Usefullness of a signalmirror in the mountains

Is a signalmirror usefull if you are above the snowline? I think it would be ineffective due to all the reflecting light from the white surfaces, but i'm not sure. I however do not know of any alpine climbers carrying a signal mirror...

Its the flash that attracts attention - Besides they are so small and light. I'd carry one.

i'm just not sure if the flash would attract attention, since everything is flashy in mountains.

I'm trying to shave off weight of mine equipment and every gram counts. So i'm really critical on everything i carry and it's usefullness.

I have used a signal mirror with great success in high snow conditions. The polycarbonate mirrors are less than two oz; if you carry a compass that contains a mirror, that mirror can function for signaling. While it cannot be aimed as easily as a dedicated mirror, it will serve.

It is the flash that counts....

I have seen signal mirrors from the air and used them many times in all sorts of snow conditions - High alpine in the Rockies, Tundra in Alaska and Canada and Glaciers in Alaska and the Antarctic. They were commonly used for aircraft to find the field parties before lightweight radio's. I am sure that they still work as well today. They are much lighter than a radio.

Respectfully,

Jerry

p.s. I still carry one in the field and let the pilots know that if they don't hear from me to look for it - it is my primary backup.

Ah, this thread is an example of why I like this forum. People ask reasonable questions and receive good answers. Good info to have in your back pocket.

The white light reflecting from snow is glare and more diffuse than that small piece of the sun you are aiming at the observer.


Plus the persistance of the flashes at the observer, even as he moves around, will show them that it's not a natural phenomenon.

I do the same thing. For my hiking pack, I like to keep things light & simple, so I now designate the mirror on my compass as my signal mirror & camp mirror. I've found you can aim it by holding the mirror up near your face & tracking the reflection with an outstretched hand.

Keep in mind that it's much harder to use a mirror in this fashion if one of your arms is injured,

Perfectly true, the compass mirror is a makeshift, but it is way better than nothing. As Rafowell pointed out in an earlier post, an AMK mirror weighs about an ounce - not much of a weight penalty.

Thinking about the general question, I believe there is one environment where a signal mirror might be less effective - at sea or a similar body of water, at least for other vessels at your level. This is because it is fairly common at sea to experience "mirror flashes" from other vessels. With this in mind, aim several flashes in succession at an intended target - that would be unusual and should get attention.

I have heard urban legends about people using tiny regular mirrors for visual signal, but don't have personal experience. For people considering tiny regular mirrors, please go out and practice trying to hit stuff at a long distance with a tiny regular mirror. For example, you could have a buddy drive a mile away. I'm not talking about hitting a building that's 100 yards away and easily viewable. Note that you can't see where the reflection is hitting if it's hitting at a far distance. It's really a guessing game if you don't have an aiming device.

If you have the opportunity to plan beforehand, I recommend getting a dedicated aimed mirror. My confidence is about 10 times higher with an aimed mirror. If you really need a mirror to save your life, you're going to be glad to have one. They're not that expensive and not heavy.



Even then, a signal mirror is unlikely to work. While on a beach a month ago, I was imagining someone stranded out there on a kayak. When I paid attention, I realized that there were thousands of strong reflections coming off the water. The reflections while on a boat were even worse. I couldn't imagine anybody detecting a mirror flash as being distinguishable from all the other reflections. If a mirror flash were noticed, it would be mostly dumb luck I think.

<Is a signalmirror usefull if you are above the snowline?>

Only if the person you want to signal knows where you are and why you are signaling.

My sole and only problem with signal mirrors above the three line is that I am pretty pessimistic about conditions being favorable for using one when I need it. With my luck, the sun will be obscured by clouds

Above the three line, using bright colors is an excellent way to stand out and be noticed.


Still, having a signal mirror is still a good idea, and there are lots of scenarios where a mirror will be helpful. I do have the AMK mirror in my "slightly-larger-PSK" that usually goes with me anywhere except the shortest/most urban trips.

For ultralighters an acceptable compromise between functionality and weight might be the "Featherweight Signal Mirror" weighing in at 1/3 ounce and with dimensions exceeding 3"x4". It's a metalized polymer, so obviously not ideal, but possibly better than other ultralight alternatives. No affiliation.

There is another application for a mirror that makes it a bit easier to heft that extra ounce into your PSK. They are great for illuminating dark spaces.

I learned this while working with members of the Arizona state agency dealing with mine rescue. We needed to search some mine shafts and they showed up with highly specialized, technical equipment, the mirror from a medicine cabinet! It projected a very strong beam down into the shaft and lit it up far better than any lamp. I have since done the same thing with signal mirrors illuminating building interiors, cave mouths, dark overhangs, etc. Lots of throw, but no scatter whatever.....

