Yes, it's true that the nails were either too short or not "tapped" hard
enough. Either way it gave "odd" readings. Maybe we have to go bark to using
a forester's bark gauge to first determine the depth of bark and then use
calibrated nails, if that is the critical aspects. No doubt more testing
will reveal all in the fullness of time.
Julian Dunster
----- Original Message -----
From: "Scott Cullen" <dscottcul@xxxx.net>
To: "UK Tree Care" <uktc@xxxxxxxxx.co.uk>
Sent: Wednesday, February 05, 2003 9:29 AM
Subject: Re: PICUS
Julian, as Joe explained your Bay Area tests to me, the issue was short
nails on very thick bark. Is that your recollection? If so it may be
less
an issue of "so sensitive to the depth at which the nails are driven"
overall than of good contact with sound wood. As I understand the concept
it depends on speed of sound wave travel which is directly dependent on
density. If the software is calibrated for sound wood as the basis and
detecting less density beyond, then starting in bark, going to sound wood
and then looking for lower density may through the calculations off. Or
more basically, the instrument may need good contact with sound wood to
accurately register the transmissions.
"and as with the other setups, only gives a reading in one plane of the
tree"
True enough. But with enough time you can take multiple planes without
extensive boring damage. Orrrrrrr, you can look harder at the Wessolly
pulling tests!
SC
----- Original Message -----
From: "Julian or Kathy Dunster" <jdunster@xxxxxxxx.com>
To: "UK Tree Care" <uktc@xxxxxxxxx.co.uk>
Sent: Wednesday, February 05, 2003 12:17 PM
Subject: Re: PICUS
I think the critical point here is "... the nails being driven through
the
bark so that they are just in contact with
the latest growth ring." The test in California that I saw were very
ambiguous and did not match the Resistograph results and did not
accurately
match the sawn cross sections. We did not have an opportunity to test it
again with the nails driven deeper. If the instrument is so sensitive to
the
depth at which the nails are driven, it may yield some odd results so I
think it still needs work. It is also very expensive and as with the
other
setups, only gives a reading in one plane of the tree.
Julian Dunster
----- Original Message -----
From: "Liz Gilbert" <liz_gilbert66@xxxxxxxx.com>
To: "UK Tree Care" <uktc@xxxxxxxxx.co.uk>
Sent: Wednesday, February 05, 2003 8:12 AM
Subject: RE: PICUS
I worked on a research project to evaluate the PICUS while in the
States
last year. We used the instrument to take measurements on around 30
cross
sections of a number of trees, and then chopped them down to see how
accurate the method was in assessing the area and location of decay.
The
results looked good. In all cases where decay was not present in a
cross
section the PICUS showed no decay. In cases where there was decay it
appeared to be very accurate. It is less invasive than drilling, with
the
nails being driven through the bark so that they are just in contact
with
the latest growth ring. The results should be published at some point,
when
we've finished writing it up...
I had some contact with a guy in Germany who was also researching it
and
he
had found that it could detect decay caused by Ustulina deusta. As far
as
I
know no one in the states was using it either because of the high
cost.
Liz Gilbert
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