Provided by Paul Wilson, December 1998
The automatic switch-over to "transmit" on Tracker DTS and
Barryvox VS 2000 is still controversial and was not liked by
most of the testers.
Tests carried out during one day with 12 to 14 year old
schoolgirls and boys have not been conclusive. The number of
tests was too small. The three new units and the Pieps 457
Opti 4 have been tested. The search times did not reveal
really clear differences between units. The scatter is very
large. However, Tracker DTS showed the smallest locating
error. For these tests the transmitters were only buried
30-50 cm deep.
Avalanche Links
It is basic but covers all you need to know for basic travel.
It has some great pictures that make sense of avy danger.
http://www.avalanche.org/
Comparison Test for Avalanche Beacons
The Swiss Federal Institute for Snow and Avalanche
Introduction
After 1990 and 1994, the Swiss Federal Institute for Snow
and Avalanche Research (SLF) in Davos organized another
international comparison test for avalanche beacons. The
test "LVS-98" was carried out under the auspices of the
International Commission for Alpine Rescue (ICAR). Financial
support was provided by the Swiss Council for Accident
Prevention. Various alpine clubs and organizations (from
Germany, France, Italy, Austria and Switzerland)
participated. The tests were necessary to obtain a clear
picture of the quality of the new types of beacons, all of
which have mostly digital type optical search aids.
The Purpose
The purpose was to clarify the state of the art applied, to
enable users to assess the quality of the equipment
available on the market, and to show the manufacturers the
strengths and weaknesses of their products.
Equipment tested
The tests covered five of each avalanche beacons from six
manufacturers. Three of those units were newly developed
and equipped with optical search aids and mostly digital
technology: Arva 9000 (France), Ortovox M1 (Germany) and
Tracker DTS (USA). The Ortovox M1 units came only from
a pre-production series. The other three units were of the
conventional type and were also used as reference units to
the comparison tests conducted in 1994: Barryvox VS
2000(Switzerland), Fitre Snow Bip II (Italy) and Pieps 457
Opti 4 (Austria).
Test Program
The field tests were carried out on 17 days in September and
October 1998. Well over 1000range tests and over 400
locating tests were performed on Les Diablerets(Glacier de
Tsanfleuron, Switzerland), on the Stilfserjoch (Italy), in
Allevard (France) and on the Stubaiglacier (Austria). It was
possible to run the tests on snow at three out of the four
locations. It was essential to ensure uniformity of the test
conditions as far as possible and, with this in mind,
detailed test instructions were produced and a three-man
SLF test team was assigned to attend the tests. Immediately
after the tests, those involved in the tests were asked to
complete a detailedquestionnaire dealing with such matters
as operating safety, operation, locating system, carrying
system and operating instructions. The equipment was finally
measured electronically at an approved test laboratory and
the main properties of the units checked to ensure
compliance with European Telecommunication Standards
(ETS 300 718).
Field Test Results
Effective range
The results of the field tests showed that the average
ranges of the new type units (20-30 m) are in some cases
much shorter than those of the proven reference equipment
that have ranges between 30 and 45 m. This gives relatively
small search strip widths from 18 to 21 m. The search strip
width is statistically defined so that a person buried in
an avalanche would be missed by the search no more than
twice out of 100.
Search Times
In the case of the locating tests, only the time needed for
the secondary search, that is from the first signal up to
the precise location, was measured. The transmitters were
buried 1 m deep. Of all the three new type units, Tracker
DTS came out best in search times, followed by Ortovox M1.
On the average, these two units produced shorter search
times (in the case of approx. 30 tests each) than with the
two reference units Barryvox VS 2000 and Pieps 457 Opti 4.
These results would even be a little better if the reference
equipment used was handled by people who were less well
familiar with it.
Locating Accuracy
In the tests on locating accuracy the transmitter units were
again buried 1m deep. The proven equipment turned out to be
better as regards locating accuracy but the differences are
rather small. The mean values (median) are between 34 cm
from the best unit (Barryvox VS 2000) and 70 cm from the
worst unit (Arva 9000). The scatter varies between units and
is partly quite large. The proportion of cases where the
locating error was smaller than 80 cm, was in the case of
Arva 9000 57%, in the case of Tracker DTS 67% and in the
case of Ortovox M1 71%. Generally speaking, units with
analog acoustics came out somewhat better. Arva 9000 has a
very wide scatter, reflected as well in the tests on range
and search time, clearly indicative of some problems with
delayed display of the receiving signal.
Locating Tests with two Transmitters
Searching for multiple burials produced some critical
results. The two transmitters were buried 5 m from each
other, one 0.5 m deep and the other 1 m deep. Arva 9000
failed to identify the presence of the second transmitter
in as many as 15 cases out of a total of 17. Five searchers
were unable to locate the second transmitter even when its
presence was indicated. When using Tracker DTS, 11 out of 23
testers did in fact identify two victims buried near to each
other but the location of the second transmitter could not
be identified again in 5 cases in spite of its presence
having been indicated. The Ortovox M1 came out best of the
three newly developed units: 13 out of 15 testers identified
the presence of two transmitters; and the second transmitter
could not be located, in spite of its presence being
indicated, in only one case. All the testers taking part
were very experienced. Even if it is assumed that when
members of the own party are searched for, the number of
buried victims is known in many cases, this result is still
very disappointing. Only some results were available for
the proven equipment. Using a Pieps 457 Opti 4 the second
transmitter in 3 out of 8 cases could not be located but was
found when its presence was indicated. No problems occurred
in the remaining only 5 tests with Barryvox VS 2000 and
Fitre Snow Bip II.