I am from Arizona, now living in SoCal, so the sun almost always shines for me. But I understand (I saw this in print once, so it must be true) that a signal mirror still is somewhat useful in cloudy conditions.

We should hear from Rafowell soon. I am sure he will have some definitive comments.

I regard the aiming function of the mirror as critical to its usefulness.

My Dad and I experimented with a mirror once. I was partway up a 14'er and he was across the valley bottom in a meadow.
Using FRS radio he described where he was so I could aim to flash him while he video'd it. Range was about 4 miles (used GPS).

The 6th picture on this webpage shows it (poorly, using video capture)
http://coloradowreckchasing.com/YaleDC3/trips.html
CLICK ON THE PICTURE TO GET A HIGHER RESOLUTION LOOK

I found it quite difficult to keep the flash on him steadily enough that he could get it on the video. Minutes would go by without him getting flashed even as I struggled to aim it right where he was.
If I'd used a supported position it might have been better.
It was very educational how important the sighting system was.

Snow does reflect a lot of light, but not nearly to the degree that a mirror will. I don't know the real numbers, but let's say the snow reflects 15% of the sun's light. A mirror reflects 95%. Those aren't real numbers; I'm trying to illustrate the point that a mirror is vastly more efficient at reflecting the sun.

From afar, a mirror will appear as a very bright point, and as others have suggested, it's the flash that matters. If you wiggle the mirror the light from the mirror will appear to flash (much like a strobe light or camera flash) as it hits your intended target. In the wild, the reflection off of an artificial surface really stands out which is why military units go to such pains to subdue things. Notice that I said "as it hits your intended target". Aiming is critical, particularly if your target is farther away. Here is where a dedicated signal mirror will, if you'll pardon the pun, shine. A signal mirror with a proper sighting hole is far more likely to hit the target, particularly a distant target. They're very light and very compact. I like you watch every ounce (or gram if you prefer), but a signal mirror in my estimation is worth it.

It's my PLB, at 13 ounces (ouch!) that sometimes I'm tempted to leave behind.

HJ

Well put Jim. Sure, snow and ice are "bright" compared to trees in the overall amount of light they reflect, but it's nothing like the pinpoint flash of a mirror. Tjin, I would keep the mirror and look elsewhere for weight savings. And believe me, I am a "cut all the weight you can" kinda guy.

A reasonable compromise is to go with a proven, high quality plastic mirror like the ones from Adventure Medical or Rescue Reflectors. The glass mirrors are certainly brighter but the weight difference is real.

What everyone else has said, and a mirror would be useful for first aid (such as something in your eye, or a facial cut).

The best answer to your question - take a signal mirror into the conditions you describe and test its efficacy, before an emergency situation develops. It will really pay off if you ever have to use a signal mirror for real.

Please let us know how your testing turned out.

Yes.

JerryFountain and hikermor have testified to that from their personal experience, and I provide more examples below.

Ideally the signal mirror is backup for a 24 hr, all-weather radio distress signal, such as a 406 MHz PLB (PLB FAQ), which need only weigh 5.3 oz (150 gm) for the McMurdo FastFind , or 4.6 oz (130 gm) when the ACR ResQLink is available.

For the signal mirror, given your weight concerns, look at the <0.75 oz (21 gm) 2"x3" polycarbonate "Rescue Flash" signal mirror from American Medical Kits. (See Doug Ritter's description halfway down this FAQ ) It is a high optical quality signal mirror with a an accurate, "one-handed" retroreflective aimer that produces a bright fuzzy "fireball" aiming spot, as photographed at the left in my avatar graphic. The "Mini Rescue Flash", at 1.5"x2", is even smaller and lighter, but is less than half as bright, and not available separately.

Here are some reports of successful signal mirror rescue in snow/ice:

(A) 1990s?: Australian recounts use of signal mirror in Antarctic as standard operating procedure on his Antarctica field work to signal for helicopter pickup { his parties didn't even have radios - ouch!} and shares one of his personal experiences. [1]

(B) Jan 1964: Capt. Parker C. Peedin rescued in snow, while still snowing, thanks to his signal mirror, after 36 hours on the ground after his plane went down in a blizzard. He had received no response on his hand-held UHF radio, despite calling out all day. [2]

(C) March 24, 1963: Two in Yukon rescued 50 days post-crash after plane spots their mirror flash in snow, -10 F / -23 C weather. [3]

(D) Oct 10, 1943: Three on Greenland rock (Uummannarsuaq) rescued after after flashing ship for three hours with flashes from regulation metal RAF mirror. The shipboard observer initially dismissed the flashes as reflections from sunlight on ice and snow. [4],[5]

(E) Jan 5, 1910: Three on Antarctic Shackleton expedition rescued from floating ice floe by signaling Nimrod at 10-12 mile range for one hour with "heliograph" { size not stated - if this were the standard British military heliograph, it would have a 5" diameter mirror, and be as bright at 10 miles as a 2"x3" glass mirror at 5 miles.|[6]


A snowy background definitely reduces contrast, which reduces the range of detection, but a mirror signal will still be visible many miles away, as in Example E.

