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 needs.

[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 factoring.

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 trees.

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 British Columbia.

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.