Say Hypothetically, You Get Into an Accident... (You Decide)

[SawMaster]

Your camera is a double edged sword in every way, not just via GPS, since it shows how you were driving too. Use it to remind yourself to drive carefully Average speed can be determined from video; time vs distance is the most accurate measurement of speed as that is what defines it It must be done with care to ensure accuracy but it can be done in most instances. I watch as many crash vids as anyone and much more than most, partly for 'entertainment' and partly as a learning tool. In learning what situations lead to crashes you can better spot and avoid them. Posting your own vids should wait till a crash case is totally settled unless access to the vid is restricted and assigned to only those who need it for legal purposes. Ask and follow your attorney's advice in all legal matters Nobody is a perfect driver including you and me, but it's a goal to strive for and dashcams can help us get closer to that goal even after a crash when you use the vids correctly

Phil

 

[DT MI]

If speed becomes an issue it can easily be determined from the content of the video - with or without GPS.

https://dashcamtalk.com/forum/threads/dome-dab202.17083/#post-222840

...
I doubt it would stand up in Court. In Court in the UK at least, to allege speeding you have to be able to prove an exact speed not an approximate....

Determining the time a vehicle took to travel a known given distance is not an approximation, it's an absolute.

 

[Deleted member 46308]

Ask and follow your attorney's advice in all legal matters

Phil

That is the best advice.

 

[c4rc4m]

Determining the time a vehicle took to travel a known given distance is not an approximation, it's an absolute.

Distance over time = an accurate speed measurement but only if the exact distance travelled can be determined precisely. There are many potential error factors in determining exact distance from a moving camera whilst trying to use roadside objects as reference points.

I understand that's why for reference in the UK (and presumably EU), with fixed camera sites to prevent challenges to calibration they used short dashed lines at known intervals on the road, because they provide a reference to show at a timed interval photograph how far the vehicle has travelled (I believe they use short lines to prevent errors from measuring from different parts of the vehicle). The camera position is fixed and does not move relative to the lines which are also fixed making any parallax or other errors easy to calculate. I believe average speed cameras also use a line drawn in the centre of the lane with both camera and line being fixed relative to each other.

I believe anything from a dashcam video is going to be an approximation of speed due to the inability to prove beyond reasonable doubt that the distance between the reference points and thus speed is accurately measured, and in the UK at least, I'm pretty sure that won't stand up for a speed conviction. In the UK, from memory, you are not charged with "speeding". You are charged with travelling at excess speed, namely X mph in a Y mph zone, where X has to be proven accurate beyond reasonable doubt. I believe merely observing you were exceeding the limit without proving the exact speed is not enough for an excess speed conviction. It may give rise to other charges though as I mentioned above.

I also agree the above is my opinion / understanding and always consult an attorney in your jurisdiction for specific legal advice.

 

[DT MI]

...There are many potential error factors in determining exact distance from a moving camera whilst trying to use roadside objects as reference points.

...The camera position is fixed and does not move relative to the lines which are also fixed making any parallax or other errors easy to calculate....
....

Did you look at the reference I provided in my previous post? In that instance the camera position is constant relative to the vehicle and the distances being measured are known and determined by a fixed reference point on the vehicle thus not affected by parallax. I would suspect that would be valid and admissible in any court unless you had totally incompetent legal representation.

That's my opinion and I'm sticking to it.

 

[Dashmellow]

Distance over time = an accurate speed measurement but only if the exact distance travelled can be determined precisely. There are many potential error factors in determining exact distance from a moving camera whilst trying to use roadside objects as reference points.

Aside from the information provided by @DT MI, most USA highways (and elsewhere) have an extensive system of Highway Location Markers and Mile Markers (modern equivalent of the milestone) making precise distance/time measurements quite accurate and easy.

https://en.wikipedia.org/wiki/Highway_location_marker


New York State highway reference marker


In the UK the system is called the Driver location sign and is placed every 500 meters.

https://en.wikipedia.org/wiki/Driver_location_sign

 

[raqball]

I worked accidents for years and generally speed calculations are going to be an estimate. Speed can be calculated via skid marks from braking, GPS coordinates, roads markers and identifiable terrain. Sometimes a combination of these can be used.

Even with GPS markers and / or speed displayed on a dash cam, speed will still be estimated as GPS has acceptable drift and is not 100% accurate.

Sometimes the speed can be narrowed down to within a few MPH range and sometimes the + / - will be greater than 10 mph. Every incident is different and every jurisdiction has different tools to measure. For Law Enforcement, they'll generally only do this in the case of serious injury or death accidents. For insurance adjusters that's going to depend on the insurance company and the amount of money they stand to lose.