The closer you are, the brighter the mirror will be in contrast to the snow, and I can (just barely) spot the flash from a 2"x3" AMK Rescue Flash Lexan mirror at 22 miles 22 miles against a dark background with my naked eye[13].(Notes: (1) I recommend viewing this in "full screen" setting, (2) The video has low dynamic range, so it fails to convey the starlike brilliance of the flash.)

That's also one reason why you want a good mirror that provides a hard concentrated flash. You can test your mirror by reflecting the beam on a shadowed surface some 50 feet away. If you aren't seeing a nice round bright circle, you're not going to get as bright a beam as you could with a good mirror. My photo here, comparing the concentrated reflection from a Mini Rescue Flash with the diffuse reflection from a BCB Mayday mirror, is a graphic example:



I haven't seen any recent discussion about alpine climber use, but the US [7] , Australia [8], and New Zealand [9] all require their personnel carry signal mirrors in Antarctica, which has as much snow, ice (and mountains) as one might like. Also, the 2005 expedition to climb Gunnbjørn Fjeld, Greenland (highest mountain north of the Arctic circle) listed two signal mirrors in their equipment list [10].




False flashes are certainly an issue, as they were in Example D, and a lot of things have to come together for a signal mirror rescue. You need a mirror, you need sunlight/moonlight impinging on you, you need to hit the rescuer with the reflected light, they must be looking in your direction, they must notice the flash, they need to realize the flash is artificial, they have to conclude it is a distress signal, then they need to direct rescuers to your location.

Two things trained searchers should be looking for to distinguish mirror signals from natural reflections:

(a) Natural reflections from snow/ice will be steady - irregular flashes are more likely to be mirror signals (though they can be water or metal trash in the breeze). Sweep your flashes back and forth across the target.

(b) Natural flashes will persist for only a few minutes - as the sun geometry changes, the flash will go away (even more true for aerial searchers). A flash that "follows" a searcher is almost certainly a deliberate mirror signal. Be persistent.

Some things you can do to improve your odds vs. false flashes:

(a) Let potential rescuers know to look for mirror flashes:

One basic survival tactic is to leave a "trip plan" detailing your planned route and equipment with a reliable person, together with a time at which they should alert the authorities that you are overdue. If you are carrying a signal mirror, note in the "trip plan" that you are carrying a signal mirror and aren't afraid to use it. (The USCG calls this a "float plan")

(b) Try to make your flashes look different from natural flashes.

With aerial searchers, one advantage you have is that the beams from fixed natural objects don't "follow" the plane, and their duration will be short. For fixed observers, any natural fixed flash will only last for a few minutes, due to the movement of the sun. So: persevere - be obnoxious about it.

In WWII, naval personnel were told to look out for flashes that "followed them" as a sign of distress. Hopefully modern-day search personnel are still taught this.

(c) Get a good mirror with a retroreflective aimer.

Two reasons for this.

First, you'll put a lot more flashes on target than with two-handed methods, based on US and British military testing[12]. You don't want observers who take interest in your first flash to shrug and move on when they don't see it repeated in short order.

Second, if you do have to flash for hours to get someone to take note, fatigue is a serious issue. A mirror with retroreflective aimer can be used with one hand, close to your body, which is less stressing, and you can switch off arms.

(d) Practice. The beam from a good signal mirror is very narrow - about a third of the diameter of the retroreflective "fireball" bright fuzzy spot in a signal mirror (the fireball in a retroreflective mesh aimer is visible in my graphic avatar to the left of this post). For getting the hang of it, use a retroreflective target at about 100 yards range. I expect many traffic signs in the Netherlands are reflective. (Be very careful not to flash anyone within a mile or so who is operating a vehicle - at short range, signal mirrors are blindingly bright.)

Once you have mastered that, ideally you and a friend can practice at about five mile range, taking turns signalling each other and counting flashes seen/minute.

> I'm trying to shave off weight of mine equipment and every gram counts.

