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Originally Posted by Silver Duck
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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It would have to be a range of speed
and ranges as the radars have to determine distance travelled from at least 2 measurements of distance (and then time). To determine distance travelled it'll need to calculate the geometry and that gives you 2* main sources of error, the range error and the angle error. I don't know what Raymarine units the MP has but quickie look at the Raymarine site listed these as 70' or 1.5% of the range setting and 1 degree, respectively, for these. You could calbrate them with GPS but the next question asked would be how long this calibration is good for. Can you go for a year between cals ? A week ? A day ? The best bet would be to have Raymarine specify the accuracy and cal period and live with that. For all I know the units the MP have may be good enough.
*Of course this assumes the MP boat doesn't move in any way. Which of course it will for any "long" observation time. So the MP's would then have to have a GPS and compass reading fed into the calculations. Certainly to prove these factors weren't a factor, they'll need to record them to show they didn't change appreciably during the observation time.