Gis Spatial Data Midline Element Uncertainty And Visualization

Data is the most basic and important component of geographical information system (GIS),also it is the largest part of the proportion of the investment in the GIS.Researching data uncertainties is of great significance for the accuracy analysis and quality control of GIS data,and it is the guarantee for GIS's survival and development and the premise to decision-making for various plans and management analysis in socio-economic activities. Many scholars have done a great deal of work in the position accuracy analysis and have achieved some fruits,which mainly touches upon the digital error analysis,the graphics elements geometric correction,and the line element uncertainty model analysis for GIS data;but they haven't do deep enough works for the model visualization.Along with "Digital Earth","Digital City" bringing forward,which needs digital description for the earth geospatial,there is an urgent need to research visualization for geospatial data uncertainties.There are many input-data sources for GIS spatial database;and data uncertainties include random error,systematic error,measurable and non-measurable error,numerical and conceptual errors.Point,line and area are basic elements in GIS vector spatial data. Therefore,the main point of researching GIS spatial data uncertainties is the positioning uncertainty for point element,line element,and area element.This paper has summarized the basic theory for GIS spatial position data uncertainty estimation and the error propagation,and practical estimation methods.Also this paper has researched line element's "ε- belt ","E- belt ","G-belt","ε_σ- belt " model and the error model expressed by error in point measurement;and then the writer has deduced a way that is to make a derivation after rotating plane line element "G-belt" error model translation and then computing conversely with the result to parse "G-belt" boundary line.This way is based on a rigorous theory and is more convenient to improve visualization effect. According to the theory of "ε_σ- belt" model and the error model expressed by error in point measurement,this paper has still detruded their boundary line analytic formula.This paper also has brought forward a new circular curve error belt model-- circular curve error model expressed by error in point measurement by quoting error belt model expressed by error in point measurement to circular curve.With a view to the characteristic of the improved "G-belt","ε_σ- belt",line and circular curve error belt,the writer has compiled related programs with MATLAB program language,and attained perfect visualization effect.