Measuring tree heights with lasers

Measuring the heights of trees in the Coastal Douglas-fir (CDF) zone is quite a feat. In mature CDF forests (which, unfortunately, are increasingly hard to find), individual trees can grow up to 90 metres tall! But in the Gulf Islands, where most forests have been cut at some point in the not-so-distant past, second growth forests dominate the landscape and very few towering giants remain. This is true on some Islands more than others, with most forests on North and South Pender Islands’ still too young to be considered old growth or even mature.

To slow the loss of big trees and raise awareness about the importance of safeguarding CDF forests and associated ecosystems, Raincoast Conservation Foundation, in partnership with Pender Earth and the Pender Islands Conservancy, initiated the Pender Islands Big Tree Registry (the Registry). As a citizen science initiative, the Registry’s success is dependent upon nominations from local big tree hunters, so we have been working on developing resources and obtaining measurement tools to support folks in their data collection efforts. However, up until a few weeks ago, an outstanding concern remained: how do we measure the heights of these giant trees?

One of the most accurate ways to measure the height of a tree is to climb to its top (or as near to it as possible) and drop a measuring tape to the bottom. This method, however, should only be practiced by certified professionals. For those bound to the ground, tree heights have historically been collected using a few simple measurements and basic trigonometry, complemented by analogue tools like clinometers (measure slope).

However, once special conditions are accounted for, such as tree lean, visual obstructions etc., it can become quite challenging for an inexperienced practitioner to collect accurate measurements. Hypsometers, which use a combination of clinometer and laser rangefinder to measure distances and angles to calculate height, have now been adopted by most forest practitioners to narrow the margin of measurement error and remove the necessity of performing tedious calculations, but these often come with a prohibitive price tag that would put them out of reach of most environmental not-for-profits.

Yet, just a few days ago the Vertex Laser Geo arrived on the doorstep of Raincoast’s Gulf Islands Forest Project Coordinator.

This high-tech hypsometer was generously donated by the international field measurement tool supplier, Haglöf Sweden. With an unparalleled capacity to measure tree heights, complemented by a slew of additional handy capabilities such as measuring crown width and terrain slopes, this pocket-sized machine will drastically improve the quality of data collected for the Pender Islands Big Tree Registry.

Keep your eye out for upcoming editions of “Notes From The Field” which will be packed with information on Pender’s big trees and photos of our team learning to use the Vertex Laser Geo! 

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Raincoast’s in-house scientists, collaborating graduate students, postdoctoral fellows, and professors make us unique among conservation groups. We work with First Nations, academic institutions, government, and other NGOs to build support and inform decisions that protect aquatic and terrestrial ecosystems, and the wildlife that depend on them. We conduct ethically applied, process-oriented, and hypothesis-driven research that has immediate and relevant utility for conservation deliberations and the collective body of scientific knowledge.

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