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GIS and Remote Sensing are different tools, yet when used together can give a clear picture of what processes are happening on the earth’s surface.
A geographic information system (GIS) is the analysis of spatial data through a computer-based platform. It enables statistical analysis of geocoded, or georeferenced data and renders it in a way that can be visualised by the user to spot trends and patterns. Furthermore, a GIS allows a user to model and predict how a change in variable can alter the current status quo, for example a town planner may simulate increased car flow through a road network. GIS therefore helps policymakers to understand complex issues better and propose better solutions.
Remote sensing is a method that is used to create measurements of the earth system using a variety of platforms – including, but not limited to, airplanes and satellites. The data therefore does not require the user to be collecting the data in situ. These platforms collect data in images (for example storing reflectance values within a pixel). Remote sensing platforms are broadly split in two types – firstly passive sensors require external illumination of a target (eg solar radiation) or emittance from the target (eg thermal infrared from volcano) and then measure the reflectance from that target. Active sensors produce the illumination of the target that they are measuring.
Many remote sensing software packages also have specialised raster processing functionality, for example image pre-processing and pan-sharpening (increasing the spatial resolution of an image using a panchromatic image). However, in terms of raster analysis there is still benefit in moving pre-processed rasters across to a dedicated GIS platform.