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This paper approaches the problem of weed mapping for precision agriculture, using imagery provided by Unmanned Aerial Vehicles (UAVs) from sunflower and maize crops. Precision agriculture referred to weed control is mainly based on the design of early post-emergence site-specific control treatments according to weed coverage, where one of the most important challenges is the spectral similarity of crop and weed pixels in early growth stages. Our work tackles this problem in the context of object-based image analysis (OBIA) by means of supervised machine learning methods combined with pattern and feature selection techniques, devising a strategy for alleviating the user intervention in the system while not compromising the accuracy. This work firstly proposes a method for choosing a set of training patterns via clustering techniques so as to consider a representative set of the whole field data spectrum for the classification method. Furthermore, a feature selection method is used to obtain the best discriminating features from a set of several statistics and measures of different nature. Results from this research show that the proposed method for pattern selection is suitable and leads to the construction of robust sets of data. The exploitation of different statistical, spatial and texture metrics represents a new avenue with huge potential for between and within crop-row weed mapping via UAV-imagery and shows good synergy when complemented with OBIA. Finally, there are some measures (specially those linked to vegetation indexes) that are of great influence for weed mapping in both sunflower and maize crops. [ABSTRACT FROM AUTHOR]

Abstract: The eFieldBook program is a geology teaching tool with high didactic potential that guides a student’s work in the field using multimedia and other resources. This program allows the collection of geo-referenced geological information as well as its storage and transmission, if necessary, as soon as it is collected. The data can be collected as in traditional field notebooks or on maps and photographs. The information can be used as soon as it is collected and can be exported to other programs such as Word, Excel, Georient or statistical packages. eFieldBook safely stores and backs up user information by sending any data collected to a selected Internet target at regular time intervals. [Copyright &y& Elsevier]