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Search Strip Widths

When searching an avalanche for a transmitting beacon (i.e., the "signal search"), the distance between your zigzagging paths is called the "search strip width." A wide search strip allows you to cover a large debris field more quickly, but you risk reaching the bottom of the avalanche without receiving a signal. A narrow search strip ensures that you'll receive a signal, but it will take longer to search the entire debris field.

Calculated versus Recommended Search Strip Widths

IKAR is an international organization that provides recommendations for mountain rescue know-how. They recommend that transceiver manufactures publish a recommended search strip width that is "about equal to 1.4 (± 0.1) times the realistic maximum range..." That distance is intended to allow for sufficient overlap between search strips.

The following table shows the average ranges that were measured during my range tests, the calculated search strip width (i.e., the measured range multiplied by 1.4), and the manufacture's recommended search strip width. You can see that all of the manufacture's search strip widths are well within the calculated values (although the Zoom+'s recommended width is very close to its calculated width and the Tracker DTS is fairly close).

Search Strip Widths
  Measured Search Strip
Transceiver Range Calculated Published
Tracker DTS 34 48 40
Ortovox Zoom+ 31 43 40
Ortovox 3+ 36 50 40
Tracker (T2/T3) 42 59 50
Pieps DSP (ave.) 45 63 50
Mammut Pulse 54 76 50
Ortovox S1 50 70 50

Alternatively, the most recent recommendation from the American Institute for Avalanche Research and Education (AIARE) is 30 meters without reference to any particular combination of beacons. This is shorter than even the shortest of all of the published search strip widths for any current beacons, but it accounts for perpendicular alignment, older digital beacons with shorter search ranges, and our inability to accurately estimate distances. I think 30 meters (100 feet) is an appropriate distance (and even shorter for Tracker transceivers).

Practicing Search Strip Widths

These two drills will improve your search strip width knowhow. You'll first want to decide what search strip width you plan to use. If you're unsure, choose 30 meters.

  • Stand at what you think is the selected search strip distance from an object. Now take a long tape measure (or your avalanche probe) and measure the distance. Was your estimate accurate? You should do this drill frequently and challenge your friends to estimate the search strip distance.
  • Put a transmitting beacon on the ground and stand one-half your selected search strip width from the transmitter. Using one-half the search strip width ensures that you'll have sufficient overlap when searching. Now hold your transceiver so your antenna and the transmitting antenna are aligned in "worst case" (i.e., perpendicular to each other, like a "T"). You should receive a signal. If not, you need to shorten your selected search strip width.

When in doubt, make narrower search strips. The minute or two you lose making narrower strips won't kill your friend; having to search the avalanche again, might.

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