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ADAPTIVE THRESHOLD FOR DROPLET SPOT ANALYSIS USING WATER-SENSITIVE PAPER
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2004
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Precision AgricultureEnvironmental MonitoringEngineeringAgricultural EconomicsPrecision Crop ProtectionDetection TechniqueImage AnalysisAgricultural Water ManagementBiostatisticsPublic HealthEdge DetectionAgricultural SprayersIrrigationWater QualityMedical Image ComputingAgricultural EngineeringWater ResourcesEnvironmental EngineeringBiomedical ImagingCrop ProtectionCoverage MeasurementRemote SensingAdaptive Threshold
A methodology has been developed for coverage measurement in agricultural sprayers using water-sensitivepaper and image analysis processing. The model is based on an adaptive threshold applied to 8-bit gray-scale imagesscanned at 2400 dpi. A collection of 22 samples with different coverage levels were selected and relationships were soughtbetween threshold and statistical image histogram parameters such as mean, mode, and median of gray levels. In addition,the samples were digitized with CAD software, and true droplet spot area was measured. Linear-regression analysis showedthat the descriptive statistics that best correlated to threshold corresponded to the mean gray level with an adjusted R2 of 0.91,and the mean relative error was 5.15% in the coverage measurement. This methodology can reduce operator subjectivity andautomate the process of analyzing samples of water-sensitive papers using any image analysis software.