|
|
|
Suppose you were driving along at the posted speed limit. Speeders are passing
you on the left almost continually. Suddenly, you see the red and blue disco
lights in your rear-view-mirror. You pull over, and the cop says he clocked you
doing 10 MPH over the limit. You try explaining that you were driving the speed
limit and he must have clocked one of the other cars that was passing you, but
he'll hear none of it; you get the ticket.
You go home and dump the track log from the GPS unit you just happened to have
in your car. The GPS track log consists of a series of data records, saved once
per second, each containing a timestamp, a position, and a speed (computed from
the change of position since the last position report). Your GPS log confirms
that at no time did you exceed the posted limit along your route.
If you decide to go to court to fight this unfair ticket, will the judge admit
your GPS track log as evidence? You would, of course, plot the positions and
speeds on a map of the area for the convenience of the judge.
You would, of course, swear under oath that you had not altered the data in the
track log in any way so as to make your speeds appear lower.
Would this be worth trying?
--
Why do you keep posting that comment from that idiot Pride of America?
- "Laura Bush murdered her boy friend," Wed, 03 Mar 2004 01:08:03 -0700
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| |
Scott in Aztln wrote:
Suppose you were driving along at the posted speed limit. Speeders are
passing you on the left almost continually. Suddenly, you see the red and
blue disco lights in your rear-view-mirror. You pull over, and the cop
says he clocked you doing 10 MPH over the limit. You try explaining that
you were driving the speed limit and he must have clocked one of the
other cars that was passing you, but he'll hear none of it; you get the
ticket.
You go home and dump the track log from the GPS unit you just happened to
have in your car. The GPS track log consists of a series of data records,
saved once per second, each containing a timestamp, a position, and a
speed (computed from the change of position since the last position
report). Your GPS log confirms that at no time did you exceed the posted
limit along your route.
If you decide to go to court to fight this unfair ticket, will the judge
admit your GPS track log as evidence? You would, of course, plot the
positions and speeds on a map of the area for the convenience of the
judge.
You would, of course, swear under oath that you had not altered the data
in the track log in any way so as to make your speeds appear lower.
Would this be worth trying?
By all means, go for it.
The next best thing is to have video evidence.
In today's modern high tech society, I would think the courts would have to
accept such evidence.
The other side could though, claim the evidence was fabricated by using a
simple item like notepad.
Question is, why did the officer select you out of others who were obviously
in violation?
Perhaps he felt your car matched the description of a wanted vehicle.
Or your license plate closely resembled a wanted vehicle.
If you are not guilty, by all means, challenge it.
Make them go to the expense of seating a jury.
Are you a member of an ethnic minority? Use racial profiling as a possible
method to beat it.
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It's worth a shot. Be sure to bring in the actual GPS with the track log on
it. You can potentially modify the PC data, but not the data on the GPS
itself.
Suppose you were driving along at the posted speed limit. Speeders are
passing
you on the left almost continually. Suddenly, you see the red and blue
disco
lights in your rear-view-mirror. You pull over, and the cop says he
clocked you
doing 10 MPH over the limit. You try explaining that you were driving the
speed
limit and he must have clocked one of the other cars that was passing you,
but
he'll hear none of it; you get the ticket.
You go home and dump the track log from the GPS unit you just happened to
have
in your car. The GPS track log consists of a series of data records, saved
once
per second, each containing a timestamp, a position, and a speed (computed
from
the change of position since the last position report). Your GPS log
confirms
that at no time did you exceed the posted limit along your route.
If you decide to go to court to fight this unfair ticket, will the judge
admit
your GPS track log as evidence? You would, of course, plot the positions
and
speeds on a map of the area for the convenience of the judge.
You would, of course, swear under oath that you had not altered the data
in the
track log in any way so as to make your speeds appear lower.
Would this be worth trying?
--
Why do you keep posting that comment from that idiot Pride of America?
- "Laura Bush murdered her boy friend," Wed, 03 Mar 2004 01:08:03 -0700
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| |
In article <g3lb50pjbo6rprh7jqtphha0mn8o3vmvoa@4ax.com>,
Scott in Aztln <newsgroup> wrote:
You go home and dump the track log from the GPS unit you just happened to have
in your car. The GPS track log consists of a series of data records, saved once
per second, each containing a timestamp, a position, and a speed (computed from
the change of position since the last position report).
