Abstract: A convergence algorithm of field stitching and intersection measurement is proposed based on the development of two prototypes of high-speed video-measuring systems with external field stitching. Five coordinates are established for the earth centroid and optoelectronical systems. The definations of the coordinates are introduced and coordinate transforms are discussed. The experiment of intersection measurement and field stitching for an identical moving target is carried out with the data from eight cameras in two high-speed TV measuring instruments. The result shows that the stitching algorithm is correct and effective, and has obtained an unique solution. Meanwhile, the influences of earth curvature and meridional convergent errors are fully correated, which indicates that the intersection measurement algorithm can also be used in the intersection measurement of other optoelectronical measurement and control instruments.