GRS Densitometer

GRS Densitometer: Precision Canopy and Cover Mapping, Redefined.

The GRS Densitometer™ is the most accurate and cost-effective handheld tool for comprehensive ecosystem sampling. It enables vertical and horizontal measurement of any landscape feature—from canopy layers to ground cover—delivering objective, repeatable data that other methods can't match.

Angled sighting mirror and offset leveling vials allow you to vertically sample forest canopies for a variety of coverage characteristics (e.g. canopy structure, coverage by tree size and species, and percentage of conifer/hardwood). Use to determine non-tree characteristics of sample areas (e.g. percentage of shrub/herbaceous coverage and the ground’s condition/soil type). Results are concise, objective and repeatable between observers.

The GRS Densitometer™ is a handheld sampling tool that can be used to develop estimates of vegetation/landscape-feature cover. The GRS Densitometer™, when used with either line-point or line-intercept transect sampling, combines horizontal and vertical vegetation sampling, thereby enabling the collection of comprehensive natural resource information across the landscape (horizontally) at different canopy levels (vertically). This technique provides estimates of cover for any element of any ecosystem including trees, shrubs, herbs, graminoids, non-vascular plants, down-woody debris, fuels, snags, and different ground surface conditions.

"... most accurate, least expensive, and most easily applied..." - The line-point transect method of sampling has been shown to be accurate, objective, and repeatable be tween observers. Just recently, the Food and Agriculture Organization of the United Nations concluded in a research study of four different methods of assessing canopy cover characteristics that the line-point transect was the "most accurate, least expensive, and most easily applied among the four methods tests.  This method is scientifically accurate and records forest canopy and floor cover as a set.  The instrument used in this method, the GRS Densitometer™, is small, light and easy to carry and comparatively cost efficient."

The difference between the GRS Densitometer™ and a spherical densiometer

The GRS Densitometer™ is used to estimate canopy cover and abundance within an individual sample area along a transect. In contrast, a spherical densiometer estimates what is now widely considered canopy closure at a single point location. Canopy cover is a vertical projection measure, as would be seen on an aerial photograph or satellite image. Canopy closure, however, is based on estimating the oblique coverage of the canopy, indicated by the number of covered squares counted on the instrument's mirror at a single location (Jennings, Brown, and Sheil, 1999).

As a result, estimates from a spherical densiometer are generally higher than those from a vertical sighting device and tend to overestimate canopy cover levels if used for that purpose instead of estimating canopy closure (Robards, Berbach, Cafferata, and Valentine, 2000). Furthermore, when used with linear transect sampling methodologies, the GRS Densitometer™ enables users to easily develop percent cover estimates by species, size class, and canopy position, as well as for landscape features like ground surface condition. Such detailed and comprehensive estimates are virtually impossible—or far too impractical, time-consuming, and inaccurate—to obtain using a spherical densiometer.

The GRS Densitometer™ has also been found to be useful in the estimation of visual obstruction, based on the amount of horizontal cover observed surrounding a feature, such as a Northern Bobwhite nest.  By sighting horizontally (backwards through the densitometer) in different directions radiating outward from the nest (feature), a measure of visual obstruction was developed that used to relate nesting success to the vegetation present in the vicinity of the nest (feature) (Moore, S., 2010).

TransIn Software 

Densiómetros, densitometers, densiometers, densiómetro, Densiometers

Documents

User Manual (English)