant 85mph, of course.
--
Roland Perry

On 12 Feb, 12:45, Roland Perry wrote:
In message
, at
04:26:08 on Tue, 12 Feb 2008, Mizter T remarked:

The new digital cameras are going to be set at the normal 10% 0f the speed
limit + 2mph (80mph + and your taking a risk basically)

A true 80mph will typically be over 95mph indicated, so I have no
sympathy for people caught by these cameras.

Perhaps I'm being thick Roland but I don't really understand the point
you're making - how is "a true 80mph" in fact "typically [...] over
95mph indicated" ?!

Sorry, a typo. I meant 85mph, of course.
--
Roland Perry


OK, stupidly I hadn't figured that out!

I've never really used a sat-nav system to compare true speeds with
indicated speeds, so I've never really been aware of the difference
between the 'true' speed I've been travelling at as opposed to the
'indicated' speed.

I guess that implementing a very accurate vehicle speedometer system
is hard to do, so I wonder if most vehicle (and in particular car)
manufacturers design their speedometers "on the safe side", so as to
indicate a faster speed than the true speed - based on the rationale
that it's better for drivers to think they're going faster than they
are, rather than think they are going slower than they are?

In message
, at
05:02:55 on Tue, 12 Feb 2008, Mizter T remarked:
I've never really used a sat-nav system

Do they display a GPS speed? I use a rather older handheld GPS system
(that doesn't have maps).

to compare true speeds with indicated speeds, so I've never really been
aware of the difference between the 'true' speed I've been travelling
at as opposed to the 'indicated' speed.

My current car indicates 60mph at a true 56mph. And similarly pro-rata
at higher speeds.

I guess that implementing a very accurate vehicle speedometer system
is hard to do, so I wonder if most vehicle (and in particular car)
manufacturers design their speedometers "on the safe side", so as to
indicate a faster speed than the true speed - based on the rationale
that it's better for drivers to think they're going faster than they
are, rather than think they are going slower than they are?

They are legally required to. Any error *has* to mean the speedo is
over-reading.
--
Roland Perry

On 12 Feb, 13:44, Roland Perry wrote:
In message
, at
05:02:55 on Tue, 12 Feb 2008, Mizter T remarked:

I've never really used a sat-nav system

Do they display a GPS speed? I use a rather older handheld GPS system
(that doesn't have maps).


I think some do.


to compare true speeds with indicated speeds, so I've never really been
aware of the difference between the 'true' speed I've been travelling
at as opposed to the 'indicated' speed.

My current car indicates 60mph at a true 56mph. And similarly pro-rata
at higher speeds.


Interesting, that's a significant enough difference.


I guess that implementing a very accurate vehicle speedometer system
is hard to do, so I wonder if most vehicle (and in particular car)
manufacturers design their speedometers "on the safe side", so as to
indicate a faster speed than the true speed - based on the rationale
that it's better for drivers to think they're going faster than they
are, rather than think they are going slower than they are?

They are legally required to. Any error *has* to mean the speedo is
over-reading.


I didn't realise it was a legal requirement, but of course it's
perfectly logical that it is. To be honest I hadn't ever spent much
time thinking about it!

Roland Perry wrote:
In message
,
at 05:02:55 on Tue, 12 Feb 2008, Mizter T
remarked:
I've never really used a sat-nav system

Do they display a GPS speed?

TomTom does. It gives lat long as well.

It doesn't give height, though. Is it hard for GPS to be used to determine
height above sea level?

In message , at 14:10:50 on Tue,
12 Feb 2008, John Rowland
remarked:
I've never really used a sat-nav system

Do they display a GPS speed?

TomTom does. It gives lat long as well.

It doesn't give height, though. Is it hard for GPS to be used to determine
height above sea level?

Height is much less accurate than position. It's also of little use to a
driver trying to find his way (rather than, say, a hiker on foot with a
map and contour lines, or an aircraft pilot).
--
Roland Perry

On 12 Feb, 14:10, "John Rowland"
wrote:
It doesn't give height, though. Is it hard for GPS to be used to determine
height above sea level?

A GPS receiver works by narrowing down your position in three-
dimensional space, so figuring out your altitude and figuring out your
location are inseparable.

U

--
http://londonconnections.blogspot.com/
A blog about transport projects in London