Remote Sensing - a tool for environmental observation

Landsat tm spot and noaa avhrr images were analysed

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usefulness of remote sensing as a tool for water quality control. Landsat TM, SPOT and NOAA- AVHRR images were analysed. It was shown that these sensors could detect spatial patterns of suspended matter and chlorophyll. Problems were identified with the high temporal dynamics of the surface water systems. NOAA-AVHRR can potentially provide an image every day but its spatial resolution is too small to detect the patterns of pollutants accurately. Landsat and SPOT only acquire an image every 16 days (if cloud cover does not prevent image registration), which is not sufficient to monitor highly dynamic systems such as surface water quality. A detailed project description is available in Buiteveld (1988). Airborne DAIS7915 Experiments in the Peyne area, France. The Department of Physical Geography is since 1997 involved in investigating the use of airborne imaging spectroscopy for environmental mapping. We determine the possibilities of mineral mapping in this study area using spectroscopic techniques, the possibilities of assessing
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97 canopy structural and chemical properties such as biomass and chlorophyll contents. Graduate and under graduate students are involved in these projects. Figure 6.8 Suspended matter in the IJssel lake in the central Netherlands.
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98 Chapter 7 Remote Sensing and Geographical Information Systems 7.1 Introduction For many environmentalists remote sensing is a tool to collect information on the natural conditions of vegetation or soils in their study area. Consequently, the classified remote sensing image is for them not a final product. The airborne or space born digital images must be com- bined with other sources of information or serve as an input for hydrological models, erosion models for bird or animal migration. Other sources of information comprise spatial (soil maps, vegetation maps, digital elevation models, hydrological networks, roads, administrative boundaries) and non-spatial information or databases (e.g. climate data). 7.2 Data Integration Issues A GIS or Geographical Information System is a computer system to store, process and display spatial and non-spatial information. As remote sensing images are already available in digital format, it is very easy to combine remote sensing data with data stored in a GIS. Figure 7.1 shows the principle of an integrated database containing remote sensing images, GIS maps and non-spatial information). The combination of images or maps from different sources requires an accurate geometric match. Consequently, geometric corrections are often necessary before the data can be integrated. Apart from geometric distortions the two images or maps may have a different pixel size. Resampling procedures can be helpful to overcome these problems. Resampling algorithms may work reasonable well for continuous data e.g. reflectance values, elevation information or groundwater levels. It is much more difficult to compute new pixel values for classified maps.
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