|
Cellular forums Home > Archive > GPS > February 2007 > How acurate is the speed measure?
You are viewing an archived Text-only version of the thread.
To view this thread in it's original format and/or if you want to reply to
this thread please [click here]
| Author |
How acurate is the speed measure?
|
|
| Razzle 2007-02-22, 10:33 am |
| I have been using my Navman icn720 for a couple of weeks now. I am not
convinced that it is such a great unit, the map accuracy leads a lot to
be desired in the rural area that I live, but I can put up with a littl
of that.
My main concern is that when I am travelling along, my speedo says one
speed, and the GPS another. Who should I believe?
The GPS is as much as 10kmph slower than my speedo. Which is great if I
have been always under the limit, but I do not want to push my luck and
drive at the GPS speed only to get tickets.
What device should I believe, the GPS or my Cars Speedo ????
| |
| claudegps 2007-02-22, 10:33 am |
| On 22 Feb, 13:39, Razzle <our...@dcsi.net.au> wrote:
> What device should I believe, the GPS or my Cars Speedo ????
GPS.
Your speedo must not show a speed lower than the real... so it shows a
higher speed.
Claude
www.claudegps.altervista.org
| |
| Jim Townsend 2007-02-22, 10:33 am |
| Razzle wrote:
> I have been using my Navman icn720 for a couple of weeks now. I am not
> convinced that it is such a great unit, the map accuracy leads a lot to
> be desired in the rural area that I live, but I can put up with a littl
> of that.
>
> My main concern is that when I am travelling along, my speedo says one
> speed, and the GPS another. Who should I believe?
I would trust the GPS over my vehicle speedometer. It's not uncommon
for car speedometers to be wrong.
If you've changed your tires to a larger or smaller size, you can
expect your speedometer to be off.
Larger tires will cause the speedometer to read low, smaller tires
will make it read high.
| |
| molecule.lee@gmail.com 2007-02-22, 10:33 am |
|
Razzle =BCg=B9D=A1G
> I have been using my Navman icn720 for a couple of weeks now. I am not
> convinced that it is such a great unit, the map accuracy leads a lot to
> be desired in the rural area that I live, but I can put up with a littl
> of that.
>
> My main concern is that when I am travelling along, my speedo says one
> speed, and the GPS another. Who should I believe?
>
> The GPS is as much as 10kmph slower than my speedo. Which is great if I
> have been always under the limit, but I do not want to push my luck and
> drive at the GPS speed only to get tickets.
>
> What device should I believe, the GPS or my Cars Speedo ????
GPS should be more accurate, becaure the speed is figured out by
Doppler frequency shift.
| |
| molecule.lee@gmail.com 2007-02-22, 10:33 am |
|
Razzle =BCg=B9D=A1G
> I have been using my Navman icn720 for a couple of weeks now. I am not
> convinced that it is such a great unit, the map accuracy leads a lot to
> be desired in the rural area that I live, but I can put up with a littl
> of that.
>
> My main concern is that when I am travelling along, my speedo says one
> speed, and the GPS another. Who should I believe?
>
> The GPS is as much as 10kmph slower than my speedo. Which is great if I
> have been always under the limit, but I do not want to push my luck and
> drive at the GPS speed only to get tickets.
>
> What device should I believe, the GPS or my Cars Speedo ????
GPS should be more accurate, becaure the speed is figured out by
Doppler frequency shift.
| |
| Stephan Robotta 2007-02-22, 10:33 am |
| Jim Townsend <jwt@nota.realaddress> wrote:
>
> If you've changed your tires to a larger or smaller size, you can
> expect your speedometer to be off.
This is the main (and only?) reason why a car speedometer needs to have
a tolerance i.e. display a higher speed than the actual speed that you
are driving.
Stephan
| |
| Marc Brett 2007-02-22, 10:33 am |
| On Thu, 22 Feb 2007 23:39:55 +1100, Razzle <ournet@dcsi.net.au> wrote:
>What device should I believe, the GPS or my Cars Speedo ????
Wise man (well, Sam, at least) say -- A set of measurements is worth a thousand
expert opinions!
Find a measured mile and a stopwatch and drive it at a constant speed. Post
results here.
| |
| TheClyde 2007-02-22, 12:33 pm |
| > > If you've changed your tires to a larger or smaller size, you can
>
> This is the main (and only?) reason why a car speedometer needs to have
> a tolerance i.e. display a higher speed than the actual speed that you
> are driving.
I have read that even the normal wear on a tire tread will cause the
spedometer to be off as well.
| |
| Amos Soma 2007-02-23, 10:33 am |
| My Tom Tom One is always about 1 to 2 MPH faster than why my car speedometer
says.
"Razzle" <ournet@dcsi.net.au> wrote in message
news:45dd8f1c$0$1146
$61c65585@un-2park-reader-01.sydney.pipenetworks.com.au...
>I have been using my Navman icn720 for a couple of weeks now. I am not
>convinced that it is such a great unit, the map accuracy leads a lot to be
>desired in the rural area that I live, but I can put up with a littl of
>that.
>
> My main concern is that when I am travelling along, my speedo says one
> speed, and the GPS another. Who should I believe?
>
> The GPS is as much as 10kmph slower than my speedo. Which is great if I
> have been always under the limit, but I do not want to push my luck and
> drive at the GPS speed only to get tickets.
>
> What device should I believe, the GPS or my Cars Speedo ????
>
| |
| utilsea@aol.com 2007-02-26, 4:33 am |
| The most accurate is your GPS if they are using the doppler on SVs to
compute the speed and is about 0.1 m/s.
And even if they use the oldest algo (derivated between two
consecutive point) the accuracy still better than your speedo (about 7
km/h).
Your speedo accuracy is 10% of the speed and relative to the wheels
you use, value of pi (3.14...) and ....
| |
| BlackHole 2007-02-27, 10:33 am |
| If you look at the accuracy specifications for automobile speedometers, you
will find them to typically be -0/+15 percent. If wrong, design has them
reading high.
--
BlackHole
| |
| rthuene@msn.com 2007-02-28, 4:33 am |
| On Thu, 22 Feb 2007 23:39:55 +1100, Razzle <ournet@dcsi.net.au> wrote:
>I have been using my Navman icn720 for a couple of weeks now. I am not
>convinced that it is such a great unit, the map accuracy leads a lot to
>be desired in the rural area that I live, but I can put up with a littl
>of that.
>
>My main concern is that when I am travelling along, my speedo says one
>speed, and the GPS another. Who should I believe?
>
>The GPS is as much as 10kmph slower than my speedo. Which is great if I
>have been always under the limit, but I do not want to push my luck and
>drive at the GPS speed only to get tickets.
>
>What device should I believe, the GPS or my Cars Speedo ????
Have you had the chance to run past on of the police speed trailers?
Around here they leave them on busy streets to have people slow down
when they see them. My GPS unit usually matches the speeds shown on
those so I tend to believe mine.
----== Posted via droptable.com - Unlimited-Unrestricted-Secure Usenet News==----
http://www.droptable.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =----
|
|
|
|
|