- October 15, 2017
- advanced riding, intermediate riding, safety
- by Chris Mayer
Don’t Skip Pinpointing using Probe!
In conducting an Avalanche Rescue, you may be tempted to start digging after you have found a lowest number with your transceiver. Here is a technical example and practice exercise to highlight why you shouldn’t skip pinpointing using your probe.
There are 4 distinct and deliberate search phases in the Avalanche Rescue* process:
- Signal Search1
- Course Search2
- Fine Search3
- Pinpoint Using Probe4
At the end of the Fine Search, we have completed a systematic bracketing pattern to find the lowest distance to the victim’s transceiver. There is often a temptation for rescuers to immediately start digging at the end of the Fine Search if they assume the victim is straight below the lowest number displayed on the transceiver.
In real scenarios however, the buried victim might not be directly below the lowest number found due to factors such as:
- the transmitting antenna’s orientation
- the burial depth
- distortions induced by the snow and the soil
For an example of a deep burial at an angled orientation, consider this overly simplified** diagram for illustrative purposes: In figure 1, the horizontal oriented transceiver (Orientation 1) produces a flux pattern so that the strongest signal found is indeed right above the buried transceiver. With the transceiver oriented at 45-degrees (Orientation 2), however, the strongest signal found is not directly above the buried transceiver and the victim could be missed if digging was commenced BEFORE pinpointing with a probe was done. Digging by far takes the most time in the rescue process. Do not waste precious time and energy by digging in the wrong location because you didn’t confirm a victim’s location by pinpointing with your probe.
It is important to note that transceivers with three antennas greatly reduce, or eliminate spiking (where the transceiver mistakenly points to a location laterally to the victim). Every transceiver resolves spiking differently so practice to understand how your transceiver behaves in different situations.
Every transceiver is different and it is important to understand how YOUR transceiver behaves in different situations and orientations. In this exercise, practice your Fine Search3, or bracketing, while seeing how your transceiver behaves when the ‘buried’ transceiver is at different orientations.
With two transceivers (borrow one from a friend then convince them to do the same exercise), ‘bury’ the borrowed transceiver by placing it a known point below a table or bed and see how close to directly above that known point your transceiver finds it’s lowest distance.
Try this for several orientations. Below are my results.
1st Orientation: Horizontal
Result: The lowest distance was 1.1 meters and was indicating to the left of the actual location.
2nd Orientation: Vertical
Result: The lowest distance was 1.0 meters and indicating to the right of the actual location.
3rd Orientation: 45 Degrees
Result: The lowest distance was 1.2 meters and indicating significantly left and down from the actual location.
For a height of just one meter, three orientations at a known location returned three different locations at three different distances. The location returned on the 45-degree orientation was far enough away from the actual location that digging WITHOUT pinpointing using a probe could have missed the victim. This highlights the importance of pinpointing the victims location with a probe BEFORE digging in the wrong location.
This was for 1 meter burial and these results would only be exacerbated for a deeper burial. Go through this exercise several times; you will feel more proficient in your fine search technique and may learn characteristics of your transceiver that may not have know before.
For transceiver search techniques: https://backcountryaccess.com/portfolio/beacon-searching-101-handout/
For pinpointing using a probe techniques: https://backcountryaccess.com/portfolio/avalanche-probing-101-handout/
*The full Avalanche Rescue process starts with leader selection through to patient care and extraction. These 4 steps just represent the search phase of the Avalanche Rescue process.
1Signal Search: RUN – Using search strips to canvas the search area, looking/listening to the transceiver to find a search signal.
2Course Search: WALK – Following a transceiver signal (flux line) to get within 2M of the victim.
3 Fine Search: CRAWL – Using a systematic “bracketing” pattern to find the closest point to the victim
4Pinpoint Using Probe: Using a spiral probe pattern to identify the victims exact position, depth and orientation.
**This diagram is overly simplified and is used just to visually conceptualize for a learning audience that orientation of a transceiver does have an effect. Flux patterns occur spherically in three dimensions and it is important to note that transceivers with three antennas greatly reduce, or eliminate spiking.
Achellis, S, 2014-2017. Spikes and Deeper Avalanche Burials. Beaconreviews.com.
Edgerly, B., 2002. Pinpointing on a line: A modern technique for solving deep burials. ISSW.
N.Ayuso, J.A. Cuchí, F. Lera, J.L. Villarroel, 2015. A deep insight into avalanche transceivers for optimizing rescue. Cold Regions Science and Technology, Volume 111, pp 90-94
Tom Immat 8:10 am
Great teaching points!!