MEASUREMENTS OF HORIZONTAL DISTANCES USING AERIAL PHOTOGRAPHS CORRECTED BY RADIAL TRIANGULATION AND AEROSKETCHMASTER

Abstract

In this study, we tried to verify the validity of surveying linear distances through Mechanical Radial Triangulation and Aerosketchmaster and uncorrected photographs, as compared to the classic topographic method. Vertical aerial photographs, of an area with slightly sloping topography, with a medium slope of 2%, on a scale of 1:16.000, were used. These were corrected via Mechanical Radial Triangulation using the slotted templets method and with the aid of an aerosketchmaster. The measured alignments were compared directly on top of the photographs and it was verified that the distances of the uncorrected photographs were on an average, 5.9% less than the topographic distances. On the other hand, the distances estimated with a grid base (corrected photographs) were 0.18% larger than the topographic distances. The ";student"; test was applied and was calculated t = - 5.88, which permitted us to conclude that the difference between the topographic measurements and the measurements of the uncorrected aerial photographs were highly significant. The ";student"; test for the topographic measurements, compared with the measurements of the grid base was calculated t = 0.331, and it was concluded that these two methods didn't present a significant difference. A correlation between the survey methods used to measure the distances in the aerial photographs and those taken from the grid base, and the corresponding linear regression, was made. This showed the possibility of making measurements directly on top of the aerial photographs, under the conditions considered, as long as the values presented in table X of Figure IX, are used.