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Measuring visibility using digital photography
Xingsheng Xie,Shanchang Tao,Xiuji Zhou
Chinese Science Bulletin , 1999, DOI: 10.1007/BF02886142
Abstract: An automatic digital photography visibility system (DPVS) is presented, which can directly measure and monitor horizontal visibility during daytime through digital shooting. After shooting a scene of given black object and background via its CCD digital camera, the system can capture and transfer photographic images in the camera to a computer, as well as process the digital images and calculate the value of visibility. The formulas for calculating visibility with this method and analysing the effect of non-black object on measured results have also been derived. And then the comparison of DPVS observations with a Lidar-visibility measurements has been carried out. The results show that the average deviation and relative average deviation of visibility acquired by DPVS from lidar-visibility measurements are respectively within 0.927 km and 6.68%.
Measuring visibility using digital photography

Xingsheng Xie,Shanchang Tao,Xiuji Zhou,

科学通报(英文版) , 1999,
Abstract: An automatic digital photography visibility system (DPVS) is presented, which can directly measure and monitor horizontal visibility during daytime through digital shooting. After shooting a scene of given black object and background via its CCD digital camera, the system can capture and transfer photographic images in the camera to a computer, as well as process the digital images and calculate the value of visibility. The formulas for calculating visibility with this method and analysing the effect of non-black object on measured results have also been derived. And then the comparison of DPVS observations with a Lidar-visibility measurements has been carried out. The results show that the average deviation and relative average deviation of visibility acquired by DPVS from lidar-visibility measurements are respectively within 0.927 km and 6.68%.
A geometric information on roughness of rock fractures based on image processing
一种基于图像处理的岩石裂隙粗糙度几何信息算法

WANG Wei-xing,YANG Ji-ming,
王卫星
,杨记明

重庆邮电大学学报(自然科学版) , 2010,
Abstract: This paper presents a method for measuring roughness of rock fractures based on digital image processing technique. Four self-defining geometirc characteristic parameters such as the difference between the wave crest and the trough of the rock curve, the number of corner points, the number of intersection points and the width between the rock curve and the fitting straight line were got under the VC platform. The joint roughness coefficients were analyzed and quantized by geometirc characteristic parameters. By analyzing and comparing the data from experiments, we find that there are obvious relations between these four parameters and roughness coefficient, showing that the new method is simple and feasible.
Evaluation of Digital Hemispherical Photography and Plant Canopy Analyzer for Measuring Vegetation Area Index of Orange Orchards  [PDF]
S. Khabba,B. Duchemin,R. Hadria,S. Er-Raki
Journal of Agronomy , 2009,
Abstract: This study presents the results of an evaluation of two indirect methods (Plant Canopy Analyzer (PCA) and hemispherical photographs) for measuring Vegetation Area Index (VAI) of two orange orchards, differing by their ground fraction cover (fc). The evaluation is based on reference data obtained by destructive measurements on limited samples, which allow to calibrate and validate an exponential relationship between the diameter of branches and associated areas of leaves (R2 = 0.99). The obtained results show that the two indirect methods underestimate the reference values of VAI. For the PCA device, the best estimates of VAI are obtained using the five rings for high fc (fc = 0.7) and using only four rings for low fc (fc = 0.3). For both case, the hemispherical photographs give accurate estimates of VAI: the relative errors are about 11 and 14% for high and low fc, respectively. Alternatively, a simple method consisting of calculating VAI as the weighted average of the maximum (VAImax, below the tree) and minimum (VAImin, at the center of four trees) values using fc as a weighting factor, was successfully tested (R2 = 0.90). For both indirect methods, the tree volumes are well estimated with comparison to the values calculated assuming an ellipsoidal form.
Effect of Partially Coherent Light on the Contrast of Speckle Patterns Obtained Using Digital Image Processing of Speckle Photography  [PDF]
Nasser A. Moustafa, Mohamad M. El-Nicklawy, Amin F. Hassan, Amany K. Ibrahim
Optics and Photonics Journal (OPJ) , 2013, DOI: 10.4236/opj.2013.35050
Abstract:

The paper is devoted to study theoretically, the effects of some parameters on the visibility of the speckle patterns. For this propose, a theoretical model for a periodic rough surface was considered. Using this theoretical model, the effects of grain height, its density, the band width and spectral distribution of the line profile (Gaussian and Lorentzian) illuminating a rough surface on the visibility of speckle pattern are investigated. An experimental setup was constructed to study the effect of surface roughness and coherence of the illuminating light beam on the contrast of speckle pattern. The general behavior of the experimental results, which agree with published data, is compatible with the new theoretical model.