While mirrors are pretty light, if that's a concern, I'd recommend the American Medical Kits "Rescue Flash". According to my postal scale, here are the weights of some good optical quality signal mirrors with retroreflective aimers:

2.0 oz: glass 2"x3" Coghlan's signal mirror
1.4 oz: glass 2"x2" French Air Force Miroir SOS Type 644
0.8 oz: Starflash "Ultra" 2"x3" mirror ( keep it dry )
0.75 oz : Lexan 2"x3" AMK "Rescue Flash" designed by Doug Ritter [11]
0.375 oz: Lexan 1.5"x2" AMK "Mini Rescue Flash"

While the British 2"x2" BCB "Mayday mirror" is light (0.4 oz), and has a retroreflective aimer, the samples I've tried don't have good optical quality (diffuse beam).

=============================
REFERENCES
=============================
[1] Australian in Antarctica signals helicopter with mirror on hazy day.

http://www.mail-archive.com/sundial@uni-koeln.de/msg02583.html

[2] Civil Air Patrol Volunteer, April-Jun 2010, page 46.

http://www.capvolunteernow.com/media/cms/Volunteer_Apr_May_Jun_mag_MED_LOW_583C8A758FC2E.pdf
also here: http://www.salisburypa.com/buzzonefour.html

Capt. Parker C. Peedin rescued in snow in Jan 1964, thanks to his signal mirror, while still snowing, after 36 hours on the ground after his plane went down in a blizzard. He had received no response on his hand-held UHF radio, despite calling out all day.

[3] "I Found the Girl Lost in the Yukon" Rome News-Tribune - May 19, 1963

http://news.google.com/newspapers?id=ZAouAAAAIBAj&sjid-WDEDAAAAIBAj&pg=5719,2171329&dq=mirror

Pilot Chuck Hamilton spots Ralph Flores' mirror signal Sunday March 24th, 1963 near Watson Lake, 5 miles southeast of Aeroplane lake, leading to the rescue of Ralph and Helen Klaben 50 days after they crashed.

"The brilliant sun ... glared harshly on the stark snow ... the worst of Arctic winters had fallen on the area ... Somebody's flashing a mirror at us! - I see him!" ... I located the man again, still flashing his mirror ...

[4] Fragments of war: stories from survivors of World War II
Joyce Hibbert, Publisher Dundurn Press Ltd., 1985
ISBN 0919670946, 9780919670945 Length 267 pages

http://books.google.com/books?id=HWfbUSaTB7oC&pg=PA258&dq=mirror

"For three hours and more they took turns holding the mirror in benumbed, near useless fingers for short periods while sending regular flashes.
In mid-afternoon another lucky coincidence. An American army major decided to study the Greenland coast through binoculars. At first he dismissed the flashes on Umnaarsuk as reflections from sunlight on ice and snow. But when he noticed a puff of smoke followed by the burst and fall of light from aVery rocket, he was convinced that the flashes were also signals."

[5] Down in the North, An Analysis of Survival Experiences in Arctic Areas
by Richard A. Howard, ADTIC Publication No. A-103, April 1953, Maxwell AFB Alabama.

pp. 37-38 "the rescue of the three man from Umanarsak, has been
glamorized in popular accounts by stating a 10-cent
pocket mirror was used, but the official record states they
flashed with a regulation signal mirror.

[6] The heart of the Antarctic Being the Story of the British Antarctic
Expedition 1907-1909 by Sir Ernest Shackleton, C.V.O.
http://books.google.com/books?id=VjQNAAAAIAAJ

page 252: Chapter XX: Bluff Depot Journey, Jan 15 to Feb 16, 1909

page 256:

They went back to the depot on the 14th, and pitched camp in order
to wait for the Northern Party until the 25th, when they were to
make their way back to winter quarters, or signal for the ship by
means of the heliograph. On January 24-25 this party had a very
narrow escape from disaster.

p. 257 { on January 25th, 1909: From Armytage's report }

http://books.google.com/books?id=VjQNAAAAIAAJ&pg=PA257&dq=heliograph

" I sighted the Nimrod under sail, ten or twelve miles out. We laid the heliograph on to the vessel, and after flashing for about an hour got a reply."

p. 258 { on January 25th, 1909 }

http://books.google.com/books?id=VjQNAAAAIAAJ&pg=PA258&dq=heliograph

The Nimrod stood out into the sound, and from a distance of ten or twelve miles a heliograph was seen twinkling near Butter Point. The ship was able to get right alongside the fast ice, and picked up Armytage, Priestley, and Brocklehurst.

