This paper examines the construction of the coordination contour around the stations of the conventional fixed service operating in the same frequency bands with the mobile Earth stations located on board vessels (ESVs). A new method for the realistic calculation of the coordination area is presented. This method takes into account the mobility parameters of the interfering stations such as their velocity and their frequency of passage from specific locations around the FS station and the specific interference conditions. Simulations in real interference environments prove its validity. Useful results for the coordination procedure between the two services are extracted and thoroughly discussed