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By pilotbarry
#564467
I record all my flights on my Garmin. On playback this gives me date, time, position, height and speed. It is stored in a binary format (not simple text). Would this be admissible in court if the situation ever descended that low?
Has anyone ever had experience of this? I hasten to add that I do NOT low fly, no fast runs and breaks! Honest!!



Please change thread title if you wish.
You could have posted directly as you are registered. :D
Last edited by pilotbarry on Sat Feb 16, 2008 8:31 am, edited 1 time in total.
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By Dave Phillips
#564505
Don't go to court, get the operator to kick him off the airfield. That said, since GPS plots are used by the AAIB, I would presume that they would be admissible.
By Guest
#564598
A record produced by a GPS would in principle be admissible, subject to proof of the functionality of the system when the record was made but, as noted above, surely the best course would be to encourage the airfield owner to ask the anti social pilot to leave.
By Guest
#568160
Now I'm confused... has this thread been edited into incomprehensibility.

Starts with someone wondering if their own GPS could be used against them and ends with someone else getting kicked off an airfield?
By Guest
#571214
Yes it was edited - it initially involved a complaint about someone flying in an anti social manner.
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By yawningdog
#572162
A record produced by a GPS would in principle be admissible, subject to proof of the functionality of the system when the record was made


I think its actually possible to create a false log by connecting a GPC to MS flight simulator via software called GPSout. I have often used an external GPS with the sim to practice using the unit.
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By Gertie
#572179
It's possible to fake any kind of evidence, there's nothing special here about GPS traces.

But I don't recommend it. Judges can get seriously upset if they catch you presenting them with fake evidence.
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By dublinpilot
PFMS Team
#573425
GPS altitudes are not particularly reliable. They were designed for horizontal navigation rather than vertical. Poor positioning of the antenna can seriously affect GPS altitudes.

Different GPS systems have different ways of correcting for the less than perfect spherical shape of the earth, and this can affect the results too.

If a few hundred feet made any difference to the outcome, then I suspect that counsel would rip the evidence to shreds very quickly.

dp
By Guest
#574833
[quote='dublinpilot']GPS altitudes are not particularly reliable. They were designed for horizontal navigation rather than vertical. Poor positioning of the antenna can seriously affect GPS altitudes.

Different GPS systems have different ways of correcting for the less than perfect spherical shape of the earth, and this can affect the results too.

If a few hundred feet made any difference to the outcome, then I suspect that counsel would rip the evidence to shreds very quickly.

dp[/quote]

I'd have to agree with this. My PDA GPS often reports altitudes that are 1-200ft different from my altimeter although it is extremely precise on lateral positioning. It does seem to get more altitude accurate further away from the ground but this would make it more questionable in relation to low-flying infringements
By Guest
#575950
[quote='Anonymous'][My PDA GPS often reports altitudes that are 1-200ft different from my altimeter [/quote]

This would be expected behaviour, even if the GPS were 100% accurate in reporting height, because GPSs and altimeters measure different things.

Altitude on the altimeter is an air pressure measurement which, for practical purposes, is reported to the pilot as feet or metres. This is obvious when you think about re-setting the altimeter for almost every flight, pressure having changed. Pressure does not increase uniformly with height, so if you could measure being exactly 2,000 ft above sea level with a long tape measure, your altimeter might report a figure which differs noticeably.

The GPS attempts to measure actual height above a notional sea level datum.

Airspace altitude boundaries are expressed in terms of pressure altitude, not actual height.

Thus to derive the pressure altitude from a GPS trace, one would need to know the actual sea-level pressure and the pressure gradient for the particular airmass. This would be somewhat difficult!

However, if your GPS says that you are 1,000 ft vertically inside controlled airspace, that's probably pretty good evidence that you are 500 ft or more inside. If it says that you are 100ft inside, it would be very difficult to use the trace to prove that you did infringe.

There's a recently concluded discussion among glider pilots (see rec.aviation.soaring via Google Groups) about whether GPS traces alone could be used to claim badges and records. Currently the technology we use is a secure logger (to record the GPS data) which also contains a pressure altimeter, and it is this pressure altimeter data which is used to validate height gain claims and to reject claims which infringe airspace.
By Granny
#576002
[quote]Altitude on the altimeter is an air pressure measurement which, for practical purposes, is reported to the pilot as feet or metres. This is obvious when you think about re-setting the altimeter for almost every flight, pressure having changed. Pressure does not increase uniformly with height, so if you could measure being exactly 2,000 ft above sea level with a long tape measure, your altimeter might report a figure which differs noticeably.
[/quote]

Gosh, fancy that, well I never, what will they think of next?

I have some ovoid shelled objects here which I would like to suck - anyone able to give me a lesson?

Gran xxx