Further Observations
The equipment was repeatedly wrongly manipulated throughout
the 400 locating tests. In 3% of the tests, testers tried to
start searching with a unit in a state of operation with
which it would have been impossible to find a buried victim.
This percentage is quite high if we consider that these
testers were in fact trained people and that these were
staged search exercises. It is possible to figure out easily
what the situation would be in the case of a real avalanche
accident when searchers work under considerable stress. The
display showing the searcher the operation mode is
insufficiently clear on some of the beacons tested.
Rescue Time
Close interrelation of search strip width, locating time and
overall rescue time can be calculated from two concrete
examples of an avalanche deposit, a small one 30 m wide and
40 m long, and a medium sized 50 m wide and 80 m long. In
fact, greater range means a short primary search but a
longer secondary search, and vice versa. In the case of a
short range unit, the search is very quick with such a unit
on a small avalanche deposit but it takes quite a bit more
time on a large avalanche. A beacon with a relatively long
range compared with a short range unit takes only slightly
more time on a small avalanche but such a unit works much
faster on a real large avalanche.
Summary of the Field Test Results
The following table gives a summary of the test results.
Table 1: Summary of the field test results. The average
search time(secondary search) is the time from the first
signal up to precise location and represents only one part
of the total rescue time. The times are not representative
of a search on an avalanche deposit. The search in a serious
case lasts much longer. The mean location error (median
value) refers to a burial depth of 1 m.
| Receiver | Mean Range | Strip Search Width | Mean Search Time | Mean Location Error |
|---|---|---|---|---|
| Arva 9000 | 28 m | 18 m | 3:14 min | 70 cm |
| Ortovox M1 | 30 m | 21 m | 2:22 min | 48 cm |
| Tracker DTS | 20 m | 20 m | 2:04 min | 50 cm |
| Barryvox VS 2000 | 45 m | 50 m | 3:09 min | 34 cm |
| Pieps Opti 4 | 31 m | 29 m | 2.54 min | 54 cm |
In the case of all the tested beacon equipment, the strength of the transmitting field is close to the maximum permissible standard value. This results in an encouragingly long transmitting range for all the units. This reach is reduced only marginally at low temperatures (-20°C). On the other hand, the effect of the battery condition is slightly greater than that of the temperature.
Figures equivalent to a 10% reduction in range were found by measurement. Battery life in the "transmit" operating mode was around 300 hours in most units, varying from 180 hours (Tracker DTS) up to 700 hours (Barryvox VS 2000).
Testing receiver sensitivity the greatest differences were found not only between the units from various manufacturers but also within the same make. While the results of laboratory measurements carried out on Arva 9000 and Barryvox VS 2000 were clearly satisfactory, receiver sensitivity figures found by the test laboratory for Pieps 457 Opti 4 and Ortovox M1 compared with the ETS standard were inadequate by a narrow margin. Receiver sensitivity values in the case of Tracker DTS, measured by an accredited electronics laboratory, were found to be far too low.
Good grades for the locating system of Ortovox M1 are due to the assessment given to the proven acoustic part; on the other hand, the optical search aid is described in many comments as unsatisfactory. Tracker DTS, its handling in particular having been given lower grades, is second best from among the new type equipment. The Arva 9000 with its locating system having also been given an unsatisfactory average mark, is clearly the worst.
From a total of 50 questions, Barryvox VS 2000 is described as unsatisfactory on only two points; Pieps 457 Opti 4 and the new Ortovox M1 have 3 unsatisfactory points, Fitre Snow Bip II 6 points and Tracker DTS 8 and Arva 9000 22 points with an unsatisfactory average grade. So the well-proven reference equipment is not free from imperfections as well. For example, the testers' opinion of Barryvox VS 2000 was negative as regards its size, weight and price, and the automatic switch-over.
In spite of the fact that advanced features have been introduced to user controls in all three units (optical search aids based on a digital system) and, in the case of Ortovox M1 and Tracker DTS, the search time has also been improved, all three units still have some imperfections. They affect particularly the search for multiple burials (Arva 9000, to some extent Tracker DTS), the locating system (Arva 9000, to some extent Ortovox M1: optical section) and the handling (all three). In addition, for all three new beacons the search strip width is small. Accordingly IKAR's recommendation is very clear and based on the principle that vital safety equipment should not have any serious imperfections.
There is no doubt that the newly developed equipment is heading in the right direction. The new optical displays offer advantages but are frequently too extensive and in the case of Ortovox M1 even rather confusing. Features of promising solutions have been found in the locating system (Tracker DTS: two receiving antennas, best direction indicator) or in the combination of analog and digital technology (Ortovox M1). In simple situations (small avalanche, only one buried victim, shallow depth etc.), untrained persons should achieve rather better results with Tracker DTS or Ortovox M1 than with the proven equipment. The disappearance of sensitivity regulators in some cases should also be regarded as welcome. Therefore, it is to be hoped that the manufacturers will not be discouraged by the test results and that they will eliminate the imperfections soon. The true dynamism displayed by the development of the beacon equipment will no doubt lead to substantial improvements for the benefit of the user. It appears to be quite possible that further development will bring us in the near future a big step closer to the target which is easy-to-control, efficient and reliable avalanche rescue search equipment.
