Based On ArcEngine, The Area Calculation And Accuracy Analysis Of The Patch Ellipsoid

Area is an important attribute of polygon feature,and surface area,ellipsoid area and Gaussian projection area are common area statistics.Because the earth's surface fluctuates greatly,so it is difficult to calculate the surface area.In addition,Gauss projection is isometric projection,with area deformation.Therefore,when the accuracy of the area is high,it is necessary to calculate the area of the patch on the ellipsoid surface.According to the Third National Land Survey "Calculation Formulas and Requirements of Theoretical Area of Map and Ellipsoid Area of Patch",this study uses ArcEngine component library developed by ESRI to realize the function of calculating the ellipsoid area of land category patch and the theoretical area of map sheet.By combining theoretical analysis with instance verification,the influence factors and precision of the calculation error of the patch area are analyzed.The main work and research contents are as follows:(1)Two development methods are selected to calculate the ellipsoid area of the patch,one is to extend it by Add-in on the existing Arc GIS desktop software,the other is to develop an independent system.In this paper,the methods of obtaining projection information,interpolating,calculating any trapezoid patch area of ellipsoid,inverse solution of Gaussian projection,calculating the area of complex polygons and calculating the ellipsoid area of arbitrary patch are realized.(2)Choose the Gauss plane coordinate data in the 1980 Xi'an coordinate system and CGCS2000 coordinate system as the experimental data,according to its land category patch data layer,calculate the ellipsoid area in study area.And then,the calculated ellipsoid area is compared with the ellipsoid area calculated by the third land survey software.It is found that the difference between the area value calculated by the developed ellipsoid area calculation tool and the third land survey software is small,which shows that the ellipsoid area calculated by the ellipsoid area calculation tool developed in this paper meets the accuracy requirements.Comparing the area of the ellipsoid with the area of the Gaussian plane,normally,it is found that the area onthe Gaussian plane of the patch is larger than that of the ellipsoid.When the area of the patch is small,the area difference between the Gaussian plane and the area of the ellipsoid is small.When the area of the patch is large,the error between them is large.Therefore,when calculating the area of the patch in the large area,the area of the ellipsoid should be selected as the statistic.(3)The variation law of Gaussian projection area with elevation of projection plane and distance away from central meridian is analyzed,it is found that the higher the elevation of the projection plane,the larger the area deformation is,and it increases linearly in a negative direction.The farther the distance from the central meridian,the larger the area deformation is,showing a square relation.The accuracy analysis of patch ellipsoid area calculation in different coordinate systems,different ellipsoid area calculation formulas and different interpolation distances is carried out,the results show that,there are differences in the calculation values of ellipsoid area in different coordinate systems,and the area difference in the 1980 Xi'an coordinate system and CGCS2000 coordinate system decreases with the increase of latitude.Therefore,when the accuracy of area calculation is required to be high,the impact of conversion of different coordinate systems should be considered.In this paper,the trapezoid area of ellipsoid is calculated by using the ellipsoidal trapezoidal map area formula and the theoretical area formula of map.The results show that the difference between the two formulas is small.By choosing different interpolation distance,analyzing the change of ellipsoid area calculation accuracy with interpolation,it is found that the smaller the interpolation distance is,the higher the calculation accuracy will be.The effect of interpolation on polygon elements with linear distribution is great.When calculating ellipsoid area,we should choose the appropriate interpolation distance with consideration of calculation efficiency and the calculation accuracy.