02 Contents Frame
MODELLING Types of models
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40 2019 ND-CP 413905
- Điều hướng trang này:
- Distributed point data including questionnaire-based surveys
| MODELLING
Types of models There is a range of methodologies for environmental modelling. Some of these are based on an assessment of factors and combinations of factors, and others primarily on a process modelling approach. All of these methods require calibration and validation, although the type of validation needed is different for each category. There are also differences in the extent to which the methods identify and approach the environmental problem: it may be in terms of estimating the ongoing process or in terms of risks of future occurrence of an event, under present climate and land use, or under scenarios of global change. A separate section below deals with risk assessment. Distributed point data including questionnaire-based surveys One important form of assessment is based on direct field observations. Data may be collected from regional experts in the subject matter. They may also be interpreted from field or air photo surveys of detectable features. Higher- resolution satellites (e.g. IKONOS) may allow this method to be applied using satellite images. Some quantitative data are usually available from test sites. These methods require validation to standardize differences in the intensity of study of different areas and in the clarity of suitable features on different images and in different environments. There are also differences in methods and traditions between scientists in different areas of the world. These methods by themselves cannot provide a complete picture except for small sample areas, and require the use of other methods to interpolate between the areas. The main advantage of distributed observations is that data are unambiguous where they exist, and give a good indication of the current state of the environmental problem, Annex 3 – Tools for land evaluation 91 while other methods lack this certainty. The main disadvantage of these methods is that they provide little or no information about when the event occurred, unless there are supporting data on this point. Many areas are thought to have been degraded by human activities since early classical times. Although of historical interest, this has little bearing on current or prospective erosion hazards. tải về 0.57 Mb. Chia sẻ với bạn bè của bạn:
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