On the analytical aerial triangulation for hydrographic survey.

Abstract

Aerial triangulation is a function of deciding the geodetic coordinate of photo points used for orientation by using aerial photographs and some control points. If these photo points can be used as the controls for hydrographic survey, the hitherto land triangulation will be replaced by the aerial triangulation. However, as we carried out the aerial photography only along the shoreline due to practical and economical point of view, the image of distribution of land and water is shown on the almost all photographs. Therefore, photo models and strip models used for triangulation are obliged to become imperfect, so that we must consider several problems on the accuracy of aerial triangulation. Since 1964, we have utilized the analytical aerial triangulation in the harbour survey. However, in the present time we are obliged to analyze and discuss the accuracy of aerial triangulation carried out with the imperfect models from the above consideration, in order to find the working guide for the future surveys. In this paper, firstly the practice of the analytical aerial triangulation in our Division is explained, and secondly, analysis of the results obtained during about 3 years is discussed. Finally, we will show the results of the check survey on the controls for hydrographic survey in the Simizu-Okitu district and the trial on the correction of the position error of these controls.