Development of Software to create a Rectified Image of an Inclined Plane
Figure 4 Acquisition of a series of images with a pair of scales
2.4 Measurement of image coordinates of control points
Figure 5 Measurement of image coordinates of control points
Acquired images are transferred into a computer in an office. Two adjacent images are displayed on the computer screen, and an operator clicks at marked points on scales on the screen. Marked points on a scale are treated as control points. Clicked position of each marked point on the image is measured and recorded as image coordinates of the control points. Figure 5 shows a screen for measuring image coordinates of control points. Measurement of image coordinates of control points is the major manual operation of the software.
2.5 Determination of transformation equation
We adopted the following colinearity equation as a transformation equation of a digital camera image:
( 1 )
( 2 )
where (X, Y, Z) and (u, v) are the ground and image coordinates of the point respectively, (X
o, Y
o, Z
o) and (
w,
f,
k ) are position and attitude of the camera respectively, (u
o, v
o)are the image coordinates of the principal point, and c is the focal length of the camera.
Transformation equations of all images are simultaneously determined by SAPAGO (Simultaneous Adjustment of Photogrammetric And Geometric Observations) developed by the authors. Figure 6 shows geometric constraints of control points used in SAPAGO.
Figure 6 Geometric constraints of control points used in SAPAGO
2.6 Creating a rectified image file
The only work of an operator at this step is to input a size of a pixel of a rectified image to be created. After input of the pixel size of a rectified image a computer executes geometric correction of each image following the determined transformation equation. Finally geometrically corrected images are connected each other to become an image covering the whole of the target slope.
