Laser ranges makes me go "hmph"

Hi guys,

i once owned a leadlight 10mW. Pod modded it until it was dead....

Now browsing the net and checking sites like wickedlasers.com &co one thing comes to my mind.
I'm a civil engineer, not much knowledge about circuits or even short circuits but some reasonable professional knowledge about surveying.

The laser retailers advertise their lasers with a range between 12 and 40 miles (19.2 - 64 kM).
Now, since some of you sure know, our once so beautiful planet is round (like a ball). At distances of about 30 kilometres, (in surveying) we have to consider and calculate the earth's curvature.

If you stand with your laser on the beach, and i drive with my boat out about 12 miles, we would still need an extra calm see to get any lights passing.

So, how can one rely on the visibilitis of those lasers? Check them from space?
Visibility of the beam or some light source. I reckon the last.

Just my thoughts.....

How can we say that a beam is visable for 40 miles? I'd have to guess mathmatical calculation. Much like the flashlight calculations for lumens and lux and so forth. It's one big algebra equation, give one number to fill in for a variable and the rest kinda come by default, I guess..

It would make sense that distance AB between Laser and watcher would be 40 miles. A points the laser with a certain elevation into my dfirection and i see it over my head.

Would work BUT definately not withj a handheld and no way in mW areas.
We are talking watts here.
I once saw a 5 Watt green laser thrown over a lake to mark some longitude in Hamburg.
THAT thing was lighting the whole area up.

EDIT:
It wasn't a 5 w. I just found this oin the site of the company:
Germany 1999
Visualization of the 10th longitude over Hamburg by a 10-Watt YAG laser beam at the occasion of the festival "Alstervergnügen".European premiere of this new type of laser system
http://www.laserland.de/de_86x/references/events/main.html

Tried to find pictures....

It really makes sense if this is what they mean or the laser is pointed at a highly reflective surface. Your elevation or the observers would have to be high. 5mw is visible from a greater range than you think. I don't recall any site saying the beam is visible.

http://www.g0mrf.freeserve.co.uk/laser5.htm
http://www.earthsignals.com/Collins/0036/

I don't know about the range of other dealers, but the range on the Wicked Lasers site is mathematically incorrect/impossible because it fails to take into account the inverse square law. That said, even a 5mW green has a massive range when being shone into the eyes of an observer (as opposed to the maximum distance the user can see the reflected dot). I can easily see the red tail lights of cars 5+ miles away from the top of a hill. A green laser is many thousands of times brighter than a car's tail light so a range of 50+ miles isn't unreasonable at all. Even so, I disagree with any laser (or light) claimed to have a maximum range since there is no such thing. The is never a point where something goes from visible to invisible, it only slowly gets dimmer over distance so it is impossible to properly define the "maximum range" of any light source.

They need to define what they mean , whether it is reflected light or directly viewed light. For reflected light a standard surface would have to be defined, such as, a matte white surface, then all lasers according to mw and divergence are tested upon that surface.

If they did that the marketing magic would be gone