Actually, that's not how GPS computes speed.
Your GPS log confirms
that at no time did you exceed the posted limit along your route.
If you decide to go to court to fight this unfair ticket, will the judge admit
your GPS track log as evidence? You would, of course, plot the positions and
speeds on a map of the area for the convenience of the judge.
I don't know whether he would or not, but it's not very credible
evidence. I could fake a GPS log easy enough. And the defendant
swearing he didn't is about as likely to be believed as the defendant
swearing he didn't speed.
Would this be worth trying?
Sure, what do you have to lose.
--
Matthew T. Russotto mrussotto@speakeasy.net
"Extremism in defense of liberty is no vice, and moderation in pursuit
of justice is no virtue." But extreme restriction of liberty in pursuit of
a modicum of security is a very expensive vice.
|
| |
| |
In article <g3lb50pjbo6rprh7jqtphha0mn8o3vmvoa@4ax.com>,
slothkills@THEyahooOBVIOUS.com says...
Suppose you were driving along at the posted speed limit. Speeders are passing
you on the left almost continually. Suddenly, you see the red and blue disco
lights in your rear-view-mirror. You pull over, and the cop says he clocked
you
doing 10 MPH over the limit. You try explaining that you were driving the
speed
limit and he must have clocked one of the other cars that was passing you, but
he'll hear none of it; you get the ticket.
You go home and dump the track log from the GPS unit you just happened to have
in your car. The GPS track log consists of a series of data records, saved
once
per second, each containing a timestamp, a position, and a speed (computed
from
the change of position since the last position report). Your GPS log confirms
that at no time did you exceed the posted limit along your route.
If you decide to go to court to fight this unfair ticket, will the judge admit
your GPS track log as evidence? You would, of course, plot the positions and
speeds on a map of the area for the convenience of the judge.
You would, of course, swear under oath that you had not altered the data in
the
track log in any way so as to make your speeds appear lower.
Would this be worth trying?
They might accept that GPS is a valid, and accurate, way to measure the speed
of a car. But it couldn't hurt to try.
-------------
Alex
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Najena wrote:
It'd be worth it, but the cop may complain that you're testifying as an
unqualified expert, and the judge may agree.
This is the first I've heard of it; it sounds like a good idea.
I was thinking also that the DOT has done the same thing with Qualcomm
satellite.
Using the reports it generates to show that a trucker lied about where he
was at a given time.
Or showing he was sleeping when the truck was moving.
So the courts should accept the gps device as evidence just the same.
But I would think that being the unit is portable enough to bring into the
court room, you could just plug it into the computer in the court room so
that there was no way any one could object to the authenticity of the
reports.
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On 16 Mar 2004 05:32:23 GMT, Najena <najena@coldmail.com> wrote:
It'd be worth it, but the cop may complain that you're testifying as an
unqualified expert, and the judge may agree.
My response would be that I'm at least as well qualified to use a GPS receiver
as the cop is to use a radar gun. :)
--
Why do you keep posting that comment from that idiot Pride of America?
- "Laura Bush murdered her boy friend," Wed, 03 Mar 2004 01:08:03 -0700
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It'd be worth it, but the cop may complain that you're testifying as an
unqualified expert, and the judge may agree.
This is the first I've heard of it; it sounds like a good idea.
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Scott in Aztln wrote:
On 16 Mar 2004 05:32:23 GMT, Najena <najena@coldmail.com> wrote:
It'd be worth it, but the cop may complain that you're testifying as an
unqualified expert, and the judge may agree.
My response would be that I'm at least as well qualified to use a GPS
receiver as the cop is to use a radar gun. :)
So what you do is, you have a representative of the GPS company come to
court and explain how it works. Then he is seen as the expert witness.
"Expert witness" generally means a person who is trained, educated and paid
in that field.
An officer would be an "expert witness" when it comes to radar guns.
You could also argue that the radar gun is an electronic radio device which
is susceptible to it's surroundings and is also subject to failure merely by
the fact that it uses radio waves.
A radar radio signals cares not what it bounces off of to acquire a
"reading".
So how would the officer know for a fact that your vehicle was the only
vehicle the signal bounced off of?
Picture this if you will.
10 cars in two lanes pass by an officer sitting in the median.
