Oc78 Unit 3: Remote Sensing Have you ever wondered how we can know all kinds of things about the Earths surface from an image taken by a satellite orbiting many hundreds of kilometres above us? Remote Sensing Definition: a science of deriving information about the Earth`s surface (planet or object of interest as well) from images acquired at a distance Analogy: trying to determine the type of animal by its footprints Objective: to understand how resolution, spatial and spectral, effects feature identification. Spatial Resolution: typically pixels may correspond to square areas on the ground ranging in size from <1 to >1, 000 square metres. Smaller the resolution, more visibility (of smaller objects). Raster image: grid where every pixel is a coordinate on the grid. Spectral Resolution: The number of different wavelength bands recorded usually equivalent to the number of sensors carried by the satellite. (More than just colours and shades, UV radiation etc.) Air photos.Special case Vertical air photos stereo pairs (stereogram) Satellite images Scale S = fH where f=focal length and H=height of camera Image Understanding What form of radiation? How was the radiation gathered? What is the scale? What is the resolution (square metres per pixel)? Are patterns related to things not visible? What errors are present? When was the image acquired? Wavelengths Length determined by distance between each wave.