The bi-directional cross track scanning

attitude fluctuation and the ETM sensor itself of Landsat7 result in the geometrical distortions including underscan

overscan and misalignment

which make geometric calibration more difficult than other kinds of model. The complicated imaging model increase the difficulty of geometric calibration as well. After the geometric model of imaging is studied

and the factors influencing imaging are analyzed

the systematically geometric calibration algorithms are derived

including generation and projection of line of sight

combination of attitude

generation of correction grid

finding corresponding input grid cell for a given output space

resampling

and so on. The model of line of sight are built in detail. Especially

the gap interpolation and detector delay are considered

and simplified methods are introduced to settle them. Finally

three parameters are introduced to evaluate the result of geometric calibration

including location precision

distortion and correlation between two lines. Experimental results show that the algorithms lead to good location precision

small distortion and good correlation between lines which all reach the requirement of the systematically geometric calibration

so validate the algorithms.