9.3.5 Combined adjustment

To achieve maximum accuracy and reliability, a combined adjustment of all information is necessary. In addition to the previously described possibilities of bundle block adjustment, including simultaneous calibration (Section 3.1.2) and three-dimensional adjustment of geodetic networks (Section 3.1.4), combined adjustment further includes integration of additional photogrammetric information, which sets up relations between various photos or between the photos and the object space. These are stereo metric camera conditions, image-station conditions and airborne GPS/IMU data (see also Section 2.1.2). Relevant examples are located in the directories \Bingo\DemoData\Combi_Adj\, ...\Gps_Fairfield\, ...\IMUdata\ and ...\UCX_Deventer\.

This rigorous adjustment cannot be achieved by the customary two-stage adjustment, in which the first step is the adjustment of the control points, and the second step is the photogrammetric adjustment. This even applies when the covariance matrix of the first stage could be fully incorporated in the second step. The last remaining disadvantage then is that the image measurements, which are only added to the second step, cannot contribute to the control of survey measurements in the first step. Thus the statistical test for data-error detection is less rigorous. This disadvantage is eliminated in the combined adjustment.