Abstract: Using the database windowing functions the dense grids containing a bunch contour lines within them can be generated.The grid bunches of contour lines are independent from all neighbor grids,therefore,they can serve as the basis for deriving the aspect vectors.The basic principle lies in simple vector composition.After the representing of vector into coordinates,the general direction of every contour line can be seen as the composition of all of its vectors(line segments): sum of coordinate differences(the first vector composition).Further more,the grid terrain aspect can be calculated as the vector sum of all contour lines within the grid(the second vector composition).Because the density of contour line can differ from one place to another,it is unavoidable existence of empty grids which causes the necessity to research the appropriate method for aspect interpolation(the third vector composition).Due to the using of same method of vector composition in entire process of aspect calculation,therefore,the method proposed in this paper can be considered as the simplest one.