Urban Environmental Studies

Urban Landscapes

Urban landscapes are typically a complex combination of buildings, roads, parking lots, sidewalks, garden, cemetery, soil, water, and so on. Each of the urban component surfaces exhibits unique radiative, thermal, moisture, and aerodynamic properties and relates to its surrounding site environment to create the spatial complexity of ecological systems. To understand the dynamics of patterns and processes and their interactions in heterogeneous landscapes such as urban areas, one must be able to quantify accurately the spatial pattern of the landscape and its temporal changes. It is necessary to have a standardized method to define theses component surfaces and to detect and map them in repetitive and consistent ways.

Various approaches have been developed in the studies of landscapes in general and urban landscapes in particular in the fields of geography, planning, landscape ecology, natural resources, environmental science, and so on. The land use and land cover approach is a predominant one, especially in geography, planning, and landscape ecology. Land cover can be defined as the biophysical state of Earth's surface and immediate subsurface, including biota, soil, topography, surface water and groundwater, and human structures. In other words, it describes both natural and human-made landscapes of Earth's surface. Land use can be defined as the human use of the land. Land use involves both the manner in which the biophysical attributes of the land are manipulated and the purpose for which the land is used. However, the relationship between land use and land cover is not always direct and obvious. A single class of land cover may support multiple uses, while a single land use may involve the maintenance of several distinct land covers.

Urban areas are composed of a variety of materials, including different types of artificial materials (concrete, asphalt, metal, plastic, glasses, etc.), soils, rocks, minerals, and green and nonphoto-synthetic vegetation. Remote sensing technology has often been applied to map land use or land cover. Each type of land cover may possess unique surface properties (material); however, mapping land covers and materials have different requirements. Land cover mapping needs to consider characteristics in addition to those coming from the material. The surface structure (roughness) may influence the spectral response as much as the intraclass variability. Two different land covers, for example, asphalt roads and composite shingle/tar roofs, may have very similar materials (hydrocarbons) and thus are difficult to discern, although from a material perspective, these surfaces can be mapped accurately with hyperspectral remote sensing techniques. Therefore, land cover mapping requires taking into account the intraclass variability and spectral separability. On the other hand, analysis of land use classes would nearly be impossible with spectral information alone. Additional information, such as spatial, textural, and contextual information, is usually required for a successful land use classification in urban areas.

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