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首页> 美国政府科技报告 >Evaluation of the Use of Remote-Sensing Data to Identify Crop Types and EstimateIrrigated Acreage, Uvalde and Medina Counties, Texas, 1989
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Evaluation of the Use of Remote-Sensing Data to Identify Crop Types and EstimateIrrigated Acreage, Uvalde and Medina Counties, Texas, 1989

机译：评估使用遥感数据识别作物类型和估算的灌溉面积，Uvalde和medina县，德克萨斯州，1989年

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摘要

Remote-sensing data were used to estimate that 190,000 acre-feet of water waspumped from the Edwards aquifer in 1989 to irrigate crops in Uvalde and Medina Counties. Landsat digital satellite images for March and July 1989 were combined and classified to identify the areas of crops irrigated with water from the Edwards aquifer in the two counties. Normalized difference, the difference between the infrared and red reflectance values divided by the total of those values, was used to discriminate vegetative from nonvegetative ground cover. The images subsequently were classified using maximum likelihood, an unsupervised classification procedure. Detailed vegetation distribution maps of two calibration sites in the study area, and boundaries of the areas probably irrigated in 1989, helped to interpret the results and to separate probable irrigated areas from the rest of the image. Results were verified using crop acreages reported by the U.S. Department of Agriculture. Irrigated-crop areas subsequently were multiplied by the respective duties of water to calculate the total quantity of water pumped from the aquifer for irrigation.

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