 There
are several different ways to search for multiple avalanche victims. This page
explains
transceiver-specific as well as
generic
multiple burial search techniques that can be used with any transceiver.
Generic Multiple Burial Search Techniques
The following instructions explain two methods of
searching for multiple victims using any avalanche transceiver.
Expanding
Circle Technique
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1 |
Locate the first victim using the normal
search techniques. (This is the red line in the
following illustration.) |
|
2 |
Your partners will begin digging for the
first victim. |
|
3 |
Move approximately
three meters from the victim. The
distance
indicator on your digital beacon should
display approximately
three meters. (If
you have an analog beacon, turn down the sensitivity so it just picks up
the first victim.) |
|
4 |
 Slowly
walk in a circle around the victim while watching the distance indicator.
You are looking for a sudden change in the distance that is less than the
three meters you are from your first victim. Likewise, watch for a sudden
change in the
direction indicator that does not point to your first victim.
(With an analog beacon, you are listening for a second beacon.)
When a change is noted, use the
secondary
and pinpoint
search techniques to
locate the second victim. If you complete the
circle without finding a second victim, expand the circle by three meters
and again circle the first victim.
If your transceiver leads you back to the
first victim, return to the previous three meter circle and repeat the
process.
On the illustration shown here, the red
line represents your initial search path to locate the first victim. You
would then move three meters from the victim and circle the victim as
shown by the smaller blue circle. In this case, your transceiver will
continue to show the distance to the first victim (approximately three
meters), because this victim is still closer to you. After completing
the first circle you would enlarge the circle by three meters and again
circle the first victim. In this second circle you should expect the
distance to show approximately
six meters (because you are now six meters from the first victim). However,
as you near the second victim your transceiver will drop from the expected
six meters down to approximately 1.5 meters (in the above example). You should then use the
secondary and pinpoint
search techniques to locate the second victim.
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| 5 |
If a second victim is found and victims
are still missing, you should return to your last location on the circle
and complete the circle. If you complete three circles (approximately 9
meter radius) without finding a victim, you should return to your primary
search. |
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The expanding circle technique
works well and is easy to learn. The disadvantage is you have to cover a
lot of ground and walk uphill to complete the circles.
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Micro Search
Strip Technique
Details on the micro search strip technique can be
found here
 .
|
1 |
Locate the first victim using the normal
search techniques. (This is the red line in the
following illustration.) |
|
2 |
Your partners will begin digging for the
first victim. |
|
3 |
Move approximately
three meters from the
victim toward the direction that you approached the victim. Your digital
beacon should display approximately three meters. (If you have an analog
beacon, turn down the sensitivity so it just picks up the first victim.) |
|
4 |
 Now
begin a primary-search-like route,
but this time with approximately three meters between each pass. As with
the expanding circle technique,
you are looking for an unexpected change in the distance or direction relative
to the first victim.
When a change is noted, use the
pinpoint search technique to
locate the second victim. If your transceiver leads you back to the first
victim, return to your previous micro-strip location and continue searching.
On the illustration show to the right, the
red line shows your initial search path which located the first victim.
You should then move a few meters up hill and continue searching. Your directional
indicator will continue to point to the first victim and the distance will
increase/decrease as you move further/closer to the first victim.
When you are closer to the second victim
than the first victim (this is the point where the blue line changes to
a dotted
line in this illustration), your transceiver will point in a different direction
and the distance indicator will drop to display the distance to the second
victim. You can then use the pinpoint
search technique to locate the second victim.
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Transceiver-Specific
Multiple Burial Search Techniques
When there are multiple victims, the searching transceiver receives a complicated collection of signals. And as the number of victims increases, the
amount of time that the various signals overlap also increases. Modern digital transceivers analyze the rhythm and signal strength of the various signals to estimate the number and
location of the victims. These transceivers then allow you to "suppress" a specific signal. This is done by ignoring the signal based on the previously analyzed rhythm.
If your avalanche transceiver mistakenly returns you to a victim you suppressed, you should repeat the suppression process.
When there are 3 or 4 victims, it becomes almost impossible for the searching transceiver to separate the signals due to signal overlap. It
is also more difficult for the transceiver to separate the signals if the victims are located close to each other, because the searching transceiver cannot use signal strength to
help distinguish between the signals. Due to these challenges, you should still learn and practice the
generic
multiple burial search techniques regardless of the type of beacon you own. You should also reduce the likelihood that multiple people will be buried by not exposing multiple
people to the same avalanche hazard.
It is very important that you read the user's
manual that comes with your beacon and that you practice these multiple burial
techniques. None of these techniques are intuitive enough to figure out after the avalanche
strikes.
As with all avalanche transceivers that can suppress a signal, you should locate the victim with your
probe before suppressing the signal.
You can read the details of the multiple burial tests
here.
Analog
Transceivers
You can estimate the number of victims when
using an analog beacon by listening to the rhythm and cadence of the beeps. For
example, if you hear beep-beep, pause, beep-beep, you know there are two
victims (the closest beep will be the loudest). Turn the sensitivity
down to isolate the nearest beacon and then search using analog techniques. After locating the first victim, use the
generic multiple burial techniques to locate the other victims.
ARVA Advanced
The
multiple burial feature in the ARVA Advanced was updated for the 2007/2008 season. The new version uses a Mark
technique that is similar to the Ortovox S1, Pieps DSP, and Pulse Barryvox.
When multiple signals are received, the
icon appears on the screen and the Advanced locks on the
closest victim. After locating the first victim, you can suppress (a.k.a. "block") the current victim's signal by quickly switching from search, to transmit, and
then back to search (by toggling the "nose" switch). The Advanced then directs you to the next victim. This feature worked well in my testing. You can learn more
about searching for multiple victims in the user's
manual.
