[PUP] FLIR and Nauticomp display

[Mike & Denise]

Hey Ken,

I'm a newcomer here but I do have a fair amount of experience with thermal
imaging devices having been a Bradley Fighting Vehicle gunner. My experience
is that thermals don't work in thick fog or smoke. When you think about how
they work, that shouldn't be too surprising. They are looking for heat
contrasts. If you throw a great big wet blanket over everything (fog), you
do two things. First, you cool the surface of whatever maybe out there.
Second, you obscure whatever is out there with cold particles. With smoke
it's a little different, but that shouldn't be encountered much on the water
so I won't go into it.

I don't have a lot of experience with Forward Looking InfraRed (FLIR) except
as it is used on some personal night vision devices. But, I would say, based
on my understanding of how it works, that FLIR would work worse in obscuring
visibilities (fog, smoke, rain and snow) than thermal. This is because the
Infrared part is a beam that is shot out ahead of you allowing the device to
"see" what is illuminated. Infrared is not in the visible spectrum of
course, so you don't see the beam of infrared light that is being projected.
So, if you shoot the beam of infrared light into thick fog, you get the same
thing as you get if you turned on your spot light (only you paid more for
it).

My experience with night vision devices is that they work well when it is
just dark. When you throw in other obstructions like rain or fog, then
thermals are your best bet. When that degrades, you're out of luck. People
with more FLIR experience may have better info on that subject.

Mike

-----Original Message-----
From: passagemaking-under-power-bounces at lists.samurai.com
[mailto:passagemaking-under-power-bounces at lists.samurai.com] On Behalf Of
Ken Williams
Sent: Tuesday, September 04, 2007 5:07 PM
To: 'Passagemaking Under Power List'
Cc: NordhavnOwners at yahoogroups.com
Subject: Re: [PUP] FLIR and Nauticomp display

John Ford:

No idea if I'm the Ken you referred to, but your timing is perfect. I'm
sitting at anchor in the San Juans and had fog so thick this morning I
couldn't see my own tender. I have a night vision camera with two different
night modes, "Ultra Low Light", and "thermal imaging". 

Both modes were completely useless. There were six boats anchored about 100
yards away, as well as land perhaps 200 yards away. Nothing showed up,
including the bow of my own boat.

I've alerted the manufacturer (NVTI) that I am very disappointed in my unit
(the NVTi 5000). The image in a marina on a clear night isn't bad, but in
real world conditions, I have yet to find it useful. To be fair: It is going
back for service and perhaps when I get it back I will be more impressed.

-Ken Williams
Nordhavn68.com, Sans Souci

-----Original Message-----
From: passagemaking-under-power-bounces at lists.samurai.com
[mailto:passagemaking-under-power-bounces at lists.samurai.com] On Behalf Of
John Ford
Sent: Tuesday, September 04, 2007 1:42 PM
To: Passagemaking Under Power List
Cc: NordhavnOwners at yahoogroups.com
Subject: Re: [PUP] FLIR and Nauticomp display

On Sep 1, 2007, at 10:23 PM, Scott Bulger wrote:

> FOG shuts it down completely.  I couldn't see past the bow rail.

Thats interesting..  I was hoping that this wouldn't be the case at  
all.  When doing some research and reading many websites one of the  
things they touted was the ability to see in fog.  I would be  
interested in hearing if others "Ken?" have had similar issues with  
the FLIR.

John Ford
KK44 Feisty Lady(She may turn into a 48 soon).
Annapolis City Marina
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