He is sitting at a precise 90 degrees to the vehicles.
He clocks YOUR speed as being over the speed limit.
His radar gun has mulfunctioned.
How so?
Because at a precise 90 degrees, the returned indication should read 0 mph.
For the reasoning that the object being tracked has neither moved away nor
towards the signal.
That is why the officer's vehicle must be sitting at an angle, preferably
almost parallel to the roadway.
This is documented on the internet.
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| |
| |
| Suppose you were driving along at the posted speed limit. Speeders are
passing
| you on the left almost continually. Suddenly, you see the red and blue disco
| lights in your rear-view-mirror. You pull over, and the cop says he clocked
you
| doing 10 MPH over the limit. You try explaining that you were driving the
speed
| limit and he must have clocked one of the other cars that was passing you,
but
| he'll hear none of it; you get the ticket.
|| You go home and dump the track log from the GPS unit you just happened to
have
| in your car. The GPS track log consists of a series of data records, saved
once
| per second, each containing a timestamp, a position, and a speed (computed
from
| the change of position since the last position report). Your GPS log confirms
| that at no time did you exceed the posted limit along your route.
|| If you decide to go to court to fight this unfair ticket, will the judge
admit
| your GPS track log as evidence? You would, of course, plot the positions and
| speeds on a map of the area for the convenience of the judge.
|| You would, of course, swear under oath that you had not altered the data in
the
| track log in any way so as to make your speeds appear lower.
|| Would this be worth trying?
|| --
| Why do you keep posting that comment from that idiot Pride of America?
|| - "Laura Bush murdered her boy friend," Wed, 03 Mar 2004 01:08:03 -0700
My guess is that the court would want the GPS data "certified" in some way to
accept it. But, hey, I would give it a shot!
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It'd be worth it, but the cop may complain that you're testifying as an
unqualified expert, and the judge may agree.
This is the first I've heard of it; it sounds like a good idea.
Bring the instruction manual that came with the GPS device and
advertising by the manufacturer for it along with you. A representative
of the manufacturer would be nice, too, but that's probably too
expensive. You called it a "GPS tracker"; that's something different
from a GPS device and a laptop computer. The tracker keeps logs
in itself, not in the computer, and probably doesn't allow editing
the logs.
Some points to emphasize:
The GPS tracker probably lets you log data and maybe erase it, but
it does not let you upload altered data into it. (Other gadgets
are often the same way: blood pressure monitors log data but don't
let you edit it. There's no point to allowing it.) Some GPS
trackers are marketed to parents and employers to check on what
your teens/employees are doing with the car/truck, so they are proud
of this tamper-proof feature and may say so in advertising.
Be sure the track STAYS in the GPS tracker. Don't let it scroll
off the end of its memory by continuing to use it. It's fine having
a nice map of where you went with the speeds shown, but you also
want the data in the tracker where it's allegedly tamper-proof so
a third party could look at it and say it matches your map. Data
in your computer is certainly NOT tamper-proof. It wouldn't hurt
to bring in a computer so you can demonstrate (or let someone else
demonstrate) loading the data from the GPS tracker. Actually, you
probably prefer they use their own computer, but have one handy
just in case.
GPS carries with it its own time stamps - quite accurate ones, down
to fractions of a second. This information is computed along with
your position and hopefully the timestamp is logged also. You
cannot fake a "non-speeding" log by resetting the clock and driving
the same route at a legal speed the next day, because you cannot
"reset the clock".
Gordon L. Burditt
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Richard,
Expert witnesses are hired to testify and are not cheap. I doubt that
anyone would use such a witness for traffic court.
Also, if at time A you are located at X and at time B you are located at
Y then you can calculate the average speed in traveling from X to Y. But,
this is not evidence that you did not exceed the speed limit at some point
between X and Y. The distance traveled between X and Y may not be the
shortest distance between X and Y and the speed may not have remained
constant. The poster claims that his GPS unit logs every second. I'd be
interested in having this confirmed.
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gordonb.agvyd@sneaky.lerctr.org (Gordon Burditt) wrote in news:c381ek$oh2
@library2.airnews.net:
It'd be worth it, but the cop may complain that you're testifying as an
unqualified expert, and the judge may agree.
This is the first I've heard of it; it sounds like a good idea.
