Digital mapping aerial camera – a measuring instrument

Abstract

The difference between the topographic digital aerial cameras and the analogue ones are analyzed. The first one allows considering a digital aerial camera as a means of measurement. A regular rectangular grid of pixels of digital aerial cameras image sensor is a two-dimensional scale with divisions equal to the physical size of the pixel. It allows determining the position of interest points of the image in the coordinate system of a matrix of pixels, the axis of which is directed along rows and columns of the matrix. Wherein the measured value for aerial cameras, should be considered as the coordinates of the vector pointing from the perspective center to the point of interest in the coordinate system of aerial cameras, the beginning of which is located at the front nodal point of the lens, and the Sz axis is directed along the principal ray. Exactly they are directly used in the solutions of photogrammetric tasks for determination of coordinates of the locality object point. The accuracy of the result of determining the coordinates depends on the accuracy of the coordinates of a direction vector and the accuracy of the exterior orientation parameters of aerial cameras (the image). Metrological characteristics of digital topographic aerial cameras should be considered measurement range (the frame size in pixels and pixel size) and the error of a measuring instrument (the error of the coordinates of a direction vector) as the accuracy characteristics and the parameters of calibration of aerial cameras, allowing to determine the measured values according to indications of measurements with estimates of the errors of the calibration parameters.