[7] Field Manual for the United States Antarctic Program
http://www.usap.gov/travelAndDeployment/documents/USAPFieldManual.pdf
single person survival bag contains signal mirror: p. A-18
double person survival bag contains signal mirror: p. A-20
Palmer Station Survival Cache contains signal mirror: A-33

[8] "Minimum equipment to be carried on any Antarctic trip"
http://nla.gov.au/nla.arc-10243-20020607-0000-classroomantarctica.aad.gov.au/materials/clothing.pdf
Requires in "remoter areas" of Antarctica: "signal mirrors"

[9] New Zealand Antarctica manual:
http://www.antarcticanz.govt.nz/images/downloads/publications/field_manual_2010-11.pdf
both single and double person survival bags contain signal mirrors: pp. 129, 130
Value of signal mirror: page 56
One page survival card: page 7 of pdf

[10] http://www.explorers.org/flag_reports/051laughton2005.pdf

"The two aims of the expedition were to make a number of first ascents of unclimbed mountains in the Watkins Mountains in Greenland in the area of 69° North and 029° West and to climb Gunnbjørn Fjeld, 3,673 m, the highest peak in the Arctic."

On their page 18 gear list (in addition to a PLB and an Iridium phone) they list: Heliograph aircraft signalling mirror, BCB military, quantity 2

[11] AMK "Rescue Flash" mirror weight per my postal scale, last evening, including clear envelope and protective film.
Flashes from the 2"x3" AMK at 22 miles (no snow/ice) here: http://www.youtube.com/watch?v=4JtfpaMiUqQ
Doug Ritter's story of the "Rescue Flash" mirror development here (search for "signal mirror")
http://www.dougritter.com/amk_psp_faq.htm
How to use the "Rescue Flash" (or other mirror with retrorefective aimer)
http://www.dougritter.com/psp_rescueflash.htm
Another set of instructions:
http://www.equipped.org/pp/pic2042.htm

[12] The US testing by the National Bureau of Standards and US Coast Guard is reported in the article in the USCG Air Sea Rescue Bulletin attached here: http://forums.equipped.org/ubbthreads.php?ubb=showflat&Number=197058#Post197058


[13] 22 mile Sun Flash from 2"x3" Plastic Signal Mirror (best in HD, full screen)
http://www.youtube.com/watch?v=4JtfpaMiUqQ

I knew rafowell would come through for ya! Great post dude.

No affiliation, I have a Vector 1 Mirror (second mirror down on that page).

Since weight is a concern here, that mirror only weighs 1 oz., and is real glass wrapped in a permanent acrylic case. The other glass mirror on that page, same size, weighs 2 oz. There's also a "featherweight" mirror on that page that weighs 1/3 oz., but I have not handled it.

Maybe rafowell or somebody else can speak about the performance of that Vector 1 versus other mirrors. I'd like to know myself.

Really good post, Rafowell. Nice to know the AMK's are a good mirror. Shame about the BCB one.

HJ

Indeed Rafowell, very informing.

I knew the BCB's are rubish. Used to own several, because i could get them for 50 cents a piece. Good enough to annoy people at several hunderd meters, but the thing scratched like you would not believe and was clearly not as good as other mirrors.

Well, it was sunny today, so I did some testing.

My results: the AMK Rescue Flash is brighter, lighter and thinner than the "glass in acrylic" mirror - the one advantage of the "glass in acrylic" mirror is that it floats, unlike the Rescue Flash.

I tested:

• Four Coghlan's 2"x3" glass in acrylic "Sight Grid" mirrors (1.125 oz (32 gm) in provided envelope)
• A Vector 1 2"x3" laminated glass signal mirror (1.875 oz (53 gm) in closed-cell foam case)
• An American Medical Kits 2"x3" Lexan "Rescue Flash" mirror (0.75 oz (21 gm) in protective envelope)

Let's define some terms, first. Vector 1 is a wholesaler that makes:

• retroreflective mesh for signal mirror aimers,
• laminated glass signal mirrors ( 2"x3", 3"x5", 4"x5"),
• acrylic-encased glass signal mirrors (2"x3"), as well as non-signal-mirror items.

Vector 1 supplies Coghlan's with these 2"x3" mirrors branded for Coghlan's:

• Coghlan's Survival Signal Mirror #9902 (laminated glass)
• Coghlan's Sight-Grid Signal Mirror (acrylic encased glass)

Both types Coghlan's sells are available direct from Vector 1, and the link you provide is to a retailer of the Vector 1 version of the Sight-Grid mirror. Since the first four sight-grid mirrors I found were the Coghlan's branded ones, I tested them - they should be equivalent to yours. ( I do have some of the Vector 1 branded ones around here somewhere ...)

