Evaluation of forest canopy damage using airborne videography

Authors: G.P. Hosking
Publication: New Zealand Journal of Forestry, Volume N.Z.J.For. 1995, Issue N.Z.J.For. 40(1) 1995, pp 24-27, May 1995
Publisher: New Zealand Institute of Forestry

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Abstract: A recently commissioned airborne video system, based on that developed by the US Forest Service, is being used to document canopy damage caused by introduced animals, insects and disease in both exotic and indigenous forests in New Zealand. The system has a number of attributes which make it attractive for management scale monitoring and assessment of forest health problems, although its limitations must also be recognised.

In this study the effects of light quality, system setup and swath width on image quality were reviewed. Imagery already obtained for a range of forest types and canopy damage suggested that the system produces outstanding results for some objectives, but may have little application for others.

NZFRI Ltd experience during 1993-94 indicated the following positive features of the system: ability to subsample within overall coverage using a remote controlled zoom lens; high-quality imagery obtainable under a wide range of light conditions; inclusion of audio information with the video track, and ease of imagery transfer into a computer environment. However, swath width is limited by the required level of resolution, and subsampling must be carefully preplanned. Lower tree crown information is likely to be unreliable.

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