This paper introduces on several problems about projective calculation of base length in control survey for the purpose of increasing the accuracy of the measurement.

Calculating the image-space coordinates of the ground points,which can be also called back project calculation,is the basis for the processing and applications of linear array pushbroom imageries,such as the stereoscopic mapping,incorrect image geometric rectification and so on.

In this paper,the axial section profile of worm with straight generatrix is analyzed and calculated according to angle projection calculating.