An analysis of influence on nonnavigable shallow areas using different methods to interpolate depths

Currently, various water depth interpolation methods used to construct nonnavigable shallow areas are simply and indiscriminatingly used without taking their respective adaptabilities into consideration. Firstly, three typical methods used to estimate a water depth at an arbitrary position on a chart are summarized as follows: (1) estimating the depth with the shallowest depth of the three vertexes of a triangle; (2) estimating the depth with linearly interpolated by the depths of the three vertexes of a triangle; (3) estimating the depth with linearly interpolated by the depths of the three vertexes of a triangle as well as the node depths of isobaths. Correspondingly, three methods, namely is shallowest interpolation method, linear interpolation method, and additional interpolation method, are proposed for constructing nonnavigable shallow areas based on three aforementioned different ideas. Finally, the adaptability of the three different interpolation methods used to construct nonnavigable shallow areas is analyzed. The experimental results demonstrate that (1) the shallowest interpolation method can ensure the navigation safety better than the other two methods, and linear interpolation method is worse than the shallowest interpolation method, and the additional interpolation method is the worst. Besides, the shallowest interpolation method loses most utilizing rate of the navigable resource, and linear interpolation method is less than the shallowest interpolation method, and additional interpolation method is the least. (2) In the areas of the narrow straits or waterways on small-scale chart or medium-scale chart, both shallowest interpolation method and linear interpolation method may make some mistakes that some areas in the narrow straits or waterways are nonnavigable, whereas additional interpolation method can express nonnavigable shallow areas correctly.