[Woodsy]

You need to understand how police radar works, to understand why it is not useful for speed limit enforcement on Lake Winnipesaukee or any other body of water.

Radar (either Electronic or Laser) in the simplest of terms, works on the principle of shooting an electron beam in a straight line (straight line being very important) against a target and measuring the time it takes to reflect back. The time it takes the electron beam to reflect back is processed with an equation to give the police officer the target vehicle speed in MPH. It’s a pretty simple process when used on roadways against speeding automobiles traveling in fixed lanes relative to the position of the radar emitter. It becomes a lot more difficult when used on the water… let me explain.

You are traveling in your car down the highway, traveling at 65mph (or whatever speed you choose) and you happen across your friendly neighborhood State Trooper sitting on the side of the road with his handy dandy ACME Mark XXIV Radar Emitter. In this situation, as with most situations involving cars and radar, you are traveling along in the road in fixed bearing relative to the radar emitter. Fixed bearing means that your direction of travel relative to the radar emitter is known and cannot be deviated from. Think triangle. I have attached a simple diagram to explain. The direction you are traveling is known, and the distance from the radar unit to the centerline of your path of travel is also known and is extremely short relative to the range at which the radar emitter can “see” your car (usually ¼ mile or so approx 1420’ although radar emitters in the right conditions can accurately detect speeds up to 1+ mile away and are accurate at distances less than ¼ mile as well) Because two out of the three legs of the triangle are known, and one of those legs is extremely short in length relative to the other known leg, the accuracy of the radar emitter is within one or two mph of the actual vehicle speed. Assuming of course the radar emitter is properly calibrated.

Out on the water things become far more difficult to measure speed accurately with a radar emitter. There are too many variables. The primary issue with using radar as a tool to enforce a speed limit is that distance and bearing of the target vessel is not fixed relative to the radar emitter. Boats do not travel in straight lines or in fixed lanes like cars do. I have attached another diagram to help explain. Although the radar emitter will give the MP Officer a speed readout, it will not be accurate because distance and bearing (direction of travel) relative to the radar emitter are unknown. It will actually give a slower readout than the actual speed of the target vessel. If the radar readout is not accurate, you will not be able to use it in court of law. It’s a simple geometry problem and you cannot accurately solve the equation with those two unknown variables.

There are many other variables to consider as well, here are a few of the more obvious.

1. The overwhelming majority of boats on Lake Winnipesaukee are made of fiberglass and short of the engine and sterndrive contain very little metal. Fiberglass is a very poor reflector of radar energy.

2. Water has a very dense molecular structure, very similar in density to concrete. This dense molecular structure can reflect radar energy, causing false readings especially when you consider that waves are in a constant state of motion and change. This is usually called backscatter.

3. Radar cannot discern one boat from another. As the radar energy leaves the emitter it forms essentially an ever expanding cone of energy waiting to be reflected back to the emitter. Because you do not know distance and bearing of the target boat relative to the position of the radar emitter, you cannot with any degree of certainty declare that the readout on the radar emitter was from energy reflected by the target boat. Indeed the radar emitter will give a reading from the first reflection it gets, rendering it useless on a busy holiday weekend in any congested area.

The only type of radar that would be of use for enforcing speed limits on the lake would be military style naval radar with target designation and tracking capabilities. However, these radars are extremely expensive to purchase and maintain, and require a dedicated highly trained officer to operate. This is an EXTREMELY cost prohibitive system, with very little benefit in cost or enforcement.

The Marine Patrol is understaffed and under funded as it is. It is primarily a seasonal agency tasked with keeping the waters of the state safe. It would be an undue burden on the Marine Patrol and the Judicial system to enact legislation that will do nothing but clog the courts with winnable appeals, thus rendering the speed limit moot.

The biggest issue with the lake is the large amount of people who enjoy the lake on any given weekend in the summer. There are more boats of all types on the water, so there is a perception that the lake is overcrowded. The speed limit does nothing to ease this situation and essentially singles out one type of boater, the go-fast boater, who is a member of an extremely small percentage of boats using the lake.

The reality is, If you stay away from the busier parts of the lake, Meredith, Weirs, Wolferboro & Alton the lake can be extremely enjoyable and alot less crowded.


Woodsy