Automated Extraction of Morphologic and Hydrologic Properties for River Njoro Catchment in Eastern Mau, Kenya

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Olang, L. O.
Kundu, P.M.
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AGSE Publishing
During the past decade digital collection of geodata has become a common subject for the public. Due to the free availability of the GPS signal with selected availability off since May 2000, everybody on Earth is able to determine the actual geo-position within an accuracy radius of about ten meters. GPS is under revision and the new generation of satellites is currently installed in the orbit. This will provide a higher reliability and more precise position accuracy. In addition new and competitive global positioning systems have and will become available, e.g. the Chinese COMPASS, Russian GLONASS and finally the European GALILEO. The next decade will bring a series of new receivers and those will make advantage of all available GPS signal in combination. The public, professional geodetic services and especially the mapping community will truly benefit from these developments and open map services like Open Street Map (OSM) will provide increased geo-precision. Optical satellite remote sensing images are another important source for the acquisition of geoinformation. For the mapping of urban objects, a fine spatial resolution is necessary providing enough detail for reliable object recognition. A series of new spaceborne sensors have been launched recently, those collect image data with a spatial resolution up to 0.41 m in the panchromatic (pan) band. This spatial resolution can be compared with the detail-accuracy offered by classical aerial photos. However, some more advanced features are pushing the satellite images in the first position compared to aerials: spectral bands are not limited to three colors only, the radiometric capabilities exceed the image quality of aerial by far and finally the revisit period of these satellite sensors is in the range of about three days. [The price of the satellite images (per area unit) might be reduced compared to aerials but it will not be considered here.] Having all these criteria in mind we can state that a new generation of remote sensing information source has become available, a true substitute for the classical aerial photos. These two substantial new developments, combined GPS signals, 2nd generation, and super high resolution satellite remote sensing, will facilitate the precise mapping of urban areas substantially. On the one hand unplanned urban settlement regions with a highly diverse, inhomogeneous structure are difficult to survey, on the other hand especially these region need to be mapped first, because an infrastructure network has to be established. Infrastructure in these cases means: freshwater supply and wastewater drainage, electricity grid and a telecommunication network. The Kibera informal settlement in Nairobi, Kenia, is one of the rapidly changing suburban regions with a highly diverse, unmanaged -and in some areas unknown- structure. “Map Kibera” is the name of a mapping project especially for this slum, and Map Kibera may definitely benefit from the new developments of geodata acquisition..
GPS,, Satellite Imagery