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Remote Sensing - a tool for environmental observation

Land use classes cannot be averaged and other methods

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Land use classes cannot be averaged, and other methods such as majority filters must be applied. A majority filter attaches the most occurring class in the input kernel to the output cell. 7.3 Modelling Spatial Processes in a GIS using Remote Sensing Data Models are used to represent complex processes such as erosion or evapotranspiration because the scientific knowledge is lacking to describe that process exactly. A model is a simplified representation of reality, which describes the object or the process in a formal, structured way. Models can help us to increase our understanding of the process: they offer the opportunity to explore scenarios and to assess the importance of each individual input variable. The use of remote sensing information as input to a model requires that: - The scale at which the model predicts the processes should match the scale of the images; - The time-scale of the model should match the acquisition frequency of the images; - It should be feasible to derive some of the model inputs from digital images.
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99 Figure 7.1 Integrated image processing and analysis by means of a GIS (Buiten & Clevers, 1993). The scale of the image and the model should match because it does not make sense to model erosion or transpiration processes at field size using images with pixels of 1 km². The same is true for the time-scale, some models are developed to forecast e.g. soil losses of single storm events. Remote sensing input requires models that give long-term, e.g. seasonal or annual values. Furthermore, it is important that the model is based on variables that can indeed be
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100 derived from remotely sensed images. Consequently, other conditions to be fulfilled by the model are: - It should be based on the concepts of the erosion process; - The model can simulate the effects of temporal changes in land use and land management; - The model should match the distributed character of remote sensing; - The model should be validated for a number of study areas under a range of natural conditions. Examples of modelling spatial processes in a GIS with input from remote sensing data can be found in De Jong (1994a), Nieuwenhuis (1993), Nieuwenhuis et al. (1985) and Menenti (1993, 1980).
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101 Information sources and important addresses: Kring voor Remote Sensing The ‘Kring’ is a Dutch organization for remote sensing, it provides news and information on remote sensing activities in its newsletters, it organizes symposia and excursions. Everybody interested in remote sensing can become a member (students are also welcome). Personal yearly membership is around Euro 25. The Kring has merged in 2004 into GIN: Geo-informatie Nederland and can be accessed at http://www.geo-info.nl/CMA/templates/HMhome.aspx KNMI: Koninklijk Nederlands Meteorologisch Instituut, De Bilt ( http://www.knmi.nl/ ).
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Land use classes cannot be averaged and other methods such...

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