USING GIS TECHNOLOGIES IN PROCESSING AND INTERPRETATION OF SATELLITE IMAGES PUBLISHEDM. HERBEI, L. DRAGOMIR, C. Popescu, Silvica ONCIA
The Geographic Information System is a collection of located, collected, stored and managedgeographic data with the use of the computer, data which can be used to perform various spatialanalyses. The special GIS operations over the spatial information make from these instruments more thanjust efficacy instruments for making maps, but especially, irreplaceable instruments for analyzing theinformation that refer to the terrestrial surfaces. GIS maps must be made exploiting all availableresources based on rigorous analysis of their content and the costs involved, seeking assurance requiredwith maximum efficiency. Each data source requires the existence of specialized programs that wouldbring appropriate map data into digital form, starting with providing necessary equipment, going throughtechnological problems and data conversion, with the purpose of preparation and proper training ofpersonnel. In a GIS, data can be stored in two fundamental spatial data models: vector and raster. Rawraster data can be as follows: satellite images or orthophotos, while the raw vector data can be obtainedfrom topographic survey or data acquired by GPS technology. The information obtained from remotesensing is contained by the cosmic or aerial images, which can be interpreted for many purposes.Building these images is based on detection and registering of electromagnetic energy reflected or issuedby the surface of the objects present on the visual field of the sensors, which interacted with theelectromagnetic energy issued by a natural source (e.g. Sun, Moon) or an artificial one (e.g. radar). Theresponse of the objects from nature to various wavelengths of electromagnetic radiation is different,depending on their physical and chemical properties, configuration and surface roughness, itsillumination intensity and angle of incidence. These responses recorded via sensors translate the imageby the emergence of patterns (features), based on which objects can be distinguished and identified. Theremote sensing data is public, meaning it can be acquired from any area of the world and by anyone, withsome restriction.
GIS, Landsat, bands, combination, band math