Thursday, August 9, 2007

PS 66-122: Assessing climate change treatment effects with a radio control helicopter multi-spectral platform

Lynn F. Fenstermaker, Desert Research Institute and Eric A. Knight, University of Nevada Las Vegas.

A common problem for ecologists is the ability to measure treatment effects at critical phenological points-in-time at a desired scale.  Remote sensing provides synoptic coverage, but most satellite and aircraft sensors do not provide sufficient spatial resolution, are too costly, or cannot be acquired during the critical time period.  We developed a radio control helicopter multispectral platform that enables acquisition of whole plot images within a short timeframe at a reasonable cost.  A Century Helicopter, Inc. Predator Gasser model 60 helicopter was coupled with a Tetracam Inc. Agricultural Digital Camera (ADC, 3rd generation).  A camera mount specific to the ADC and helicopter was fabricated to isolate both high and low frequency vibrations.  The result is clear, high spatial resolution images (3.2 megapixel CMOS sensor) with green, red and near infrared bands comparable to Landsat TM bands 2, 3 and 4.  During late April and early May, 2006, we acquired images within two weeks of field measurements of percent green cover for ten 14 by 14 meter plots.  The multispectral images were analyzed using the Tetracam, Inc. PixelWrench 2 canopy segmentation software.  Canopy segmentation is an interactive and iterative process where the user defines the soil feature space depicted in a plot of the red versus near infrared bands.  A linear regression of the first set of percent green canopy calculated versus the field data yielded an r2 value of 0.80 (P < 0.001).  After additional training, the r2 value increased to 0.97 (P < 0.001).