Optionally, you can toggle the Advanced to
analog mode (by holding both the "+" and "-" keys pressed for a few seconds)
and then use the analog multiple burial search technique.
ARVA Evolution+
When multiple signals are received by the
ARVA Evolution+,
the
icon appears on the screen and the Evolution+ locks on the
closest victim. After locating
the first victim, take "one or two steps backwards" in the direction you came,
then quickly switch from search, to transmit, and then back to search (by toggling the "nose" switch). This activates a "scan mode."
Hold the Evolution+ very still while it scans
for the transmitting beacons. The Evolution+ will then display information
about each of the transmitting beacons. It rotates through this
information approximately five times. During each rotation, the screen will
display the direction and
distance to one of the victims. Head toward one of the victims that you
haven't found. If the transceiver returns you to one of the victims you have
already located, repeat the Scan mode (by toggling the switch).
In my testing of the Evolution+ multiple burial mode, the scan mode did a good job of stating the distance to the
burials, but the direction indicator was only mediocre in pointing the
correct direction.
Barryvox 3000
The
Barryvox
3000 shows if there is one, or more than one, transmitter by displaying
a small icon. This is helpful when determining if there is more than one victim,
although the 3000 does not have any multiple burial search features. It is probably best to
use the digital search to find the first victim, and then either use a
generic multiple burial search technique or switch
into analog mode and use the analog multiple burial search technique.
Ortovox D3
An LED on the Ortovox D3 lights up if there is more than one victim. The D3 does
not have beacon-specific functionally to search for multiple victims so you should use one of the
generic multiple burial search techniques.
Ortovox S1
The Ortovox S1's approach to multiple victims is unique, because the S1 can display multiple
victims on the screen at one time. The distance to each victim is also displayed. (The Pulse can display information on
multiple victims, but not in a graphic format.)
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Mark
Button |
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After locating the first victim, you can suppress that victim by pressing the "Confirmation" button. A flag then appears on the
screen where the victim was displayed and the S1 will guide you to the next
victim.
Pressing the Confirmation button a second time will unmark the victim. In my testing
with two victims, the S1's marking and unmarking were excellent. The user manual mentions that you cannot unmark a victim if several victims are transmitting within a 3 meter
radius.
All avalanche transceivers that allow you to suppress a victim must deal with the challenges of overlapping signals. If the S1 is unable to
separate the signals and display them on the screen (as might happen when there are 3 or more victims), the S1 will reduce its reception range until the information can be processed and
displayed. If the S1 is unable to separate the signals, the "Stop" hand is displayed. You should then stand still as the S1 analyzes the signals.
If there are 3 or 4 transmitters and the S1 is unable to separate the signals, a screen is displayed showing "4+". This screen, although it is
far from intuitive, is asking if you want to limit the range to 5 meters. You can then press either the Confirmation or Rejection buttons. After confirming that you want to
limit the range to 5 meters, you should then use the expanding circle or
micro strip technique to locate the victims.
And finally, there is a "Search for more than 3 victims" mode (which can be selected from the menus). In this mode, the first victim is located
in the normal manner. After suppressing the first victim, the transceiver automatically reduces the range to 5 meters.
These additional features and icons may be difficult for the average rescuer to deal with during a life-or-death emergency, but the basic search,
mark, and locate the next victim features work well.
Pieps DSP
When multiple signals are received by the
Pieps
DSP, little men ( )
are displayed on the screen indicating the number of victims.
|
|
| Three Victims |
After locating
the first victim, you can suppress that transmitter without digging up the
victim by pressing the Mark button for approximately three seconds (until
the distance
indicator changes to "--"). A box will surround that
little man and the DSP will guide you to the next
victim.
|
|
| Victim Marked |
In my multiple burial testing with two victims (using the version 5.0
software), the DSP's
suppress feature worked very well. Earlier versions were less consistent in their ability to suppress a signal.
The Mark feature works best if you hold the DSP very still when pressing the
Mark button (I noticed this more using earlier versions of the DSP software).
The DSP also has a scan function. To enable
it, press and hold the "?" button for a few seconds while in search mode. The DSP
will then display the number of transmitters
within 5, 20, and 50 meters.
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| Victim Marking |
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| Victim Selection |
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Pulse Barryvox
The
Pulse Barryvox displays silhouettes ( )
to indicate the number of victims (up to three). By default,
the Pulse guides you to the nearest transmitter. After locating the victim, suppress the victim by pressing the
right button. This suppresses that signal and the Pulse will point you to the next victim.
The Pulse lets you rotate between the victims by pressing the left button.
As you rotate between the victims, the
distance
and
direction indicators are updated.
The Pulse also allows you to unmark
a previously suppressed transmitter (as does the Ortovox S1). The selecting of victims and unmarking requires a little learning,
but it worked great during my
multiple burial testing.
The Pulse does not display the
Mark command until you are within 6 meters. A warning is displayed if you
attempt to Mark a victim that is more than 3 meters away.
Tracker DTS
 The
Tracker DTS has a "special mode" button that narrows the reception "arc" from 180° front and
back (i.e.,360°) to 75° front and back. When you locate
the first transceiver, you can then narrow the arc and scan around the located transceiver
to see if there is another signal in the distance. This assumes that you know there are multiple victims,
because the Tracker does not display an indication of multiple signals.
This special model definitely requires
practice (and the Tracker's user manual provides limited information regarding the special mode). Learning the generic multiple burial search techniques is probably a better use of your
time.
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