Actually, it would be fairly straight forward to calibrate the Raymarines:
1. Turn a few handheld GPSs into "transfer standards" by comparing their readings (on land) to radar guns which have been shown to be accurate and whose readings are acceptable in court.
2. Put those GPSs aboard boats and make repetitive test runs past the Raymarines at a range of speeds, while documenting both the GPS readings and the Raymarine readings. (I'd do this using multiple GPS-carrying boats travelling in multiple directions concurrrently.)
3. If the GPS readings agree with the Raymarine readings, you've calibrated the Raymarines and the data they produce should be acceptable in court.
Silver Duck
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