Bundle adjustment of spherical images acquired with a portable panoramic image mapping system (PPIMS)

Thanks to the development of mobile mapping technologies, close-range photogrammetry (CRP) has advanced to be an efficient mapping method for a variety of applications. A compact CRP system equipped with multiple cameras and a GPS receiver is one of those advanced portable mapping systems. A portable panoramic image mapping system (PPIMS) was specially designed to capture panoramic images with eight cameras and to obtain the position of image station with a GPS receiver. A PPIMS can be considered as a panoramic CRP system. The coordinates of an object point can be determined by the intersection of panoramic image points. For the implementation, we propose a new concept of photogrammetry by using panoramic images. Eight images captured by PPIMS forms a spherical panorama image (SPI). Instead of using the original images, PPIMS SPIs are then used for photogrammetric triangulation and mapping. Under this circumstance, one SPI is formed for each station, and it is associated with only one set of exterior orientation (EO) parameters. Traditional collinearity equations are not applicable to SPI triangulation and mapping. Therefore, a novel bundle adjustment algorithm is proposed to solve EO of multi-station SPIs. Because PPIMS SPIs are not ideal SPIs, a correction scheme was also developed to correct the imperfect geometry of PPIMS SPI. Two test studies were performed for the data collected at a campus test field of National Cheng Kung University (NCKU) and at a historical site of Tainan. Both cases demonstrate the feasibility of SPI bundle adjustment and applying corrections for PPIMS SPIs necessary for effective for bundle adjustment. Furthermore, the experiment’s results also confirm that SPIs can replace original images for PPIMS triangulation.