At 05:50 PM 17/01/99 -0800, you wrote:
Mark,

An interesting solution as the simple ones usually are. I do need to know
the direction of the boat so I can point the camera at it.

Thanks for the suggestion.


Peter

>Low-tech solution:  Black Polypropylene rope floats on water.  Let
>them wrap the stuff around their propeller shafts, pulling a bend in the
>rope out of a clothespin type clamp switch that turns on an alarm, and
>likely they'll still be there when you get there, trying to figure what
>went wrong with their prop.
>
>  I Scuba dive, and in the search and rescue group I was in, one other
>member was having problems in the Hood Canal area with some bozo playing
>slalom at full speed around her basic open water class students with
>their fast boat, "diver down" flags and all.  I suggested this to her &
>the perpetrators may now (years later) be out of jail - but I doubt
>they'll do THAT again.  She put 4 flags up & just added rope between the
>flags...  Might work for you.
>
>  Mark, mwillis@nwlink.com
>
>Peter Grey wrote:
>>
>> I wonder if anyone can help. I have an application where I wish to
>> photograph a boat and people at night (IR camera) but need to be able to
>> detect that they are there and in which direction (so I can point a camera
>> at them). This is to monitor offshore property. I need to get a range of
>> some 100 metres reliably. Hydrophones have been suggested but I am concerned
>> about directional capabilities and possible interferences. Does anyone have
>> any ideas in this field?
>>
>> TIA,
>>
>> Peter Grey
>> Neosystems
>
>