--- Debbie <cyberia429-piclist@yahoo.com.au> wrote:
> Thanks for those ideas Mike. That NVE website looks pretty
> interesting too.The
> app will be - **if** it goes ahead? - to photograph cars on a country
> road.
> It's a big station abutting a nat park and they want to monitor who
> uses roads
> at back of their property by photographing vehicle rego plates. It's
> semi arid
> Outback country so I think dust will be the killer - how do you photo
> thru a
> dust cloud thrown up as the vehicle moves away? If go for a forward
> shot, you'd
> have probs with the vehicle's headlights at night. Plus
> flash/illumination
> probs. Still thinkin' about that.
> 
I suggest using IR digital camera's instead.  You need to be sure the
paint used on most plates gives adequate contrast.  You can flood the
area with IR without anyone knowing about it, no flash problems.  As
for creating a photo out of that, you could store them on a digital
media card. Would make it quick to get the data out and quick to handle
(no processing fees etc).

> Don't want to use inductive loops or anything that needs cables
> spread out - it needs to be smallish & easy to deploy so solid state 
> sensors look attractive. 
> The range of the sensor would be an issue - it needs to detect a
> vehicle from the side of the road. That's not far as we're talking 
> dirt tracks & large 4x4 vehicles mostly. don't need auto rego-number 
> reading. Hmmm ... a laser bounced  off a corner reflector is a 
> possibility, maybe. Would you say solid  state MR sensors could 
> detect a vehicle in a situation like that?

For optically based sensors sun must be considered for false
triggering. IR is not immune to this problem.  Microwave is immune to
sun problems but might be interfered with in other ways.  You might
also have a range issue for sensors. Namely if you need to detect
something over a wide area (greater than 10 meters).  Through beam for
optical is probably best for that reason. Reflective sensors have too
high of losses. Both are suseptable to sun and light interference.

Stephen R. Phillips was here
Please be advised what was said may be absolutely wrong, and hereby this disclaimer follows.  I reserve the right to be wrong and admit it in front of the entire world.


		
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