Abstract
Abstract. The approximate value of exterior orientation parameters is needed for air photo bundle adjustment. Usually the air borne GPS/IMU can provide the initial value for the camera position and attitude angle. However, in some cases, the camera’s attitude angle is not available due to lack of IMU or other reasons. In this case, the kappa angle needs to be estimated for each photo before bundle adjustment. The kappa angle can be obtained from the Ground Control Points (GCPs) in the photo. Unfortunately it is not the case that enough GCPs are always available. In order to overcome this problem, an algorithm is developed to automatically estimate the kappa angle for air photos based on phase only correlation technique. This function has been embedded in PCI software. Extensive experiments show that this algorithm is fast, reliable, and stable.
Highlights
The initial approximations of photo’s exterior orientation parameters (EOPs) are essential for air photo bundle adjustment
We developed a new algorithm to automatically determine the kappa angle for air photos based on phase only correlation technique
If the flight line in the object space is projected to the image space, and the azimuth of the flight line can be determined in the image space, the north direction of the photo can be determined
Summary
The initial approximations of photo’s exterior orientation parameters (EOPs) are essential for air photo bundle adjustment. The images are rotated during the preprocessing like lens distortion correction, or the IMU is not available when acquiring photos. In such situations, the attitude angles of the photos need to be estimated before bundle adjustment. If a good distribution and quality of GCPs exist, the attitude angles can be computed [Dewitt, 1996]. For a commercial software, speed is always a key factor to its competitiveness To overcome this challenge, we developed a new algorithm to automatically determine the kappa angle for air photos based on phase only correlation technique.
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