The three different coordinate systems used to perform the mapping can
be seen in Figure 4 (a) below. The world coordinate system (x ,y , z ) of the 3D object is shown together with the colored
orthogonal basis of the local camera coordinate system. The x, y and
z-axis have the colors blue, red and black respectively. The third
coordinate system is generated when the local camera coordinate system
is moved to the center of the camera sensor. (x’ , y’ ) is
the pixel value of the damage in the image while (cposx ,cposy , cposz ) is the position of the camera in world
coordinates. The distance from the camera to the TP in the direction in
which the camera is pointing is given by DCT . fk andfl is the focal length of the camera expressed in pixels along
the horizontal and vertical direction of the camera sensor, these two
parameters are the same for many cameras. cx and cymeasure the number of pixels from the upper left corner to the center of
the camera sensor. The Pitch, Roll and Yaw of the drone (and camera) are
abbreviated with the letters P , R and Y in equation
(1). The yaw angle determines the direction in which the camera is
pointing. This direction is given by the green ray in the Figure. The
first matrix in equation (1) is the rotation matrix that transforms
local camera coordinates into world coordinates. A more detailed
explanation of equation (1) can be found in reference [12].