Working on new equipments to increase agricultural productivity and safety, reducing human action hardness , Cemagref and Lasmea have developed an help guidance system for agricultural vehicles. The aim of this system is to help the operator to guide the machine in order to give more attention to the order task. To r each this goal, we use a visual perception of the environment because this sensor gives a solution well adapted to lots of situations. This project began with researches on a visual guidance system for a lawn mower in 1990 and has been adaptated to the development of the same system for a combine harvester in 1995. We model the lawn mower with a virtual axle, use trajectory generation to guide it, and localize the vehicle at each iteration to insure the servoing task. For the combine harvester, we decide to use the task function approach 23] and then to control the combine harvester directly in the sensor space.