The thinking behind the Sight-Grid mirror is to provide a buoyant, lightweight mirror via the acrylic case and closed-cell foam, while retaining the reflectivity of the glass. (Interesting historical note: this type of encased signal mirror was invented by Ehrsam , who also invented the "Woodsman's Pal", which was issued during the Vietnam War as "Survival Tool, Type IV".)

My understanding is that Vector 1 retroreflective mesh is used in all Vector 1, Coghlan's and American Medical Kits mirrors that use retroreflective mesh. (Rescue Reflectors makes their own mesh, and the S.I. Howard MIL-M-18371E mirrors use legacy 3M fiberglass mesh). So, as far as the mesh itself goes, there should be no direct difference between the types I tested today.

One unique feature of the Sight-Grid mirrors is that the sighting mesh lacks the clear central sighting hole punched in the mesh used in other mirrors. While the continuous mesh might avoid some difficulties occasioned because the "fireball" can only be seen in (or right next to) the mesh it comes at the cost of additional obscuration of the target during acquisition.

While the Sight-Grid mirrors I tested had nice tight beams, the four I tested didn't seem as bright as the single AMK Rescue Flash mirror I compared them to, and definitely not as bright as the Vector 1 2"x3" laminated glass mirror. Here's the pix (note that the left and right side are different exposures - compare top to bottom, not left to right:

One of the four Sight-Grid mirrors had a beam a bit wider than the others (looked as though the acrylic case was slightly non-parallel with the glass mirror), but that was not the one chosen for the photos above.

While I didn't provide a direct "side to side" above, the laminated glass mirror was brighter than the Rescue Flash mirror.

I see your point about wave flashes - they are quite evident in the WWII SIgnal Mirror Training Film (11 minutes runtime), for those of us who haven't looked lately.

However, the U.S. Coast Guard, whose job it is to rescue you at sea, advises that you carry a signal mirror with you when at sea, and there's lots of other evidence that it is a good idea (see below). So, I'm thinking there are mitigating circumstances here.

Perhaps some of the folks here who've worked maritime SAR can comment?

The U.S. Coast Guard Auxiliary says: "the first item we recommend you attaching to your PFD is a signal mirror"

U.S. Coast Guard personnel aren't allowed to get underway unless they are carrying their signal mirrors (and EPIRB, flares, whistle ..., but the mirror is a hard requirement).

Commercial and passenger ships worldwide are required to stock their lifeboats with signal mirrors under the SOLAS treaty.

The US Coast Guard daylight search guidelines call out a 5 nm sweep width when searching from a Coast Guard cutter when the survivor has a "sun signal mirror" vs. 4.6 nm for handheld orange smoke when the watchman is fresh, and 2.8 nm after he has been on duty for 3 or more hours[1].
(Per page 3-19 of the above, this seems to mean that they will try to lay out a search pattern that gets within half that distance (2.5 nautical miles for the mirror), but I'd welcome clarification from one of the former/current professionals here.

(Literally) boatloads of people have been saved at sea due to their signal mirrors being seen by other boats - in fact the U.S. Coast Guard history credits their requirement for mirrors to a 1942 incident where 18 were saved by a passing vessel thanks to a mirror fashioned from a flattened tin can

The most recent example I have are the 23 rescued 3/9/2009 off Thailand when a small fishing boat "responded to the flash of a special mirror". The "special mirror" was part of the emergency equipment on the life rafts (as per SOLAS).

The oldest example I have are the 50 saved from the Galway Castle in 1918.

[1] COMDTINST M16130.2E 21 SEPTEMBER 2009 (8.7 Mb)
U. S. COAST GUARD ADDENDUM TO THE UNITED STATES NATIONAL SEARCH AND RESCUE SUPPLEMENT (NSS)
To The International Aeronautical and Maritime Search and Rescue Manual (IAMSAR) Sept 2009
Table H-20 Visual Sweep Width Estimate for Daylight Detection Aids (Page Page H-38)
{ Calls out a 5 nm visual sweep width for sun signal mirrors, 4.6 nm for handheld orange smoke when searcher is fresh, 2.8 nm after searcher has been on watch 3 hours. }

I was out walking the dog late yesterday afternoon, just minutes before sunset, in the hills above my house, where we have a good view out to sea. Bingo! - There it was - a distinct mirror flash, on the horizon, just in front of Anacapa Island. Shortly, another flash, and then - nothing... I paused, thinking of this thread, and observed for a bit. The source of the flash was not visible, and there were no flares, smoke, or any other signs of distress - nothing out of the ordinary.

