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Modeling of Deflection in a Field Goniometer used in the Estimation of Bi-Directional Reflectance Distribution Functions

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Paper number  SD09-201,  ASABE/CSBE North Central Intersectional Meeting . (doi: 10.13031/2013.29150) @2009
Authors:   Zacharie Claude Martin, Scott David Noble
Keywords:   Model, Goniometer, Bi-Directional Reflectance Distribution Functions

A field goniometer is an instrument used to estimate bi-directional reflectance distribution functions for different types of surfaces. With the creation of the University of Lethbridge Automated Field Goniometer (ULAFG), deflections and twists in the mast, boom, and shoulder assemblies are critical to the accuracy of the camera positioning and field of view. A model of the deflection and twisting at different camera positions was created in Excel. This model gave an indication of what areas of the goniometer frame design require special attention to minimize deflection and twist and maximize positional accuracy of the camera. The results from the Excel model were compared to a COSMOS finite element analysis of the goniometer. The maximum absolute error between the measured ground locations of the field of view of the two methods in the X-direction was 0.03 cm and in the Y-direction was 0.112 cm.

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