Research Of Isoline Drawing With Faults Algorithm Based On Geoview System

Contour line graph is a kind of widely-used graphics, which goes through the points with the same value of a type of spatial distribution in a 2-dimensional plane. Contour line graph is the combination of data and graphics, which helps to reflect the trend of data change and make out the direct computer simulation results for skilled-engineers. As a kind of way of reflecting quantity change, Contour line graph, widely used in modern scientific research, is a kind of common-used and effective description method, especially in the earth science, engineering analysis, aided-decision and computing etc. Therefore, it is an important result expression in many fields, such as application in engineering analysis and computer field, terrain isoline in aerial measurement, isotherm in temperature field, equivalent stress strain field contour line in finite element analysis, as well as the application in weather report, geological measurement and geological analysis.Most of the strata we see today suffer from geological force influence for a long history, and geofracture happed to them under the tension, extrusion and rotation of geological force. Generally speaking, normal fault formed under tension force, and reverse fault under extrusion force. While fault study has its significance in the following areas: (1) mineral deposit formation, orebody occurrence and distribution, gas & oil resource exploration and evaluation; (2) big engineering projects like engineering architecture, irrigation works construction must have their fault geological materials in the local districts as reference for designers; (3) fault formation has close relationship with underground water transformation and reservation; (4) fault, particularly active fault is easy to result in earthquake activity; (5) fault has close relationship with geomorphic development.In our country's geological survey, because of the characters of multi-source, multi-quantity, multi-variety, multi-dimension, and multi-subject of resource exploration data, it needs specific solutions for mutual border lines (fault, geological border line etc.) and districts (stratum, rock body, metamorphic zone etc.) information under specific situation, which may (also should) exist in the same graph.Because of very complicated geological structure, mass data to be processed, and unbalanced data distribution, hence, it's one of important ways to raise data process efficiency in resource exploration, project construction, earthquake prediction and so on, by means of effective use of computer's data and graphics processing ability to draw contour lines with faults.About contour line drawing, predecessors did a lot of work, put forward of mature drawing algorithms, including contour point calculation and contour line trace, as well as abnormity control during trace processing. Additionally, there are many mature software systems in current market which can draw contour line, for example Surfer developed by Golden Software. However, these software cannot or cannot well deal with fault problem, this is the base of thesis.On the basis of the predecessors' work, this thesis raises the algorithm of contour line drawing with fault, particularly with normal faults. Chapter 1 mainly introduces the research purposes of isoline and with fault, as well as the current status both home and abroad, and we know its significance, and social and economic values. Chapter 2 discusses point data triangulation, which adopts the most common-used Delaunay triangulation. Delaunay triangulation is the most optimized triangulation, which can assure the addition of all the triangles' smallest inner angles the biggest one, that is, it will not form acute triangles. Therefore, during the tracing process, interpretation calculation errors can be greatly reduced. Subsequently, it introduces the research status of common-used constrained Delaunay triangulation algorithms, constraint diagram, division-merge algorithm, point inversion, SHELL triangulation, two-step algorithm etc. and compares their advantages and disadvantages. And it analyzes BS algorithm. It first requires Delaunay trianglulation for constrain points and gets a raw DTS, and then checks constrain line segments, subdivides it from the middle point, insert into DTS. At the end of this chapter, it describes polygon-border Delaunay triangulation. Firstly, it realizes T(P) triangulation, and then DT(P), gradually inserts points to form algorithm.Chapter 3 is the main topic of this thesis. In actual application, there is some Delaunay triangulation with islands. For this situation, here raises two methods, middle point insertion border cutting and sub-area division. Sub-area division has two steps. The first one is sub-area division and the second one is polygon-border Delaunay triangulation. About Delaunay triangulation with normal faults, this chapter puts forward of whole area and sub-area division Delaunay triangulation. The former first draws faults, and then creates triangles. The latter first divides the area into several sub-areas and do Delaunay triangulation on each sub-area. During the sub-area division, it introduces "over-constraint" and "Least squares method like". Lastly, the chapter introduces Delaunay triangulation with reverse faults, which also divides area into several parts and then merge the sub-area.Now we can go into contour line trace after triangulation. This thesis discusses contour line trace method based on triangulation network, and its labeling, smoothing, and filling. Finally, it simply introduces Geoview system and the contour line drawing with fault module design.In this thesis, there are three innovation points:1. For Delaunay triangulation with island, it puts forwards of assistant point selection method: store border points of the island into talbe anti clock-wise, choose one and calculate the distance to the border; and then one point or two points with the shortest distance is/are are the selected point(s) according to actual situation.2. It introduces "Over-Constraint" into isoline drawing with normal faults. Over-constraint means the constraint factors resulting from the non-existing hypothesis on the raw data for convenient treatment. 3. It raises "Least squares method like", which introduces border line in order to reduce the "Over-constraint" affection. It refers to "Least squares method", so called "Least squares method like".