Remote Sensing and Geographic Information System

emote sensing and geographic information systems can be defined as follows: "Remote sensing is any method of obtaining and recording information from a distance. The most common sensor is the camera; cameras are used in aircraft, satellites, and space probes to collect information and transmit it back to Earth (often by radio). The resulting photographs provide a variety of information, including archeological evidence and weather data. The images are also used in map-making. Microwave sensors use radar signals that penetrate cloud. Infrared sensors measure temperature differences over an area. Computers process data from sensors." ("remote sensing" World Encyclopedia. Philip's, 2005. Oxford Reference Online. Oxford University Press. Charles Darwin University. 12 September 2005 ). "Geographic (Geographical) Information Systems (GIS), GIS are integrated, spatial, data-handling programmes which will collect, store, and retrieve spatial data from the real world. They are powerful tools in decision-making, as they can incorporate co-ordinated data. It should be noted, however, that GIS only contain selected data; solely the properties which investigators have considered relevant, so that many variables will not be fed into the systems." "Geographic (Geographical) Information Systems" A Dictionary of Geography. Susan Mayhew. (Oxford University Press, 2004. Oxford Reference Online. Oxford University Press. Charles Darwin University. 12 September 2005 ) The relationship between remote sensing and GIS is that remotely sensed data is one of the input datasets in GIS. GIS can have other input datasets such as population data, species data, climate data etc. "GIS has the ability to analyse these input datasets in a spatial context and produce a conclusion which the operator of the system can interpret and use to help develop a solution to the problem being investigated." (http://erg.usgs.gov/isb/pubs/gis_poster)

The differences in remote sensing and GIS can be discovered in the data storage format and information processing focus of the data. Remote sensing will first be discussed first. The data collected in remote sensing is in the form of a raster image. The data in the images are implicit in georeferencing. This means that the spatial addresses of individual elements are determined by the ordering of the element in the data structure. The data does not have an inherent topology. This is where the grouping of elements into structural units is not inherently done. The data structure is simplistic - regular Cartesian grid. GIS data on the other hand is often, but not always, stored in vector format. The data collected in GIS is explicit georeferencing. This means that the spatial position of elements is a make up of part of the definition. The topology of the data is specified with each element. The data structures are more complex than raster format data. Remote sensing and raster processing are analysis oriented. Continuous spatial overlap, proximity etc. and ``landscape'' wide statistics are easily calculated. Spatial analysis is simpler in raster form. GIS and vector processing are usually database management oriented. Analysis of network inter-relationships, that involve topological elements, is more natural in vector form. Element length, area, perimeter etc. are explicitly defined (this is hard to do in raster systems!)

In a modern GIS workflow, data moves from its original sources to government agencies,

inspectors, design firms, environmental consulting firms, construction firms, facility

managers, and so forth. At each step, the data may be converted from one format to

another and is often printed, handed off, and subsequently entirely re-entered. Data

conversion