In this paper, the definitions of the space and projection systems, used in the mathematical model, have been shown. The projection system, situation of the plane and the projection centre have been established. The concept of the model of perspective projection process has been described: the stages of the geometrical data process (3D objects included in Electronic Navigation Chart- ENC) realized during projection process. Separately were considered the issues of changing of the reference plane and the projection centre with respect to the geocentrical reference system and movement of the ship as the geometrical object containing the reference system. They constitute a basis for preparing the conception of connecting the moving ship with the observer reference system using three established, nonlinear points (with known position with respect to the geocentrical reference system) placed on ship's board and with the horizontal topocentric reference system.