Basic digital photography in dermatology  [cached]
Kaliyadan Feroze,Manoj Jayasree,Venkitakrishnan S,Dharmaratnam A
Indian Journal of Dermatology, Venereology and Leprology , 2008,
Abstract: Digital photography has virtually replaced conventional film photography as far as clinical imaging is concerned. Though most dermatologists are familiar with digital cameras, there is room for improvement in the quality of clinical images. We aim to give an overview of the basics of digital photography in relation to dermatology, which would be useful to a dermatologist in his or her future clinical practice.
Digital hemispherical photography for estimating forest canopy properties: current controversies and opportunities  [cached]
Chianucci F,Cutini A
iForest : Biogeosciences and Forestry , 2012, DOI: 10.3832/ifor0775-005
Abstract: Hemispherical photography has been used since the 1960s in forest ecology. Nevertheless, specific constraints related to film cameras have progressively prevented widespread adoption of this photographic method. Advances in digital photographic technology hold great promise to overcome the major drawbacks of hemispherical photography, particularly regarding field techniques and image processing aspects. This contribution is aimed to: (i) provide a basic foreground of digital hemispherical photography; (ii) illustrate the major strengths and weakness of the method; (iii) provide an reliable protocol for image acquisition and analysis, to get the most out of using hemispherical photography for canopy properties extraction.
Evaluation of digital photography as a tool for field monitoring in potentially inhospitable environments
J.A. Gilbert,K.R. Butt
Mires and Peat , 2009,
Abstract: Efficient and accurate vegetation monitoring is essential for successful assessment of upland moorland restoration. Working conditions on open moorland may be difficult, and surveying and monitoring of vegetation problematic. Image capture by digital photography, with subsequent computer analysis, was used to monitor Calluna vulgaris post-wildfire. Problems, for example picture warp, associated with close range photography of quadrats, were overcome. Digital imagery measurements of vegetation cover showed no significant difference compared with a traditional point quadrat method.
Digital Dermatoscopy Method for Human Skin Roughness Analysis  [PDF]
Suprijanto,V. Nadhira,Dyah A. Lestari,E. Juliastuti
ITB Journal of Information and Communication Technology , 2011, DOI: 10.5614/itbj.ict.2011.5.1.4
Abstract: In this study we propose a digital dermatoscopy method to measure the human skin roughness. By using this method we eliminate the use of silicon replica. Digital dermatoscopy consists of handheld digital microscope, image processing and information extraction of skin roughness level. To reduce the noise due to the variation of reflection factor on the skin we use median filter. Hence, by Fourier transform the skin texture is imaged in terms of 2D frequency-spatial distribution. Skin roughness is determined from its entropy, where the roughness level is proportional to the entropy. Three types of experiment have been performed by evaluating: (i) the skin replicas; (ii) young and elderly skin; and (iii) seven volunteers treated by anti wrinkle cosmetic in three weeks period. We find that for the first and second experiment that our system did manage to quantify the roughness, while on the third experiment, six of seven volunteers, the roughness are succeeded to identify.
Adaptive Aperture Defocused Digital Speckle Photography  [PDF]
Jose M. Diazdelacruz
Physics , 2005, DOI: 10.1364/AO.46.006105
Abstract: Speckle photography can be used to monitor deformations of solid surfaces. The measuring characteristics, such as range or lateral resolution depend heavily on the optical recording and illumination set-up. This paper shows how, by the addition of two suitably perforated masks, the optical aperture of the system may vary from point to point, accordingly adapting the range and resolution to local requirements. Furthermore, by illuminating narrow areas, speckle size can be chosen independently from the optical aperture, thus lifting an important constraint on its choice. The new technique in described within the framework of digital defocused speckle photography under normal collimated illumination. Mutually limiting relations between range of measurement and spatial frequency resolution turn up both locally and when the whole surface under study is considered. They are deduced and discussed in detail.
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