Abstract
Mobile mapping systems (MMS) are increasingly used for many photogrammetric and computer vision applications, especially encouraged by the fast and accurate geospatial data generation. The accuracy of point position in an MMS is mainly dependent on the quality of calibration, accuracy of sensor synchronization, accuracy of georeferencing and stability of geometric configuration of space intersections. In this study, we focus on multi-camera calibration (interior and relative orientation parameter estimation) and MMS calibration (mounting parameter estimation). The objective of this study was to develop a practical scheme for rigorous and accurate system calibration of a photogrammetric mapping station equipped with a multi-projective camera (MPC) and a global navigation satellite system (GNSS) and inertial measurement unit (IMU) for direct georeferencing. The proposed technique is comprised of two steps. Firstly, interior orientation parameters of each individual camera in an MPC and the relative orientation parameters of each cameras of the MPC with respect to the first camera are estimated. In the second step the offset and misalignment between MPC and GNSS/IMU are estimated. The global accuracy of the proposed method was assessed using independent check points. A correspondence map for a panorama is introduced that provides metric information. Our results highlight that the proposed calibration scheme reaches centimeter-level global accuracy for 3D point positioning. This level of global accuracy demonstrates the feasibility of the proposed technique and has the potential to fit accurate mapping purposes.
Highlights
Mobile mapping system (MMS) is a photogrammetric mapping agent that is usually defined as a set of navigation (global navigation satellite system (GNSS) and inertial measurement unit (IMU)) and remote sensors—such as cameras, lidar, and odometer sensors—integrated in a common moving platform [1]
Direct geo-referencing is the process to find position and orientation of captured images (EOPs) in a global reference frame without employing any ground control point (GCP), which requires the integration of additional sensors such as GNSS receivers and IMU sensors into the camera’s mounted frame
In the process of MMS calibration, initial values of lever-arm and boresight misalignments are estimated by independently compiling a local network of few shots, connecting the local network to the global frame of GNSS/IMU sensors
Summary
Mobile mapping system (MMS) is a photogrammetric mapping agent that is usually defined as a set of navigation (global navigation satellite system (GNSS) and inertial measurement unit (IMU)) and remote sensors—such as cameras, lidar, and odometer sensors—integrated in a common moving platform [1]. Direct geo-referencing is the process to find position and orientation of captured images (EOPs) in a global reference frame without employing any ground control point (GCP), which requires the integration of additional sensors such as GNSS receivers and IMU sensors into the camera’s mounted frame. This integration either provides initial values for positions and orientations of the camera shots as weighted observations in the BBA, or helps the system to instantly estimate position vectors and Euler angles of shots [45]. Our results demonstrate that sub-decimeter level accuracy is achievable by this technique
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