Camera van calibration. How can this be acceptable? |
Camera van calibration. How can this be acceptable? |
Sat, 18 Jan 2020 - 21:13
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#1
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New Member Group: Members Posts: 2 Joined: 18 Jan 2020 Member No.: 107,475 |
Hi, new here, and obviously have a dog in this fight unfortunately. I'm interested in the legalities of a device that is only tested and calibrated up to 150 metres, yet is accepted for use for prosecutions of up to 1000 metres. How can the device be decreed as fit for purpose if it is not tested and calibrated for the distances it is required to operate over? Thanks in advance, and sorry if this is a regularly covered topic.
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Sat, 18 Jan 2020 - 21:13
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Sat, 18 Jan 2020 - 21:35
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#2
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Member Group: Members Posts: 601 Joined: 7 May 2019 Member No.: 103,734 |
First thing to say is that the device is a speedmeter that also reports distance. The distance reported has nothing to do with the calculation of the speed.
The 3 sample distances of 25,50 and 75m, the most common device uses those in the calibration, show the linearity of the device. If the device reads those within limits then the device is linear and extrapolation up to the maximum range is used. This is a standard method of calibration of devices. The device is also tested at a minimum of 5 speeds between 20mph and 80mph. If they are within limits then the device is declared linear up to its maximum speed reading. Again, the standard interpolation in the calibration is reasonable. Nothing new in that and the practice is operated by accredited la oratorios and will be accepted by the national authorities accrediting those calibration laboratories. In short your concerns will be no defence but you might dupe a bench of unwary magistrates with them. |
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Sun, 19 Jan 2020 - 09:11
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#3
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New Member Group: Members Posts: 2 Joined: 18 Jan 2020 Member No.: 107,475 |
First thing to say is that the device is a speedmeter that also reports distance. The distance reported has nothing to do with the calculation of the speed. The 3 sample distances of 25,50 and 75m, the most common device uses those in the calibration, show the linearity of the device. If the device reads those within limits then the device is linear and extrapolation up to the maximum range is used. This is a standard method of calibration of devices. The device is also tested at a minimum of 5 speeds between 20mph and 80mph. If they are within limits then the device is declared linear up to its maximum speed reading. Again, the standard interpolation in the calibration is reasonable. Nothing new in that and the practice is operated by accredited la oratorios and will be accepted by the national authorities accrediting those calibration laboratories. In short your concerns will be no defence but you might dupe a bench of unwary magistrates with them. Thanks, didn't expect such a detailed reply. I would imagine that defence has already been tested by many with no reported instances of success, so I certainly don't expect to re-write history. I've already accepted my fate, however, not having much experience with these situations, it seemed a reasonable question to ask. The distance I was measured at was just over 640 metres, I saw the van the instant it was in sight and backed off, pointless as it turns out. Thanks for the response. |
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