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Timing Accuracy Using GPS Flash Timing
JOA 2024, Vol. 14, No. 3, Page 7 Author(s): Michael CamilleriAbstract: The timing accuracy of short exposure video recordings that have been time stamped using GPS 1 PPS flashes has been measured. Under ideal controlled conditions using an analogue video camera with GPS timestamps as a reference, a timing accuracy of less than 4% (95% CI) of the exposure duration was achieved for exposures ranging from 40 to 1,280 ms, with a maximum error of ±3 ms (95% CI). Under typical real conditions the accuracy was at worst 6% (95% CI) of the exposure time. For typical exposures of 40 to 320 ms the maximum error was ±5 ms (95% CI). When using a digital camera, additional sources of error may occur from PC clock drift and from target drift with a rolling shutter camera. These can be corrected or minimised by measuring the time delays before and after the event and interpolating. Best practice guidelines are provided to help achieve the best accuracy possible. When done properly this method of GPS flash timing is accurate enough for most asteroid occultations and is well suited for large scale campaigns or new observers with ist low cost and versatility.