Gap Light Analyzer

Gap Light Analyzer User Manual
(1.5 MB)

GLA 2.0 is imaging software used to extract forest canopy structure and gap light transmission indices from true-color hemispherical photographs


  • Scientific software (Windows 95/98/NT/7/8/10) to import, display, and analyze digital hemispherical canopy images.
  • Includes "region of interest" image-processing functions: e.g., image threshold, brightness, contrast, colour fill, etc...
  • Designed to process large numbers of photographs taken from numerous sites - individual configurations can be created for different camera lenses and orientations, regional climatic patterns and growing seasons, and topographic settings.
  • Extracts canopy structure data (gap fraction, canopy openness, effective LAI) and gap light transmission indices. Also provides a number of stand-alone utilities that will compute and display daily extraterrestrial radiation, sunfleck duration and frequency distribution, solar positions and intensities, and sky-region brightness.
  • view screenshot

Modelling and Application Design
Gordon W. Frazer , Simon Fraser University, Burnaby, B.C.
Dr. Charles D. Canham, Institute of Ecosystem Studies, Millbrook, New York

Software Engineering
Dr. Pamela Sallaway, Spatial Solutions, Inc., Victoria, B.C.
Dimitri Marinakis, University of Victoria, Victoria, B.C.

Project Funding
Forest Renewal BC Research Grant to:
Dr. Kenneth P. Lertzman, Simon Fraser University, Burnaby, B.C.

Copyright (c) 1999: Simon Fraser University, British Columbia, and the Institute of Ecosystem Studies, New York.