Bring the instruction manual that came with the GPS device and
advertising by the manufacturer for it along with you. A representative
of the manufacturer would be nice, too, but that's probably too
expensive. You called it a "GPS tracker"; that's something different
from a GPS device and a laptop computer. The tracker keeps logs
in itself, not in the computer, and probably doesn't allow editing
the logs.
I'm not the OP.
In PA, the manual would do no good. That is hearsay, and PA doesn't have
the learned treatise exception to the hearsay rule.
The judge may make you qualify as an expert before he lets you testify as
to what the logs mean in relation to the case, and unless you have
verfiable knowledge in the field, above that of a layman, you won't
qualify.
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"Richard" <Anonymous@127.000> wrote in
news:c367a3082g@enews4.newsguy.com:
But I would think that being the unit is portable enough to bring into
the court room, you could just plug it into the computer in the court
room so that there was no way any one could object to the authenticity
of the reports.
It's not about the authenticity of the reports; it's about whether the
witness is competent to testify about what the report means.
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On Wed, 17 Mar 2004 01:51:51 GMT, "David Martel" <marte005@earthlink.net> wrote:
Also, if at time A you are located at X and at time B you are located at
Y then you can calculate the average speed in traveling from X to Y. But,
this is not evidence that you did not exceed the speed limit at some point
between X and Y.
Position samples in a GPS log are taken at 1-second intervals; do you think you
can exceed the speed limit in such a way that a) the average speed over the
second is still at or below the posted limt, and b) the cop could still obtain a
radar speed reading that would show your peak speed? ;)
The poster claims that his GPS unit logs every second. I'd be
interested in having this confirmed.
This is pretty much standard for all of the GPS units I have ever used (which
numbers about half a dozen). It's certainly true for all the units I currently
own.
--
Why do you keep posting that comment from that idiot Pride of America?
- "Laura Bush murdered her boy friend," Wed, 03 Mar 2004 01:08:03 -0700
|
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| |
Scott in Aztln wrote:
It'd be worth it, but the cop may complain that you're testifying as an
unqualified expert, and the judge may agree.
So what you do is, you have a representative of the GPS company come to
court and explain how it works. Then he is seen as the expert witness.
How much is that going to cost you?
"Expert witness" generally means a person who is trained, educated and
paid
in that field.
Right. For a speeding ticket. Why are you so st00pid, Bullis?
An officer would be an "expert witness" when it comes to radar guns.
You could also argue that the radar gun is an electronic radio device
which
is susceptible to it's surroundings and is also subject to failure merely
by
the fact that it uses radio waves.
A radar radio signals cares not what it bounces off of to acquire a
"reading".
So how would the officer know for a fact that your vehicle was the only
vehicle the signal bounced off of?
Oh yeah, that's going to work, St00pid. You just said the officer would be
an expert witness.
Picture this if you will.
10 cars in two lanes pass by an officer sitting in the median.
He is sitting at a precise 90 degrees to the vehicles.
He clocks YOUR speed as being over the speed limit.
His radar gun has mulfunctioned.
How so?
Because at a precise 90 degrees, the returned indication should read 0
mph.
For the reasoning that the object being tracked has neither moved away nor
towards the signal.
That is why the officer's vehicle must be sitting at an angle, preferably
almost parallel to the roadway.
This is documented on the internet.
So is your st00pidity, Bullis. Stop practicing law from your filthy trailer
and get a job.
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Scott,
I looked for the rate of logging on the net. One unit logged every 5
mins. Many of the units claim to measure speed but none that I found
actually mentioned the rate of logging. I did not, in my brief look, find
any unit that logged at once per second. I do think that such a rate would
give a pretty good speed indicator on most roads but I've not done the math.
If you go down a steep hill would the GPS info still correlate well with
speed? Without an expert opinion on this sort of question I wonder if any
court would allow such logs.
Dave M.
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"David Martel" wrote
I did not, in my brief look, find
any unit that logged at once per second.
I.e. with the Garmin 76s you can choose how to log.
- automatic (depending on turns, speed, distance and time)
- time (in intervalls from 1 second to 1 day)
- distance (from 10 meters to 9.99 kilometers)
It can save 10000 track points and you can select if it should
stop logging or overwrite old points if memory is filled.
If you go down a steep hill would the GPS info still
correlate well with speed?
What do you mean with "well"?