My .02

 

[Dashmellow]

FWIW, I've used highway mile markers to check the accuracy of my speedometer and odometer by timing how long it takes me to go from one mile marker to the next at 60 mph. The odometer did change slightly when I put larger tires on my truck.

 

[kamkar]

Danish highways and larger roads also have distance markers every 100 - 50 or 25 M, it is those 2-3 foot tall white markers on the side of the road.
As i recall only the marker every 100 M will have numbers on them, additional ones will be blanks and just have the refelctor and maybe the identifying number ( side roads and so on will prompt extra markers )
https://www.google.dk/maps/@56.4742...rc3ZFLv_AEJ2Z5qZn5yg!2e0!7i13312!8i6656?hl=da
And here alongside a motorway.
https://www.google.dk/maps/@56.4842...PVU3_qdYjURuEKdjq43A!2e0!7i13312!8i6656?hl=da

They also have numbers on them.

you can see examples of old Danish milestones here
https://da.wikipedia.org/wiki/Milepæl

Our current poles wotk this way.

On top are the KM number to the largest town in the municipality, under that is a line and below it another single digit number indicating 100 M so in the pic its 23 Km and 200 M
The marker also have a unique identifying number you can use if calling for help ( 911 or 112 as it is here )
There is also a little arrow, this use to indicate the direction to the nearest roadside emergency phone, but they are all gone now thanks to cell phones.

Also the top and reflector are slanted, indicating on which side you must pass the pole, just like larger signs that may be on the road at road works and so on.
Furthermore the R hand side reflectors will be yellow and the L hand side ones will have a white reflector as you can see in the streetview links above.

So when i have been visiting my dear old mother on the way home i pass this marker, indicating there are 32.7 KM to Randers where i live, and if you go along the road in street view the next marker will read 32.6 KM
https://www.google.dk/maps/@56.2964...WvQC-JLfk8qz8REXtKqA!2e0!7i13312!8i6656?hl=da

Its rarely hard, you just got to remember what you was told all those years ago getting a license.

Edit: you cant expect these to be the exact distance apart, so for a accurate speed measurement you will have to go measure the exact distance between the 2 poles or features in the footage you use for speed measurement.
BUT ! then you will have a 100% true speed measurement of the camera car.

 

[Dashmellow]

Here's a simple chart that demonstrates how fast you were driving based on the time it takes to drive from one highway mile marker to the next.

speed = distance / time

Seconds - MPH
---------------
36 - 100.0
37 - 97.3
38 - 94.7
39 - 92.3
40 - 90.0
41 - 87.8
42 - 85.7
43 - 83.7
44 - 81.8
45 - 80.0
46 - 78.3
47 - 76.6
48 - 75.0
49 - 73.5
50 - 72.0
51 - 70.6
52 - 69.2
53 - 67.9
54 - 66.7
55 - 65.5
56 - 64.3
57 - 63.2
58 - 62.1
59 - 61.0
60 - 60.0
61 - 59.0
62 - 58.1
63 - 57.1
64 - 56.3
65 - 55.4
66 - 54.5
67 - 53.7
68 - 52.9
69 - 52.2
70 - 51.4
71 - 50.7
72 - 50.0
73 - 49.3
74 - 48.6
75 - 48.0
76 - 47.4
77 - 46.8
78 - 46.2
79 - 45.6
80 - 45.0
81 - 44.4
82 - 43.9
83 - 43.4
84 - 42.9
85 - 42.4
86 - 41.9
87 - 41.4
88 - 40.9
89 - 40.4
90 - 40.0

 

[Rajagra]

Determining the time a vehicle took to travel a known given distance is not an approximation, it's an absolute.

No, it's a measurement, and it's prone to error. You may for example set a dash cam to record at 30 frames per second, but it may actually record at 29, or 25, due either an inaccurate clock signal or software bugs. Playing back a 25fps recording at 30fps would make it seem you were going 20% faster than you really were.

The biggest problem IMO is that a GPS speed stamp that is much higher than the limit tips them off that it is worth investigating your speed further.
Video might also be shown to a jury, I don't know if the speed stamp could be declared inadmissible and edited out.

Sent from my SM-G903F using Tapatalk

 

[Nigel]

No, it's a measurement, and it's prone to error. You may for example set a dash cam to record at 30 frames per second, but it may actually record at 29, or 25, due either an inaccurate clock signal or software bugs. Playing back a 25fps recording at 30fps would make it seem you were going 20% faster than you really were.

