| Elevation gradient is a basic calculation of slope algorithm,In slope algorithm ?=arctan?p2+q2?1/2,elevation gradient are p and q.The differences of varied slope algorithms are mainly due to the different algorithms of p and q,and therefore the basis of slope algorithms precision evaluation is the research on properties and precision of p and q algorithms.The differences of varied slope algorithms are mainly due to the different algorithms of p and q,p and q is the research origin of theoretical model of slope distribution.Four different terrain types sample sites were selected,including loess hills and qinling mountains in shaanxi province,undulate hill in heilongjiang province and hengduan mountains in yunnan province.Seven different algorithms were used to calculate the height gradient?p,q?.Statistical distribution characteristics,spatial structure characteristics,algorithm precision,stability and uncertainty were analyzed.The characteristics of different resolution elevation gradient are analyzed in undulate hill and loess hills.The four fundamental properties ofp and qa will be explained from the perspective of physics and mathematics.The main results of this paper are as follows:?1?Statistical distribution of elevation gradient:the mean values of p and q are almost zero,p and q are independent from each other,the variance ofp and q are equal,and they follow the pattern of normal distribution??2?Spatial pattern?or structure?:All kinds of algorithms can express the difference between the local structure and the sample area.The more complex terrain,the greater the p and q surface undulation.?3?From the aspect of stability and uncertainty of the algorithm,algorithm 4?the improved Evans-Young algorithm based on Shary?has the best effect.?4?The characteristics of different resolution elevation gradient:With the reduction of the resolution of DEM,the basic properties of p and q have not changed,the texture and structure of p and q surface become simple and smoothing. |
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