3P Cruising in British Columbia
by Geoff Sanvido and Dave Ferguson
In the early 1990s the TimberWest Company started a program on its
private forest lands of individual tree harvesting. We wished to remove
approximately 15% of the stand volume at 15 year intervals. The
responsibility for marking and estimating the volume and value of the
harvest trees fell to the cruisers. We determined that Variable Plot
cruising might not give us the most accurate answer. It was at this time
through our contacts with the BC Coastal Cruisers Supervisors Task Force
that we were introduced to 3P sampling.
In March 1994 we attended a Canadian 3P workshop put on by Rich Holmboe
and Kim Iles, where we learned the theory behind 3P, along with applying it
in the field. At this time TimberWest paid for the costs of having Rich
Holmboe develop a handheld 3P computer program specific to TimberWest's
[Editors note - this program is available commercially, and a
US version of it is used at the OSU short course in Corvallis]
Our program gathers information necessary for appraisal cruising and also
allows us to use variable length "cruiser called" grades and net
Our first application was on a selective harvest area approximately 20
hectares (50 acres) in size. The results were impressive. The cut versus
cruise comparison was within 1%. Over the next few years we were asked to
cruise several narrow strips of timber along abandoned railways and old
logging roads. With the width of these strips of timber varying from 1m to
15m it was obvious that variable plot cruising would not work. A 100% cruise
was determined to be unsuitable strictly because of the time and effort
involved. 3P was the ideal method.
Approximately 4,000 trees of several different species were cruised along
10 km of old road in two days. The 95% (t=2) sampling error was an
impressive 8% with a sample size of 135 measured trees. In addition to roads
and railways we have used 3P on very small and irregular shaped pieces of
real estate lands that TimberWest buys, sells or trades. We have also used
3P in cases where Variable Plot cruising failed to pick up high value
old-growth trees in a low value second-growth stand.
Tips and Observations
The most important item that will minimize workload is to walk the stand
prior to 3P cruising and get a reasonable estimate of volume by species. If
you underestimate the volume of a species within the project you will have
more "bingo" trees than are necessary. Another important item is
to mark the trees that have been tallied to avoid missed or double counted
We have found that using a three man crew with the callers (estimators)
on either side of the recorder works best. The callers put a paint dot on
each tree as they estimate the diameter, so when you look back at the stand
the dots are readily visible.
It is also important that you do not take too wide a swath, otherwise in
brushy or noisy conditions the recorder may not hear the estimators numbers
correctly. One must also bear in mind that the "bingo tree"
measurements are very critical. Poorly measured heights and diameters will
result in an incorrect ratio, and therefore a poor cruise result.
At present, TimberWest uses 3P on its private lands and for in-house data
gathering on public lands. The Ministry of Forests has yet to adopt this
very efficient method of cruising, and at this time 3P is not a
"permitted" method of data gathering for appraisal purposes in
We have found our 3P program easy and efficient to use on smaller parcels
of timber. It produces excellent stand and stock tables and very good
sampling errors. We would like to thank Rich Holmboe, Kim Iles and Alec
Orr-Ewing for their past and continuing support for advancing 3P timber
cruising in British Columbia.