Lasers - Possible use as a Distress Signal?

We've all held a laser in our hands , and in close range ,the beam at just 500mw+ is PHENOMENAL but how does it look from range of say... 1-10km away tho?

Cos at close range... sure .... the scattering is pretty impressive but is the scattering strong enough to be seen from afar tho?

Just wondering if a laser beam would be useful in an emergency situation , going hiking solo and all.

I've been hiking before with a 200mW 532, and tested it out with a friend across a lake at night. The beam wasn't visible but the laser where I was certainly was noticeable. I've thought about it before as a SOS signal but I don't know how many people would think of it as a call for help.
Here's a good reference I found on YouTube from a long distance.
http://youtu.be/5I22h1tbE9s
Of course it doesn't hurt to bring along and learn the SOS signal in case something does happen.

a 445 laser in the night would be very visible i would say, even if u stuck on a mountain somewhere the beam should be more then enough visible even far away.

You can see an 800 mW 445 from the international space station, so yes they can be seen from quite some distance...

Have a search for international space station on LPF. :beer:

Edit: there was also a recent story of some people getting rescued off the coast in the uk, because the coast guard were able to locate them via their laser pointer (signalling device)!

Edit 2: One is also legally allowed to signal an aircraft with a laser in an emergency situation. This is often omitted when people discuss planes and lasers.

Only if you're looking down the beam, it's not very visible at all from a distance otherwise.

Things said:

Only if you're looking down the beam, it's not very visible at all from a distance otherwise.

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ahh bugger nuts.
That means if we were gonna use it as a signal we have to point it at someone then.
Risking...blinding them and not wanting to save us lol

Things said:

Only if you're looking down the beam, it's not very visible at all from a distance otherwise.

Click to expand...

uh i dont believe this, if you focus the laser beam it should be very visible..

Things is right, you only see the beam due to scattering. The further away you get the less visible the beam will become. Looking down the beam the photons are comming directly at you, minus scattering/atmospheric absorption losses.:beer:

Things said:

Only if you're looking down the beam, it's not very visible at all from a distance otherwise.

Click to expand...

It depends on what laser it is.

But to say indefinitely that a laser wouldn't be visible from afar is wrong.

My cousins from over 5km away have often remarked to me how they can clearly see the beam of my 445nm laser when I point it into the night sky.

If you want to see what it looks like, just look at YouTube videos, there are a lot of long distance 9km+ videos of lasers.

will manners said:

It depends on what laser it is.

But to say indefinitely that a laser wouldn't be visible from afar is wrong.

My cousins from over 5km away have often remarked to me how they can clearly see the beam of my 445nm laser when I point it into the night sky.

Click to expand...

Think of their distance from the beam vs the distance to eg a space station.:yh: The intensity will also depend on your viewing angle relative to the beam. Try it out; look along the beam and then move around perpendicular to it. You will see that it gets dimmer as you approach 90°. If you remain at 90° and move away it will become less visible as the scattered light acts as a point source and not a coherent light source. Its intensity therefore has an inverse relationship to the square of the distance. This is called the "inverse square law". Things isnt wrong.. :beer:

While a green laser might work, your message is limited. If you're hurt, how does anyone know you're hurt and not just playing with a laser? I guess you could send SOS in Morse code, but if the person seeing that doesn't think, the message might not get through.

If you mush hike solo, this seems like a better system:

SPOT gives you a vital line of communication with friends and family when you want it, and emergency assistance when and where you need it. And since it utilizes 100% satellite technology, SPOT works around the world - even where cell phones don't.

SPOT Personal Tracker, Outdoor Safety GPS Tracker, Emergency GPS Locator Device from BackCountry Adventures in BC Canada

https://www.hightechredneckmarketing.com/outdoorsafetygps/ssl/contactus.htm


Bob Diaz

FYI it is NOT illegal in USA to lase aircraft IF truly in distress- & I am guess that means SOS- or just flashing if they are close- green wins hands down- as 50mW 532 = 1W of 450 by eye.
So its a good thing that some lasers and LED flashlights flash S O S- just dont blow your battery when help is TOO many miles away- A waterproof 100mW 532(and spare batt) would be something any adventurist needs if they dont have GPS rescue -- or for worst case..

Yeah if you go hiking or just like to always be prepared keep a decent powered green laser with you and lase some aircraft if you are in an emergency situation. They will let police know your location so you can get apprehended and then let go when they realize you were gonna die

better to be arrested than lost forever--

but I read the 'clause' in the newest law and rescue is an exception-
EDIT does everyone these days know how to S O S? I wonder??
so-- its Morse Code it means save or ship or save or souls (et al) depending upon who you ask the 'S' is three 'dots' the O is three 'dashes' thus ... --- ... repeat until rescued--


Wonder if any that got busted w/ lasers tried to say they were in need of rescue.

one of the most common was '' trying to see if the laser shined that far-" derp

we have a thread on-going on this in the welcome section- hope that newcomers, being far more likley to do the dumbass move than those who have been here a while- would stop lasing at all at night 'in public'

- ask any convicted felon how his crime changed his life overnight-- yer furbarred--
... check out laserpointersafety.com--

lots to read and heed there- please also see the YTube vid- give it the thumbs up and leave a comment- read the lyrics (in the thread and at YTube while watching- this 'cartoon' is aimed at the group where most offenders are found- male white teens---
the huge sucess of 'Dumb ways to Die' ( something like 80 million views) was made the same way - spread the link everywhere you can- this forum does NOT need convincing - its the rest of the fricken world- put the link out!!

takes the same energy as forwarding all those funny pics
but this is NOT funny
and NOT like the last 'scares' - this one has a good chance of passing-

so aside from the asshats with lasers we need to convince every one who has a say in law-making to realize, that, we nor our lasers are the problem-

- in fact we have the most power to make positive change- & that is easy to say as aside from us- there are few who have any real idea of what we do-- I have started to see PSAs on lasers just one-
and way overdue-

did you know this? -
you can get funded to make a PSA by a govt grant- how could anyone see such a PSA as something not worthy of a fricken grant - The danger of driver/pilot distraction causing a accident with death is very likely- road ragers will arm themselves with lasers-& handgiuns or guns with lasers-(something i bet all law enforcement thinks already ) IMO its not IF but when-
some of us may use our lasers to save a life
or fend off a bad guy--

-NOT GOOD-



I have a JL Ti-B 200mW 532 in my consule- of my car-

hak

Keep in mind the extreme sensitivity of the human eye--the eye can detect as few as two photons entering the retina, and that, under ideal conditions, a healthy young adult can see a candle flame theoretically from 30 miles away