It should really be 29.970 fps to match the standard, and my Gitup F1 claims to be that, however my Mini 0906 claims to be 30.000 fps and my B1W claims to be variable with an average of 30.000 fps but dropping to a minimum of 25.052 fps, although I think that when it is less than 30.000 fps it actually duplicates frames so that 30.000 are always written even though they are recorded at 25.052 fps, or any number in-between 25.052 and 30.000 fps.

This does leave the possibility of significant error if you calculate using 30.000 fps and it is really 25.052 fps, and even if it really is recording at 30.000, you should actually check that it does before using it as evidence because computer clock frequencies are not guaranteed to be 100.00000000% accurate, they don't have atomic clocks inside.

 

[c4rc4m]

Did you look at the reference I provided in my previous post? In that instance the camera position is constant relative to the vehicle and the distances being measured are known and determined by a fixed reference point on the vehicle thus not affected by parallax. I would suspect that would be valid and admissible in any court unless you had totally incompetent legal representation.

That's my opinion and I'm sticking to it.

You're entitled to your opinion but you're overlooking several factors that affect accurate measurement. Some possible I can think of include:

1. Parallax errors - whenever a camera looks at an object at an angle you can get parallax errors that throw calculations out: https://en.wikipedia.org/wiki/Parallax

2. The lens is not rectilinear and thus unless the reference objects are in the exact same point on the lens each time (impossible to know or prove as you're talking 100th of a millimetre in such as small lens), then the lens may bend the position slightly differently each time and thus affect the reference

3. The camera is moving and so it's angle to objects at the side of the road is constantly changing. Note here with fixed speed cameras, both the camera and markings on the road are precisely fixed and neither moves.

4. The reference objects need to be the exact same distance from the side of the road otherwise again it could affect parallax

5. The car needs to travel exactly down the same part of the road the same distance from the kerb for the entire distance between the reference points because otherwise if it moves in or out, it is travelling a distance different to that measured as the crow flies between the markers

6. By the same token, if the car deviates in or out from the kerb or if the road curves that can also affect the viewed angle between the vehicle and reference points

7. I'm sure there are other factors as well

I cannot comment on US law, but as I said above, I'm pretty sure in UK law, the charge is travelling at excess speed not "speeding" and the exact known speed has to be quoted to charge with the offence and proven to prove the offence, and that an estimated speed is not sufficient.

Video might also be shown to a jury, I don't know if the speed stamp could be declared inadmissible and edited out.

I believe I read somewhere of a prosecution after the police tested the accuracy of the GPS system in the car against a known calibrated police radar. Hence why I believe GPS speed recording increases not only the chance of a prosecution if the police are involved, but also the chance of losing a civil case as what isn't detectable by eye in a video becomes visible if it's stamped over the footage. I stand to be proven wrong though.

 

[kamkar]

I always drive according to GPS speed in the app i have running on my phone while driving, and i always put my speed on the max when i go past a cop with a speed gun, and so far no fines.
My GPS speed also match good in comparison with the feel guilty radar speed gun signs you often see entering small towns on a larger road.

Seem like google cars are in a hurry in this 50 km/h town zone.
https://www.google.dk/maps/@56.2390...n5ks_1kFB36GoZoPh97Q!2e0!7i13312!8i6656?hl=da

 

[Captain]

So, bottom line, should you use GPS. Or not?

 

[raqball]

So, bottom line, should you use GPS. Or not?

If you speed and drive recklessly then no. If you drive the speed limit and follow the law then maybe. It's really user preference. Another driver may claim you were speeding and the GPS speed data can cast enough doubt on that claim to make it irrelevant. If you were speeding and you turn the footage over to the police or insurance then that can hurt your case, even if the other person was in the wrong.

 

[Rajagra]

So, bottom line, should you use GPS. Or not?

Both.
I have 3 front - facing cameras at the moment, centre and left /right sides of the windscreen. Only the middle one has GPS. If I want it. It has a history of faults though, so it may not have footage for police to inspect. Cough.

Sent from my SM-G903F using Tapatalk

 

[c4rc4m]

So, bottom line, should you use GPS. Or not?

The simple answer is it's personal preference.

Some will say GPS can help prove your innocence if wrongly accused of speeding or if in accident. Others will point out that it can possibly render accident footage useless if you exceed the speed limit even momentarily before an accident.

So it's as it was said above, it's a double edged sword. Personally for me, I see more utility in not having GPS recording than I do in having it. Without it all my footage is usable unless the speed at the time is so fast as to be very obviously in excess of the limit. With it, any footage showing even a few mph over is enough to apportion blame potentially onto me and thus render such footage unusable. As for which to have, you decide...

 

[Captain]

If GPS can be used against you, why would you want to use it?

 

[Nigel]

If GPS can be used against you, why would you want to use it?

If it can be used against you then it can also be used for you