Direct / Integrated Sensor Orientation - Pros and Cons

The direct geo-referencing of sensors based on a combination of relative kinematic GPS-positioning and inertial measurement units (IMU) has reached a high accuracy level and growing application. It includes the advantage of a very flexible use, independent upon control points which are only required for the system calibration and independent upon block or strip configurations. It is in use in areas with difficult access, as well as for standard applications. The direct georeferencing is a prerequisite for the economic use of small format digital images instead of standard aerial photos. Projects with standard accuracy requirements can be handled without problems. Only some limitations may appear for the model setup; disturbing y-parallaxes cannot be avoided with the today dominating application of standard photographic aerial cameras. But an improvement of individual models or a whole block by a combined adjustment together with image coordinates of tie points can solve this problem. For large scale projects with higher accuracy requirements an integrated sensor orientation by a bundle block adjustment with the orientations as observations and a minimal number of control points is proposed. An overview of the status of direct and integrated sensor orientation will be given.