Remember school time and ancient phythagoras:
in most cases the difference will by <1%.
There are GPS units (like the 76s) which calculate
vertical speed too (and other things for pilots like actual
and desired gliding ratio to target etc.).
Thomas
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In article <_PY5c.44408$aT1.2073@newsread1.news.pas.earthlink.net>,
David Martel <marte005@earthlink.net> wrote:
Scott,
I looked for the rate of logging on the net. One unit logged every 5
mins. Many of the units claim to measure speed but none that I found
actually mentioned the rate of logging. I did not, in my brief look, find
any unit that logged at once per second.
You didn't look very carefully then. Nearly all handheld GPS units
can log every second.
I do think that such a rate would
give a pretty good speed indicator on most roads but I've not done the math.
You don't need to; the GPS does not measure speed by calculating the
distance between the two most recently logged points.
If you go down a steep hill would the GPS info still correlate well with
speed?
Many GPS units show only 2D velocity (though they calculate 3D
velocity internally). However, it makes no significant difference for
just about anywhere an officer would be running radar.
--
Matthew T. Russotto mrussotto@speakeasy.net
"Extremism in defense of liberty is no vice, and moderation in pursuit
of justice is no virtue." But extreme restriction of liberty in pursuit of
a modicum of security is a very expensive vice.
|
| |
| |
On Wed, 17 Mar 2004 13:58:18 GMT, "David Martel" <marte005@earthlink.net> wrote:
I looked for the rate of logging on the net. One unit logged every 5
mins.
For use in a "moving map" car navigation system, a 5-minute update interval
would be less than useless. This is why my Garmin Street Pilot spits out
position updates approximately once per second.
Many of the units claim to measure speed
Even if they don't, it's a trivial matter of first grade math to determine speed
from a series of timestamped positions. Or am I "not an expert in the field" of
basic multiplication? ;)
--
Why do you keep posting that comment from that idiot Pride of America?
- "Laura Bush murdered her boy friend," Wed, 03 Mar 2004 01:08:03 -0700
|
| |
| |
In article <c37lht0dqa@enews3.newsguy.com>, Anonymous@127.000 says...
So what you do is, you have a representative of the GPS company come to
court and explain how it works. Then he is seen as the expert witness.
I'm usre they won't do this for free.
"Expert witness" generally means a person who is trained, educated and paid
in that field.
An officer would be an "expert witness" when it comes to radar guns.
An office is an expert when it comes to the operation of radar guns.
Just like you can be an expert in the use of your TV remote and not need
to know how the device works.
You could also argue that the radar gun is an electronic radio device which
is susceptible to it's surroundings and is also subject to failure merely by
the fact that it uses radio waves.
A radar radio signals cares not what it bounces off of to acquire a
"reading".
So how would the officer know for a fact that your vehicle was the only
vehicle the signal bounced off of?
This is a valid point. Radar offers no target identification and it takes
a very carefull operator to make sure he takes his best guess as to what
object is causing the reading on the gun.
Picture this if you will.
10 cars in two lanes pass by an officer sitting in the median.
He is sitting at a precise 90 degrees to the vehicles.
He clocks YOUR speed as being over the speed limit.
His radar gun has mulfunctioned.
How so?
Because at a precise 90 degrees, the returned indication should read 0 mph.
For the reasoning that the object being tracked has neither moved away nor
towards the signal.
That is why the officer's vehicle must be sitting at an angle, preferably
almost parallel to the roadway.
This is documented on the internet.
Commonly referred to as cosine error. In stationary mode, this works in
the cars favor because it gives a lower reading. In moving mode this can
work against the car being clocked because if it reads the cop cars speed
as lower than actual, it will inflate the target vehicles speed by the same
amount.
-----------------
Alex
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| |
| |
In article <c37lht0dqa@enews3.newsguy.com>, Anonymous@127.000 says...
I'm usre they won't do this for free.
An office is an expert when it comes to the operation of radar guns.
Just like you can be an expert in the use of your TV remote and not need
to know how the device works.
This is a valid point. Radar offers no target identification and it takes
a very carefull operator to make sure he takes his best guess as to what
object is causing the reading on the gun.
Maybe in the past. This is a high-end unit, though. Bullis wouldn't know.
http://www.stalkerradar.com/law_dsr.shtml
Picture this if you will.