I concluded that it was simply a "window flash," as I had described in my earlier post in this thread. This was apparently correct, because the usual sources have made no mention of any maritime incidents at this time.

The source of the flash was easily at least fifteen miles distant. Signal mirrors are extremely good signaling devices, but persistence and regularity are important to getting your message across.

Amen.

Great posts and info Rafowell.

As much as I like signal mirrors and carry one, my AO is not the best for this. Being in the PNW, we have overcast cloud, rain etc where we will do not see any significant amount of sun for days and sometimes weeks this time of year. Depending on where we are hiking/camping, the thick tree cover over large areas here can also really hamper any change of using a mirror if you were in the situation where you were incapacitated and unable to move.

The other potential drawback with a signal mirror even when there is sun and clear skies, is being able to attract an aircraft in remote areas where there is no commercial flight corridors (there are only a few major ones around here) is also crucial. Then again if a person out on a hike, whether it be a day or multi-day hike previously left a detailed trip Itinerary or route card with a responsible person, that would give the SAR air people ample reason to search the area you are in.

That said, this is why I carry a PLB and like anything else, be it a match to light a fire, a mirror, or whistle to attract potential rescue, these are all better options then not having a way at all.

Absolutely - a signal mirror should be a backup signaling device, not primary.

You want some form of 24/7 all-weather radio means for calling help, ideally a PLB. You will summon help much more surely and quickly that way. PLBs/EPIRBs contributed to the rescue of 1,596 people in 2009 alone, and in areas with good coverage, the cell phone is probably the first thing to try. As a licensed amateur radio operator, I also carry a 2 meter radio with builtin GPS.

Most recent signal mirror rescues occured because the primary radio system failed - malfunction, batteries, crushed in the fall, or went down with the boat.

Any visual signalling method is far from a sure thing - survivor's stories are rife with tales of ships and planes that blithely passed by flares, smoke, and signal mirror flashes. Signal mirrors also require coherent illumination, direct line of sight to the rescuer, and are easily mistaken for natural phenomena, unlike, say, orange smoke.

Mirrors, however, have an infinite shelf and battery life, are not expendable, and are extremely light and compact. After you've run out of everything else, they are the thing to try.

I focus on signal mirrors (somwhat quixotically) because I think that, while their utility is limited, there is a lot more potential there than is realized.

Where signal mirrors could be useful, all too often, people don't have a mirror, have an inferior mirror, or don't know how to use the mirror effectively.

Excellent info, rafowell. Thanks for taking the time and effort to educate us.

I've been wondering something that maybe you know the answer to...does a larger signal mirror mean a larger reflection dot or a brighter one?

And if it's a brighter one, then how would the reflection of a larger plastic mirror, say 3"X5", compare with a smaller 2"X3" glass mirror?

I apologize if the answers are obvious.

You're welcome!

At (extremely) short range, larger, at long range, brighter.

Since the expected range of use of signal mirrors counts as "long range", the textbook answer is that the larger signal mirror creates a brighter reflection, not a larger one.

More precisely, the beam of a 3"x5" mirror is in fact 2" wider than that of the 2"x3" mirror in the largest dimension, at any range, but since the overall beam is 50 feet wide at 1 mile range, the extra 2 inches is negligible.

The reason is that each point on a mirror surface illuminated by a circular light source reflects a cone of light whose angular diameter is that of the light source. The overall beam is the summed effect of the cones from each point. If the mirror is perfectly flat, the cone from any point is parallel to the cones produced by any other point, and simply offset by the separation between the the two points. So, the maximum width of the beam in this case is the diameter of the cone plus the diameter of the mirror.

In the case of the sun the cone diameter is roughly 0.54 degrees, or a 50 foot spread to the mile. Since the dimensions of typical signal mirrors are small compared to 50 feet, the dimensions of the mirror have little effect on the shape or size of the cone at long range.

If the mirror is not flat, the beam can be wider than the sun cone, but no narrower.

This is all simplistic geometric optics, neglecting diffraction, interference and atmospheric effects.


As a rule, a quality 3"x5" plastic mirror should be brighter than a quality 2"x3" glass mirror. A 2"x3" glass mirror has less than 40% of the useful area of the 3"x5" plastic mirror, and the reflectivity of commercial plastic survival mirrors is usually (though not always) greater than 40% that of glass.

This question is a bit tougher, since the reflective quality of both glass and plastic mirrors varies with manufacture and the angle of incidence of the light, and flatness plays a large role, too. However, good mirrors are flat enough that that effect is negligible, and good plastic mirrors are more than 40% as reflective as glass.

