DETERMINATION OF COORDINATES DIFFERENCE OF NATIONAL RESERVED FOREST BOUNDARY FROM AERIAL PHOTOGRAPHS AND TRAVERSING

Abstract

The determination of coordinate difference of boundary from aerial photographs and traversing was carried out at Rural Agriculture Education Project of Kasetsart University, Kok Samrong district, Lop Buri province. Area and boundary length are about 48,918 rai and 48 kilometers, respectively. The 1 : 15,000 scale aerial photographs and the 1 : 50,000 base map were utilized in measuring the coordinates and the boundary station parallax as well as the air base of stereo pairs. Heights of the air craft, as boundary station elevations and scale, were calculated for the adjustment of photo coordinates. The adjustment, as the origin reference, is in the same datum of boundary ground coordinates which was surveyed by the stadia traverse and compass rule method. The photo coordinates were compared with the ground coordinates, The coordinate differences, X and Y, were analyzed in multiple linear regression model by stepwise method. Coordinate differences were considered as the dependent variables while height of aircraft and the traverse station of elevation, parallax, scale, and relief displacement were determined as as intendent variables. The regression equations, for the determination of coordinate difference and the adjustment of photo coordinates, were constructed as follow:

                                ΔX = -1651.4657 – 0.5651H + 15.9294P – 0.5727E + 0.1061S

                                ΔY = -3282.7967 – 1.3756H + 27.0393P – 0.3221E + 0.2802S

When     ΔX, ΔY = X, Y Coordinate Difference, respectively, m.

                               H = Height of air craft from MSL., m.

                               P = Parallax of traverse station, mm.

                               S = Scale of traverse station

The coefficient of determination (R²) of both equations were 0.9303 and 0.9422, while the standard error of estimation was 31.8372, 44.3277 respectively. The average of X and Y difference which was calculated by the substitution of the average independent variables, were used in the adjustment and converted the photo coordinates to true ground coordinates according to scale of smaller than 1 : 14,000, 1 : 14,000-1 : 13,500, 1 : 13,500-1 : 13,000, 1 : 13,000 1 : 12,500 and larger than 1 : 12,500. The coordinates difference of X (ΔX) are -172.530, -236.611, -216.123, -68.056, - 108.789 m, respectively and the coordinates difference of Y (ΔY) are -180.233, -274.580, -274.229, -85.153, -168.385 m, respectively.