10 cars in two lanes pass by an officer sitting in the median.
He is sitting at a precise 90 degrees to the vehicles.
He clocks YOUR speed as being over the speed limit.
His radar gun has mulfunctioned.
How so?
Because at a precise 90 degrees, the returned indication should read 0
mph.
For the reasoning that the object being tracked has neither moved away
nor
towards the signal.
That is why the officer's vehicle must be sitting at an angle, preferably
almost parallel to the roadway.
This is documented on the internet.
Commonly referred to as cosine error. In stationary mode, this works in
the cars favor because it gives a lower reading. In moving mode this can
work against the car being clocked because if it reads the cop cars speed
as lower than actual, it will inflate the target vehicles speed by the
same
amount.
-----------------
Alex
|
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| |
I looked for the rate of logging on the net. One unit logged every 5
mins. Many of the units claim to measure speed but none that I found
actually mentioned the rate of logging.
GPS units are certainly capable of producing one reading per second.
Whether it's logged every time is another matter. This may be a
settable parameter. For a unit designed to keep track of where the
vehicle went, logging may not be done as often to make the log last
longer, as logging memory is likely limited. If you're concerned
about the vehicle showing up in a city where it shouldn't be, once
every 5 minutes is plenty. (For a 10,000 reading memory (could
probably fit in 128Kbytes), taking a reading every 5 minutes gives
about 34.7 days of logs (practical for a fleet of trucks), but
taking a reading every second gives about 2.7 hours of logs, not
enough to cover all trips). If you're concerned about brief instances
of speeding, once every 5 minutes is useless.
Radar units also read an average speed over some period of time.
What is that time? I don't think it's as short as 1 second. 5
seconds, maybe? Anyone know how long it takes radar to "lock" onto
a vehicle and give a valid reading? What time period is used to
average a reading once you've got a lock?
I did not, in my brief look, find
any unit that logged at once per second. I do think that such a rate would
give a pretty good speed indicator on most roads but I've not done the math.
If you go down a steep hill would the GPS info still correlate well with
speed? Without an expert opinion on this sort of question I wonder if any
court would allow such logs.
You can compute the speed from two position readings and the time
difference between them. If you are in an area with a lot of really
steep hills (say, 45 degree slope), the 3D distance, not the 2D
distance is an issue. (For example, 84.8 MPH up or down a 45 degree
slope reads as a 60MPH 2D distance, assuming no GPS measurement
error. But how many freeways have roads that steep? I don't think
the highway department is willing to build roads like that. A 20
degree slope gives about a 6% error in the speed, so 63.8 MPH would
read as 60 MPH. That's not a large error. How accurate is traffic
radar in the MPH reading?). GPS produces an altitude number also,
which can be used to compute a 3D speed. Does it log it? Maybe,
maybe not. It depends on the unit. It might not even display it.
Altitude on a unit intended for use on boats is pretty useless. If
you are a rental car company and your main concern is the car driving
into Mexico, you don't care. If you are concerned about your teen
"testing" the power in your engine by briefly flooring it when he
gets a chance, maybe you do.
60 MPH = 88 feet per second. If logs are being done every second,
you don't get to do much speeding in one second while still keeping
the average under the speed limit. On the other hand, you can go
5 miles in 5 minutes even at the speed limit, plenty of time for a
drag race.
Beware that GPS can lose contact with the satellites, and from the
point of view of the log, you stopped moving. Logs may or may not
log indications of quality of the reading (number of satellites
used, etc.) Then when it resyncs, you seem to have moved really,
really fast. If the court sees that, you might get a really, really
big fine.
Real-life example: I almost always lose the signal from most
(usually ALL at some point) of the satellites when I drive through
an "urban canyon" like Main Street in downtown Dallas. I can't see
much sky except straight up, there are too many tall buildings in
the way. From the logs, it might appear that I spent 90 seconds
at a dead stop followed by a short spurt at 900 MPH, when I actually
averaged more like 25 MPH while moving and 0 MPH while stopped at
many of the red lights on that street, for an overall average of
10 MPH.
Another issue is the granularity of the position reading. Mine
reads position down to thousandths of minutes. I didn't say it was
that accurate (it's not) - but it doesn't even provide digits for
more accuracy, so it can't be MORE accurate than that. (For latitude,
0.001 minutes = about 6.1 feet. For longitude, where I live (Texas)
or places at about the same latitude, 0.001 minutes longitude =
about 5 feet). If you are calculating the difference between two
positions to compute speed, the difference is going to be some
multiple of that 6.1 feet. If you were going slightly under 60 MPH
(the speed limit) north-south, your speed will compute out to 62.386
MPH (you went 15 * 6.1 feet) or 58.227 MPH (you went 14 * 6.1 feet)
for each second, no reading between those two values is possible.
