There is a great application potential for the fusion of remote sensing images. With the development of quantitative remote sensing

not only improving spatial details but also preserving the spectral information of multispectral bands were required. The principle and methods of two fusion algorithms

SFIM (smoothing filter-based intensity modulation) and Gram-Schmidt (Gram-Schmidt transform)

were described. In a case of IKONOS image in city

visual judgment

quantitative statistical parameters and graphs comparison were used to assess these two algorithms

which were also compared to the traditional methods of IHS transform and PC(principal component) transform. The results showed there was no distinct difference in spatial details improved. However in terms of spectral information fidelity

both IHS and PC method were the worst

Gram-Schmidt method was better

while SFIM method was the best.