The Method Of Automatic Contouring Mapping And Realization On Computer

The contour map is one of the most basic and common used graphicdocument to reflect the geological parameter and the developmentdynamic target plane distribution. In the theory, this paper has carried onthe careful study and the analysis to the contour map plan process,thoroughly researched the character of contour map as well as theproduction method, and discussed respectively the different two methodsof plotting contour map, namely: Rectangular method of lattice andtriangular net law.According to the primarily actual situation that Sa Pu oil layerdeposited by the fluvial facies in Daqing Oil Field, the special studyindicated that the grid interpolation was prone to descript and control thedeposit character of the fluvial facies, therefore, this paper used themethod of lattice to realize the contour map plan.The method of lattice plan mainly establishes the computation grid tocover the entire region through carrying on grid processing to the certainregion. The grid horizontal and longitudinal interval may be equal or not.And then the plane contour map automaticlly plotting will be realized aftergrid nodes interpolated and contour tracing.1. Grid division and grid nodes value computationWe must determine the number of grid line according to the actualproblem, and then various nodes will be interpolated. This softwaredevelopment uses two interpolation methods:(1)Counter-distance N power weighted mean methodThis method determine the contribution of the given parameter valueZ i to the unestimated parameter value Z* by the size of distance betweenthe given nodes and unestimated nodes Di on the plane.(2)Geological statistics methodThe geologic statistics method is a linear smooth interpolation method.It surpassed the weighted method of inverse ratio to distance inmathematics lying in that it not only considers the relationship betweenunestimated points position and the known data position, also the knownpoints position. This may strengthen the contribution of data configurationon the whole, and the use semivariogram function to quantify therelationship.2. Contour searchingAfter the complete contour points calculated, we m ust draw one linewith all of them by rule and orderly, which is called the contour tracingquestion, dividing into three steps of processing following:How to determine the trend of the contour line entering the grid: thereare four possible cases as following: From the top to bottom, from left toright, from bottom to top, from right to left. Among the other things, thetrend from bottow to top and from left to right may be distinguished by theserial number, while the other case by the contour relative coordinatesposition.How to determine the trend of the contour line going out the grid: Thecontour line may go out of the grid only in the other three direction,and ifnot controlled by orli ,it occurs that the contour line will cross and bedefinite. In the processing, we should determine the trend by the principleof considering the distance between the line and the present contour pointafter the original trend.When mesh nodes same to the contour points: Sometimes the meshnode elevation value and the intersection surface elevation value is equal,but at the same time the mesh node also is the common point of fourneighboring grids. The identical point is stored respectively in four differentunits, thus there will be some the repeated use and tracing chaoticlyquestions when tracing. Regarding this situation we must preprocess. Themethod is that adds on an enough small value to the mesh node to givethe revision. The choosen revision is so small that it will influencecartography precision, but also avoid the above questions.3. Contour line searchingDue to the several branches of contour lines under the identicalelevation value, if we want to differentiate them and map the integralcontour lines, a contour line searching method is necessary. The keyelement is how to search the initial point of one contour line and searchfrom the top to the end .Expatiate on the open curves and the closedcurves respectively.The Open curve searching: First search the bottom edge on therectangular boundary from left to right, whether there is the contour pointor not, if has, increases a hypothesized point according to the top-downsituation;and then trace the next contour point until finish the contour linesearching. Continue to seek the contour point to the right, if has, repeat theabove process;If does not, makes the similar search from the right, the topand left edges separately on rectangular boundary.The closed curves searching: Scan each edge of the rectangular grid,if the contour line enters from one edge of the rectangle, then there mustbe another contour point on the other three edges. If one contour point issearched, take it as the original point of the contour line and take down theposition;Increase a hypothesized point according to entering the gridsituation and trace the next contour point until return to the original station.If not, continue to scan until complete the total grid scanning.4. Contour line smoothExtracts the controlling point order of the contour line arrayed wellaccording to the above step, and achieve the anticipated smooth effectthrough calling the smooth disposal procedure many times. The smoothprocedure uses three time of B transect curve smooth procedure to fit.In the paper, the author has researched the principle and the processof plotting the contour map as well as compared the merit and theshortness and suitable condition of several contour mapping methods. Inthe practice, the author developed the contour mapping software bytriangular network with MapX4.5,MapXtreme2.5,Oracle9i,MapInfoProfessional 5.0. The principal modules includes : the grid divided and thegrid value computed module ,the contour point searched module thecontour lines searched and smoothed module, the contour plotted on theMapX active. The principal system function is: the data extracted, importedand updated;the parameters of the contour mapping setting;the option ofthe contour setting and the map layer controlled. The software has beenapplied widely to the produce in the Daqing oil field.