A Study on Drawing Depth Contours Using Grids Based on Irregular Area, Arbitrary Direction and Different Scale in Bathymetric Survey for Port Engineering
Lihua Zhang · Port & Waterway Engineering · 2005
Grid contouring is one of methods often used for drawing depth contours by computers. Due to special demands of processing soundings, there might appear some problems, which are difficult to deal with by conventional methods, such as depth contour′s extending towards shallow side, irregular plotting area, arbitrary direction of depth grids, and different scale between horizontal and vertical grids. In this paper, a method that the following node should thread the side having a shallower depth is put forward to eliminate the ambiguity in tracing depth contours and avoid extension towards the shallow side; To counter the irregularity of plotting area, measures such as false node noting and double direction tracing are suggested;In consideration of arbitrary direction of depth grid and different scale, the corresponding methods based on rotary transformation and translation transformation are proposed. Theoretical analysis results and practical applications prove that the methods and measures provided in this paper are effective for solving the above-mentioned problems and can be used for drawing depth contours in bathymetric survey for harbor engineering.