Field Conditions

AARGnews, 2017

Ocean color algorithms are based on the parameterization of apparent optical properties as a function of inherent optical properties. The WET Labs underwater absorption and attenuation meters (ac-9 and ac-sac-s) measure both the spectral beam attenuation [c ( )] and absorption coefficient [a ( )]. The ac-s reports in a continuous range of 390-750 nm with a band pass of 4 nm, totaling approximately 83 distinct wavelengths, while the ac-9 reports at 9 wavelengths. We performed the ac-s field measurements at nine stations in the Mid-Atlantic Bight from water calibrations to data analysis. Onboard the ship, the ac-s was calibrated daily using Milli Q-water. Corrections for the in situ temperature and salinity effects on optical properties of water were applied. Corrections for incomplete recovery of the scattered light in the ac-s absorption tube were performed. The fine scale of spectral and vertical distributions of c ( ) and a ( ) were described from the ac-s. The significant relationships between a (674) and that of spectrophotometric analysis and chlorophyll a concentration of discrete water samples were observed.

The Photogrammetric Record, 2013

The XXIInd International Congress of Photogrammetry and Remote Sensing

Applied Surface Science, 2017

Spectroscopic ellipsometry is currently widely used to describe the polarimetric response of structured media. The conceptional shortcomings of the commonly used Fresnel approach to predict and simulate ellipsometric data of structured media is discussed using numerical solutions of Maxwell's equations. Fresnel's relations and Snell's law are, strictly speaking, not valid anymore. We explain via simple physical models the effects occurring at non-horizontal interfaces between different materials. At such interfaces, evanescent fields occur and modify the still well defined complex reflectivities for sand p-polarization. When the field vector projected on the sample surface is neither parallel nor perpendicular to the interface, the fields for sand p-polarization couple and cross-polarization arises from the different spatial behavior of the evanescent fields.

Human Vision and Electronic Imaging XIV, 2009

The appearance of objects in scenes is determined by their shape, material properties and by the light field, and, in contradistinction, the appearance of those objects provides us with cues about the shape, material properties and light field. The latter so-called inverse problem is underdetermined and therefore suffers from interesting ambiguities. Therefore, interactions in the perception of shape, material, and luminous environment are bound to occur.

2002

Rangeland Ecology & Management, 2008

Productive ground cover (PGC) is often used as a measure of sward health and persistence. To measure PGC, a camera stand was constructed to provide diffuse lighting of grass swards for color digital photography; the photographs were classified into productive and nonproductive cover using Mahalanobis distance. The PGC measurement techniques were tested on a grazing experiment that used four forage types: Lakota prairie grass (Bromus catharticus Vahl.), Kentucky 31 endophyte (Neotyphodium coenophialum)-free tall fescue (Lolium arundinaceum [Schreb.] S. J. Darbyshire), Kentucky 31 endophyteinfected tall fescue, and Quantum (novel-endophyte) tall fescue. The accuracy of the PGC maps was assessed using a stratified subsample of 48 images, 12 from each of four productive cover classes (0%-39%, 40%-59%, 60%-79%, and 80%-100%). On each of these 48 images 100 random points were labeled by a single skilled interpreter. The PGC percentages thus derived had an 83.7% agreement with the PGC maps. However, the percentages derived from the PGC maps were not well correlated with the PGC percentages derived from either ocular estimation (r 5 0.22) or a simple digital point quadrat method (r 5 0.47). This experiment highlights the potential for semiautomated classification of ground-based digital photographs for estimating PGC, though further research (including more direct comparison with established field techniques) is warranted. Resumen La cobertura basal (productiva PGC) a menudo es usada para medir la persistencia y salud de la pradera. Para medir la PGC se construyó un soporte para cámara para proveer una iluminación difusa de praderas de zacates para fotografías digitales a color. Las fotografías se clasificaron en cobertura productiva y no productiva usando la distancia de Mahalanobis. Las te´cnicas de cobertura basal productiva fueron probadas en un experimento de apacentamiento que uso cuatro tipos de forrajes: ''Lakota prairie grass'' (Bromus catharticus Vahl.), ''Tall fescue Kentucky 31'' (Lolium arundinaceum [Schreb.] S. J. Darbyshire) no endofito (Neotyphodium coenophialum), ''Tall fescue Kentucky 31'' endofito y ''Tall fescue'' Quantum (novel-endofito). La precisión de los mapas de PGC fue evaluada usando una submuestra estratificada de 48 imágenes, 12 de cada una de las cuatro clases de cobertura productiva clases (0%-39%, 40%-59%, 60%-79%, y 80%-100%). En cada una de las 48 imágenes un interpretador entrenado etiqueto aleatoriamente 100 puntos. Los porcentajes de PGC derivados de las imágenes tuvieron una concordancia de 83.7% con los mapas, sin embargo, los porcentajes derivados de los mapas de PGC no estuvieron bien correlacionados con los porcentajes de PGC derivados por estimación ocular (r 5 0.22) o por el me´todo de cuadrante simple de puntos digitales (r 5 0.47). Este experimento resalta el potencial de la clasificación semi-automatizada de las fotografías digitales terrestres para estimar la PGC, aunque se requiere mas investigación (incluyendo una comparación más directa con las te´cnicas de campo establecidas).

The …, 2009

The Photogrammetric Record, 1997

The XVIIIth International Congress of Photogrammetry and Remote Sensing was held in the

2006 Portland, Oregon, July 9-12, 2006, 2006

Machine vision is widely applied in automated inspection and monitoring systems. One of the most important components of machine vision systems is illumination. To remove and avoid halation on images, indirect lighting devices such as diffusers or domes with several lamps have been studied for post-harvest operations. However, it is difficult to control natural illumination in the field, because sunlight constitutes a point source, which causes shiny and shady parts on objects, and its intensity fluctuates with time. In addition, most parts of plants have a cuticular layer, causing halation effects, which reduce image quality.