3S技术在水利工程中的应用-遥感.ppt

Spectral Signatures Band Placement Band Display Color Theory Multispectral Display AVRIS Hyperspectral Cube Sensing Pixels Each cell is called a “picture element”, or pixel Each pixel represents a single brightness value for a specific geographical area Sensor Properties Spatial resolution Spectral resolution/# bands Radiometric resolution Temporal resolution Spatial Resolution Measure of the smallest angular or linear separation between 2 objects that can be resolved by the sensor In practice, sensor system’s nominal spatial resolution is the dimension in meters (or feet) on the ground projected instantaneous field of view (IFOV) Generally, smaller spatial resolution ? greater the resolving power of the sensor system Spatial Resolution (cont.) Spatial Resolution Useful rule: To detect a feature, the spatial resolution of the sensor system should be less than ? the size of the feature measured in its smallest dimension. Spectral Resolution Number and size of the bands which can be recorded by the sensor – nominal spectral resolution Coarse – sensitive to large portion of ems contained in a small number of wide bands Fine – sensitive to same portion of ems but have many small bands Goal – finer spectral sampling to distinguish between scene objects and features More detailed information about how individual features reflect or emit em energy increase probability of finding unique characteristics that enable a feature to be distinguished from other features. Spectral Resolution the SPECTRAL resolution defines the range of light stored in the image A black and white photograph stores a visible light; it has one channel that stores the light for 0.4 to 0.7 micrometers A natural color image stores reflected red, blue and green light in different channels; e.g. 0.45 - 0.52 mm for blue, 0.52 - 0.60 mm for green and 0.63 - 0.69 mm for red A LANDSAT image contains 7 channnels as described above that store reflected light other than visible light. A HYPER-SPECTRAL imag