Research On The Automatic Plotting Of Marine Environment Isoline

Over the past ten-odd years, the development of oceanographic technologies such as aerospace remote sensor, buoy, multi-beam echometer etc. serves to increase marine data collection in ocean field. Therefore, many problems that involve the storage, management, access, analysis and display of mass marine data are pressing for solution. GIS is already used in the ocean field as a effectual means of settling above problems. Isoline analysis plays an important role in GIS spatial analysis. At the same time, drawing the isolines automaticly by computer is the precondition and basis for realizing isoline analysis; also the key technique and one of the main parts of the visualization in marine environmental elements.This paper mainly discusses the algorithmic of tracking, building, smoothing, filling and labeling of isolines etc. Finally the application of isoline-plotting is described in the marine environment applitation system.Firstly, the compositions, data formats and visual expression of the marine environment information are studied. Secondly, based on the former work, the principle and different algorithms of isoline-plotting are researched; also the differences of different isoline-plotting methods are compared. Thus the Griding-method is adopted to build isolines from the regular grid data in this paper. Thirdly, for the features that low resolution of the original data, much sharp angles and roughness of isolines, the cubic Bspline algorithm is applied to generate glossy curve after analyzing the result of different smooth methods. Then for the filling problem of isolines, the existing isolines filling algorithm are analyzed and compared, and a programming idea of drawing and filling isolines respectively is proposed according to the layered characteristics of the data, moreover the zone filling is implemented by taking advantage of rapid raster display of OpenGL. This algorithm provides excellent visual effects comparable with commercial software. At last, a simple but useful vector judgement method of isoline labeling is applied to this system, and the labeling location is chosen, also the detailed process of labeling is discussed in this paper.The marine environment information isoline map has been testified to be understands easily, full-featured, high-quality. Isoline analyzing system that developed by the author has been integrated the elements requesting functional modularity of the marine environment applitation system and has been used in the applied project.