Transceiver probing, sometimes called pinpointing, takes place after completing a transceiver fine search. It is an important step to confirm that you are in the correct location before you begin digging.
After completing the fine search, you should stow your transceiver so it doesn't interfere with probing and shoveling. And after you start probing, trust your probe and avoid the temptation to return to your transceiver. The time you "waste" probing a larger area is usually small compared to the time you will waste returning to a transceiver search.
Hold the probe firmly with both hands (don't cling to your transceiver with one hand—it should be stowed). When probing for a transceiver signal, insert the probe at 90° relative to the snow rather than relative to gravity. This is because, as shown in this animated image, your transceiver will take you to the closest location relative to the transmitting beacon, which is not necessarily directly above the victim. If you mistakenly hold your probe vertically (a common mistake), the transmitter will be uphill of your first probe. (When spot probing, the probe can be held at any angle; when used in a probe line, the probe should be held vertically to gravity.)
You should first insert your probe at the location where your avalanche transceiver reported the strongest signal (i.e., the shortest distance). Subsequent probes should be in circles (or a spiral as proposed by Manuel Genswein in 2002) from this center point at no more than 25 cm (10 inch) intervals. This small distance between holes ensures that you will not miss the victim. It is better to "waste" a little time probing tightly than to miss and have to re-probe the entire area. (Ten inches is approximately the length of a man's bare foot.)
If your fine search was decent, you should find the victim within the first or second circle (i.e., within a 20-inch radius). Even if you encountered a spike (which is very uncommon with modern, three-antenna transceivers) or your fine search was sloppy (which is unfortunately common), continuing to probe every 25 cm (10 inches) will eventually locate your victim.Some manufactures suggest that you should repeat your fine search if you don't locate the victim in the third circle—I'd go for at least four circles before returning to my transceiver. (My rough time estimate is that probing a one-meter radius [which would be a huge miss] at 10-inch intervals will take about five minutes.)
If your transceiver indicates a very deep burial (e.g., more than two or three meters), your probe may not reach the victim. In this almost certainly unsurvivable case, you should dig down approximately one meter starting at your fine search location, and then reattempt to locate the victim using your probe.
When you find the victim with your probe, leave it in place and begin shoveling. Leaving the probe in place will help you stay on-target as you shovel and will remind you to not stand on the victim which might compromise his airway.