Were you speeding? No, but your father or boss may look at that
62.386 MPH reading every third second and conclude that you were.
Internally, the GPS may have more accuracy if it comes up with a
speed number (is that a 2D speed or a 3D speed? Might be either.).
Or it may give an average over a longer period of time than one
second. You can average over periods of time longer than one second,
but then the objection will be that you're doing it to cover up the
short instances of speeding.
Incidentally, GPS produces internally a very accurate estimate of
the time as part of its calculations, down to microseconds. Does
the sub-second time get logged? Doubtful. Chances are most GPS
units don't have a good way to signal exactly when the time matched
the data in a $GPRMC record, and transmitting such a record via a
serial or USB port can take a good fraction of a second. This is
sort of like trying to set your clock by USPS mail. You can use
GPS for a time server but generally it requires more wires brought
out than units for logging have.
Gordon L. Burditt
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In article <105hc9e9faarra7@news.supernews.com>, xxx@yyy.zzz says...
You could also argue that the radar gun is an electronic radio device
which
is susceptible to it's surroundings and is also subject to failure merely
by
the fact that it uses radio waves.
A radar radio signals cares not what it bounces off of to acquire a
"reading".
So how would the officer know for a fact that your vehicle was the only
vehicle the signal bounced off of?
Maybe in the past. This is a high-end unit, though. Bullis wouldn't know.
http://www.stalkerradar.com/law_dsr.shtml
It tells you whether a target on which antenna, it has a front and back. It
tells you the speed of the strongest reflected signal and the fastest signal.
But is still does not tell you what it is measuring or the range. So once it
too offers no target identification. It does provide better, and more,
information to the operator so that they can take a better guess.
--------------
Alex
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In article <105fo41nev2agc8@news.supernews.com>, "informant"(xxx@yyy.zzz)
dropped a +5 bundle of words...
How much is that going to cost you?
That's a third mortgage on the double-wide for st00pid.
paid
Right. For a speeding ticket. Why are you so st00pid, Bullis?
No #@($, all you have to do is show up to traffic court and they take
points and money off the ticket.
which
by
Oh yeah, that's going to work, St00pid. You just said the officer would be
an expert witness.
St00pid would argue a speeding ticket into a felony if you gave him the
chance. Good thing nobody will ever give him the chance except for
St00pid himself, of course.
mph.
So is your st00pidity, Bullis. Stop practicing law from your filthy trailer
and get a job.
Does his law library lean to the left like his 'deck'??
--
mhm 31x9
Smeeter #28, 29, or 30
WSD #30
Skep-ti-cult ID# 365-12149-907
Alcatroll Labs Inc. (Division of Incendiary Devices)
StArSHiNe_MoOnbEAm aT HoTMaIL DoT cOM
http://www.geocities.com/tobydog9
"Technology is getting better and that's fine but most of the time,
all you need is a stick of gum, a pocketknife, and a smile."
-- Robert Redford "Spy Game"
"You can run but you'll just die tired and buttered."
-- Ryannosaurus
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In article <c3ae01$eim@library1.airnews.net>,
Gordon Burditt <gordonb.bfdd6@sneaky.lerctr.org> wrote:
Radar units also read an average speed over some period of time.
What is that time? I don't think it's as short as 1 second. 5
seconds, maybe? Anyone know how long it takes radar to "lock" onto
a vehicle and give a valid reading? What time period is used to
average a reading once you've got a lock?
Theoretically, radar units record instantaneous speed using the
doppler effect. In practice, I'm sure this is filtered to some extent
giving effectively an average speed over a fraction of a second.
--
Matthew T. Russotto mrussotto@speakeasy.net
"Extremism in defense of liberty is no vice, and moderation in pursuit
of justice is no virtue." But extreme restriction of liberty in pursuit of
a modicum of security is a very expensive vice.
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Radar units also read an average speed over some period of time.
