Navigation is the only way to develop and utilize marine resources, while the promotion of seafarers’
quality is the basic force of navigation, so navigation simulator plays an important role in modern navigation
education. The simulation research on the operation of the union purchase is important to improve the special
operation training of the actual cargo handling of the union purchase. On the basis of the Cartesian coordinate
system transformation algorithm, the algorithm model of the union purchase operation is constructed. On the
basis of three-dimensional (3D) rendering engine technology of open scene graph (OSG), the algorithm model
of finding the space coordinates of the cargo point is established. The model of catenary equation is used to
optimize the scene appearance of the cargo wire. By combination of QT channel signal mechanism and OSG, the
simulation interaction of the union purchase operating system is realized. By acquiring the 3D coordinate values
of each point, we fit the trajectories of each point in the operation and compare the trajectories. The results
show that the model has high interactivity and small error. The comparison of the states of the cargo wire before
and after optimization shows that the optimized wire is more realistic and the high fidelity meets the needs of
operational training and simulation systems.