Slope Surface Nepal (SSN) and GIS Application
On the other hand, the topography surface has to be approximated on the different theories and assumptions. Different software as available in commercial market is based upon the approximate creation of topography surface. Thus the accuracy of the topography surface might be lost behind the acceptable tolerance value, if the points are not densely located to form reasonably good triangles. In fact, the density of the location of the points could also depend upon the scale of the map to be produced. In addition, the location density of the points can also be guided upon the actual slope change of terrain. So the survey points need to be measured by considering all necessary factors described here. Extra points essential to satisfy the basic requirements of TIN data structure can also e created in a linear change of slope surface within the limit of each surface that could be considered as a small piece of polygon. But some of the digital model has also used a curve surface (as presented below) to
approximate the terrain surface on the basis of minimizing the quadratic deviation of sufficient number (minimum 10) points. Such a surface model can be presented by the mathematical equation which is:
H = AX
2+ 2BXY + CY
2+ 2DX + 2EY + F.
Where A, B, C, D, E, and F are the coefficients of the equations and these coefficients can be determined by solving minimum 6 number of equations that could be written as below:
AX12+2BX1Y1+CY12+2DX1+2EY1+F=H4:
AX22+2BX2Y2+CY22+2DX2+2EY2+F=H2:
AX102+2BX10Y10+CY102+2DX10+2EY10+F=H10
However, any approximation of the surface should be based on the basic requirements of the density of the points that should be located within the minimum distance and suitable location as well. These are the various factors that can directly or indirectly affect the accuracy of the topography surface essential to create a real terrain model. Considering the factors just discussed above, a new computerized terrain model named Slope Surface Nepal is developed by the author of this paper with a view to minimize the errors on the formation of the different types of terrain surfaces such as natural surface, design surface, and other type of surfaces. The slope surfaces are represented by a reliable digital model that ensures the generation and creation of the surface points as per the need of different projects depending upon the nature of the slope surface created or selected by the user.
TheSlope Surface Method has been classified as follows:
- Slope Surface of Points
- Slope Surface of Lines