What is that time? I don't think it's as short as 1 second. 5
seconds, maybe? Anyone know how long it takes radar to "lock" onto
a vehicle and give a valid reading? What time period is used to
average a reading once you've got a lock?
Theoretically, radar units record instantaneous speed using the
doppler effect. In practice, I'm sure this is filtered to some extent
giving effectively an average speed over a fraction of a second.
If they are using the doppler effect, they need to measure the
frequency of the reflected signal. You can't measure frequency
instantaneously. You at least need to count up something like half
a cycle. Given the existence of noise, you need to count up a lot
more than that to measure a small change in frequency, and filter
out the completely irrelevant stuff, like 60Hz power-line hum and
the police officer's own engine noise, to say nothing of commercial
radio and TV transmissions and the police officer's radio. Yes,
these are on very different frequencies so they can be filtered
(although nothing can be filtered completely). I am not sure how
much time this takes for practical accuracy of a real radar unit.
Oh, yes, real radar units need to measure the overall speed of the
car itself, not the speed of, say, the fan belt or the radiator
cooling fan. Having your fan blades exceed the speed limit is not
illegal if the overall car is under the speed limit. There are
some alleged tricks taking advantage of this to make radar units
read LOWER than the real speed. I don't know whether they work
enough to be worth money.
Gordon L. Burditt
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On Thu, 18 Mar 2004 12:16:27 -0600, russotto@grace.speakeasy.net
(Matthew Russotto) wrote:
In article <c3ae01$eim@library1.airnews.net>,
Gordon Burditt <gordonb.bfdd6@sneaky.lerctr.org> wrote:
Theoretically, radar units record instantaneous speed using the
doppler effect. In practice, I'm sure this is filtered to some extent
giving effectively an average speed over a fraction of a second.
Well, you are talking about the theory of how one could work. While I
do not profess to be an expert in the software behind them, the fact
is that the engineer could have designed them to require a few seconds
of constant speed reading, or a mili second. One does not know unless
they crack the code or do some testing.
Also, there is no such thing as instantaneous, although I suspect you
did not mean it literally. Radar waves travel at the speed of light,
which of course means the farther away the object is, the longer it
takes to read the speed. In practice, this is not measurable due to
the speed of the wave in relation to the distance a radar gun is used
at.
So, the real answer would be somewhere in between almost instantaneous
and whatever delay was built in by the engineer. I know that people
who decel fast enough have been able to beat the radar, while still
being ticketed since the speed reduction is so blatantly obvious. Cop
wrote them for visual instead of radar, which is just as good to most
courts.
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russotto@grace.speakeasy.net (Matthew Russotto) writes:
In article <c3ae01$eim@library1.airnews.net>,
Gordon Burditt <gordonb.bfdd6@sneaky.lerctr.org> wrote:
Theoretically, radar units record instantaneous speed using the
doppler effect. In practice, I'm sure this is filtered to some extent
giving effectively an average speed over a fraction of a second.
Theoretically, it can't be instantaneous as it's a frequency
measurement. :-)
--
/"\ Bernd Felsche - Innovative Reckoning, Perth, Western Australia
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X against HTML mail | Copy me into your ~/.signature
/ \ and postings | to help me spread!
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DTJ <dtj@comcast.net> writes:
On Thu, 18 Mar 2004 12:16:27 -0600, russotto@grace.speakeasy.net
(Matthew Russotto) wrote:
In article <c3ae01$eim@library1.airnews.net>,
Gordon Burditt <gordonb.bfdd6@sneaky.lerctr.org> wrote:
Radar units also read an average speed over some period of time.
What is that time? I don't think it's as short as 1 second. 5
seconds, maybe? Anyone know how long it takes radar to "lock" onto
a vehicle and give a valid reading? What time period is used to
average a reading once you've got a lock?
Theoretically, radar units record instantaneous speed using the
doppler effect. In practice, I'm sure this is filtered to some extent
giving effectively an average speed over a fraction of a second.
Well, you are talking about the theory of how one could work. While I
do not profess to be an expert in the software behind them, the fact
is that the engineer could have designed them to require a few seconds
of constant speed reading, or a mili second. One does not know unless
they crack the code or do some testing.
That's now illegal under DMCA.
All reverse engineering is basically illegal.
--
/"\ | | |
