LIDAR Safety

[josephfeatherweight]

Hello learned folk,

The following appears in the NOTAMS for YMMM:
OCULAR HAZARD
ASSOCIATED WITH LIDAR LASER USE DURING AERIAL
SURVEY OPERATIONS AT GEELONG (YGLG) VIC. THE HAZARD EXISTS WITHIN
1500 FT BELOW THE SURVEY AIRCRAFT WHEN THE LASER IS ACTIVATED. LIVE
RUN BROADCASTS WILL BE MADE.
AIRCRAFT TYPE: BN2 CALLSIGN: VH-CWG.
LATERAL LIMITS: OPERATING AREA IS WITHIN:
16 NM RADIUS OF POSITION: 3809'S, 14422'E
FOR FURTHER INFORMATION CONTACT: 0429 131 163.
3200FT AMSL TO 3600FT AMSL
FROM 02 012320 TO 02 120800
H24

Is the "ocular hazard" they deem important enough to mention above, significantly hazardous that one should be concerned that they were "lased" by the green laser as the aircraft flew directly overhead? :8 Aircraft was at approximately 1000'-1500'.
Aircraft "lasing" people on the ground! That's a twist to the usual story...

Joe Lighty
Nobody's ever died from pressing...

[startingout]

A little while ago I used to fly this exact aircraft. There is a safety shutoff on the sensor within the plane which is usually over sensitive, if something below it is triggered within a set distance the shutoff comes on and then the laser is inoperative. A lot of care is taken by the crew in the event that another aircraft comes within a closer distance they switch off the system early.

There is no need to worry about the lasers from the aircraft as you will never be close enough to actually risk eye damage. The notam is there to protect everyone as we all know that we are meant to read them and take them into consideration in our flight planning.

[startingout]

Oh I forgot to add, the laser is in the invisible light spectrum.

[josephfeatherweight]

Hi startingout - thanks for your response.

Oh I forgot to add, the laser is in the invisible light spectrum.

Strange - there was a definitive flash of what I can only describe as green l@ser light - I've had the misfortune of being "lased" on approach into YSSY and to me it was the same, though obviously not scattered by a window. The flash was only instant, emanating from a black squared area on the bottom of the fuselage - it was literally directly overhead. Maybe the laser mirrors/prism (if employed) can create a green refracted flash?

If it isn't already obvious, my vision hasn't at all been affected, it was more out of interest that the NOTAM refers to a potential "ocular hazard" and I potentially was stupid enough to be staring at it - granted not from another aircraft but (worse?) standing on the ground as it overflew me.

Also, I was pretty sure the aircraft was a Chieftain, not a BN2 as per the NOTAM above (but my twin GA aircraft knowledge is pretty poor) which I copied and pasted purely for info - but it was definitely flying a grid track (back and forth) and given my experience with the "l@ser", I assumed it was a LIDAR aircraft.

[SgtBundy]

Out of curiosity, is this LIDAR as in the aerial speed enforcement you see signs for out on the highways, or just some sort of geo survey gear?

[Trojan1981]

No, survey.

Road markers and cameras are generally used for aerial speed enforcement.

[fanning]

Photo Search Results | Airliners.net (http://www.airliners.net/search/photo.search?regsearch=VH-CWG)

Looks like a bongo to me, but I've heard lidar done in titans, navajos, 172's heck even a nomad :ok:

[Horatio Leafblower]

A mob in Rocky do LiDAR in U206, A36 and PN-68 :uhoh:

[VicRod]

Thought this may be relevant, it is aan extract from a paper on similar equipment related to your post, from the people who ought to know;

The radiant output wavelengths of the airborne AURA are outside the visible spectrum as defined byANSI Std. Z136.1-2000*, ANSI Std. Z136.6-2000†, and FAA7400.2D Chapter 3, * and do not pose a visual interference (distraction, disruption, or disorientation) concern for aircrews in navigable air space. Startle, dazzle, flashblindness and glare concerns apply only to visible light and do not apply to invisible laser beams. The critical zone exposure distances (CZED) and the sensitive zone exposure distance (SZED) do not apply.

In my opinion the statements made above are incorrect, which concerns me greatly. Just because the light emitted is invisible, does not mean that it has no impact. I gaurantee that an infrared laser light can cause dazzle and flash blindness. So if many professionals in the field are unaware of the effects, they can never improve the equipment as they seek to remain ignorant to the issues, possibly for their own purposes. (maybe to avoid more calculation, knowing the outcome will not be favourable to their purposes)

The flash seen is probably a nanosecond after you were (over)exposed. Your brain has recieved a response from your eyes (the cells effectively responding to the energy exposure which has occurred), and has interpreted the signals the best way it can. Other radiation sources and fields such as solar, electircal, radio, magnetic etc may have exacerbated the background energy/receptors to allow you to see the flash.

:)

[baswell]

The boundary between visible light and infrared is not a hard one. Make the source bright enough (as l@asers by definition are) and it will be visible; much like your radio will pick up a very strong signal on a nearby frequency.

The higher in frequency of the light, the less visible it will be, to the point where it is invisible. But it is still a radiation source that can do damage to the eye, though it won't cause flash blindness.

But you'd need a heck of amount of exposure to do any damage with the kinds of power they are using for LIDAR!

[Mortuns mate Nebbill]

"A mob in Rocky do LiDAR in U206, A36 and PN-68 http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/worry.gif "

I used to work for this :} "mob in Rocky". The LiDAR equipment we used were all Class 1 Lasers LiDAR systems (see below for the defs on a class 1 laser) Notams like the one mentioned at the begining of this thread are usually posted to cover the company during ops. If I remember correctly our unsafe unprotected eye distance was 30 metres, even low level survey isn't 30 metres. :cool:

Class 1
A Class 1 laser is safe under all conditions of normal use. This means the maximum permissible exposure (MPE) cannot be exceeded when viewing a laser with the naked eye or with the aid of typical magnifying optics (e.g. telescope or microscope). To verify compliance, the standard specifies the aperture and distance corresponding to the naked eye, a typical telescope viewing a collimated beam, and a typical microscope viewing a divergent beam. It is important to realize that certain lasers classified as Class 1 may still pose a hazard when viewed with a telescope or microscope of sufficiently large aperture. For example, a high-power laser with a very large collimated beam or very highly divergent beam may be classified as Class 1 if the power that passes through the apertures defined in the standard is less than the AEL for Class 1; however, an unsafe power level may be collected by a magnifying optic with larger aperture.

Class 1M

A Class 1M laser is safe for all conditions of use except when passed through magnifying optics such as microscopes and telescopes. Class 1M lasers produce large-diameter beams, or beams that are divergent. The MPE for a Class 1M laser cannot normally be exceeded unless focusing or imaging optics are used to narrow the beam. If the beam is refocused, the hazard of Class 1M lasers may be increased and the product class may be changed. A laser can be classified as Class 1M if the power that can pass through the pupil of the naked eye is less than the AEL for Class 1, but the power that can be collected into the eye by typical magnifying optics (as defined in the standard) is higher than the AEL for Class 1 and lower than the AEL for Class 3B.