You acquired a nadir aerial dataset and did not led a specific calibration step
You submitted an AT, the distortion parameters were computed and your photogroup oriented, but the result is not satisfying. On that kind of dataset we often observe the same spherical deformation due to distortion parameters inaccuracy.
To avoid this problem, we recommend the following:
http://communities.bentley.com/products/3d_imaging_and_point_cloud_software/w/wiki/26457.how-to-calibrate-your-camera-using-contextcapture