Green zone fines

[testlab]

Having had a bit to do with aerial surveying in the 90's and early 2000's it is easy to fix a position from the air even if known landmarks are unavailable - back then we used a combination of radar bearings, GPS, WAAS and intertial navigation.

As to the legalities of using GPS for enforcement... it comes down to measurement errors and this is something I know a lot about. If the error of measurement in a position is less that the distance the object is from a boundary then it can be considered in or out of a particular area. So it would likely be admissable in court if the uncertainty of measurement has been determined and quantified.

Defining maritime boundaries is not a completely precise science but it is nonetheless highly accurate. GPS used in aircraft are vastly different to those used by recreational (and even pro) boaties. GPS precision approaches demand very small errors in both horizontal and vertical planes. There is also WAAS (wide area augmentation system) which brings the GPS error down to insignificant amounts. This is how GPS surveying on farms, properties and building sites can be highly accurate.

Basic aerial survey techniques would easily be able to measure a boat position to an accurarcy of 100m from two kilometers away and if they had the right gear could reduce that error to meters or even cms. There are lots of techniques including measuring direct path distance and bearing using radar.

So long as the errors are known and taken into account when deciding how to determine a position (and the precision doesn't have to be all that great) they should be able to confidently say you were "there"... and if the +/- of that position is less than the distance to the boundary, plus the error in determining where the boundary actually is, its a good positional fix.

Its way beyond the ability of the average GPS user to get this kind of precision and just like the way radar speed infringements were ruled inadmissable for a time due to the police not scientifically determining the measurement uncertainty - they only need to get bitten by the courts once to make the necessary changes. So precedent can only be relied on for so long.

So keeping a reasonable distance from the boundaries, unless you can say for certain where they are, is good insurance against getting pinged.