Multi-sensors remote sensing satellite imagery are merged to improve resolution of imagery by use of methods and algorithms for decision making for real world. Image Fusion techniques are band selection method, colour related techniques, statistical numerical methods, principal component analysis, high pass filtering, regression variable substitution, canonical variant substitution, component substitution and wavelets. Image fusion purpose is selection of appropriate techniques and algorithms for image merging and sharpening, accuracy in registration, feature enhancements, image classification, change detection, stereo modelling and so on. Image fusion major application areas are as topographic mapping and map updating, land use land cover mapping, agriculture and forestry, flood monitoring, ice sheet and snow monitoring as well as geology and geomorphic processes and exploration of earth’s resources for regional development.