For example, 3rd party measurements of the reflectivity of the Starflash "Ultra" mirrors ranged from 60% to over 90% that of glass mirrors. The Starflash Ultra press release of 12/13/2007 said the Ultra was "over 90% as reflective as glass", and "now 50% more reflective", which implies their standard product was "over 60% as reflective as glass".

Although a 3"x5" version of the Starflash Ultra was announced, with a quoted weight of 2.0 oz (62.2 g), AFAIK it never shipped, and after ordering several and getting the "old-style" ones, I stopped trying.

Taking the press release at face value, though, with a reflectivity > 60% that of glass for the classic 3"x5" Starflash mirror, it should outshine a 2"x3" glass mirror.

Of course, a 3"x5" laminated glass mirror should be even brighter, and they are still being made.

Thank you, rafowell. I feel kinda spoiled to get answers like that for free.

Edit: Removed part of my post; I had thought I found a source for the 3"x5" Starflash Ultra but it was just for the regular Starflash.

Somewhat related, if you're stranded out there in the snow, it would be good to start a fire if you can. I'm thinking fire making skills up there would be more valuable than mirror signaling skills. The fire would perform double duty as a visual signal also. I'm not abandoning the mirror signaling, just keeping things in perspective for survival.

Good point, but if you're up high, good luck on finding any wood. A signal mirror also has the advantage of speed. You're out foraging while awaiting rescue after a vehicle malfunction/plane crash/whatever, and you hear an aircraft. A signal mirror takes seconds to employ. Try getting a fire started in time. A signal mirror is a great ad hoc, moment's notice device. Fire's great, and you're absolutely right to stress it's importance, but don't underestimate the value of a good signal mirror.

HJ

Good point on the lack of firewood above the three line! Signal fires are excellent, make one if you can.

If you're high up - above the three line - in the winter you will make an excellent contrast to the white background. Assuming good visibility, anything above the three line that isn't snow will be seen. But that doesn't help much if they think you're a rock. Your challenge becomes to be as different from a rock as possible.


Colors not found in nature is good. Movement is good. Combine them is even better. Flapping a big orange rescue bag around is probably top notch.


Remove snow from the equation and being spotted becomes much harder. Same principle of movement, contrast and colors, but the background is much less uniform and much more colorful, making everything harder.


Of course, a signal mirror is excellent on a sunny day, everywhere and anywhere.

ABSOLUTELY bring a signal mirror!

I'm in the Civil Air Patrol. The light reflecting from a mirror is significantly different from that of other surfaces. Other surfaces will make a flash as they reflect, but a light which follows the plane will attract far more attention from the aircrew and they will come back to check out the source, get a GPS fix, and send in ground teams.

On an exercise, my crew was having difficulty finding our target in the trees. The ground team target pulled out a signal mirror and were found almost immediately afterward.

In general, if you make a fist and hold it at arm's length, you will see the area which can be clearly focused on. For safety reasons, CAP aircraft will not often fly below 1000' above the ground. In hilly or mountainous terrain, that elevation will be increased.

Anything you do to make yourself more visible from the air will aid in being found. The signal mirror is great. Blaze orange stands out tremendously as soon as there's enough light to see by and also stands out more than other colors when overcast. It's not a natural color so it will also catch an aircrew's attention. A blaze orange hunting vest (3 ounces), handkerchief, hat, stocking cap, jacket, backpack, sleeping bag, etc., is also quite visible. The larger the better, but also will be heavier. If you don't particularly like orange, find items which are reversible with an orange side.

Above all, let someone know the area where you expect to be. That will greatly reduce the search area size, should you need assistance.

And a PLB doesn't hurt either -- but never depend on anything electronic.

HJ

This news story was in my email inbox and at first glance, it appeared to me as just another routine rescue of an injured hiker. Further reading suggests that an emergency (space) blanket may of been used to help signal to the SAR chopper. If this is actually the case, it was a good idea for that person to think of using the blanket as a signal device.

In this incident the stranded party was spotted when the search plane saw their shiny space blanket, which they had spread out in hopes of attracting attention.

According to the article:
This is Fail.

HJ

The road to hell is pawed with good intentions.

Apart from that unfortunate statement the lady seemed to have her head set right. No blame-game. You walk in treacherous places then you accept the risks.

Nor are the signs all that effective. Grand Canyon is well signed, but there was a recent fatality - a 600 foot fall from the South Rim at a viewpoint. That was far from the first time and it will not be the last.