Currently, modern mapping systems consist of multi-sensor systems, usually referred to as Mobile Mapping Systems (MMS), encompassing a GPS/INS and imaging sensors. System calibration is a crucial process to achieve the expected accuracy of such systems. It involves individual sensor calibration and the mounting parameters calibration (i.e., lever-arm offset and boresight angles) relating the system components. In this paper, a general approach for the mounting parameters calibration of photogrammetric mobile mapping systems is proposed. The proposed method consists of a single-step procedure, which is suitable for single and multi-camera systems. It utilizes a general least squares adjustment concept, i.e., the involved quantities in the mathematical model can be treated either as unknowns, stochastic variables, or error free parameters. The utilization of such concept opens up the possibility of the utilization of the same implementation for different mathematical models which can be considered as special cases of a general model. The implemented procedure consists of an Integrated Sensor Orientation (ISO) where the GPS/INS derived position and orientation information and the system mounting parameters are directly incorporated in the collinearity equations (i.e., modified collinearity equations are utilized). The most general mathematical model can incorporate prior information about the Relative Orientation Parameters (ROP) among the cameras in the ISO. More specifically, the mounting parameters relating the IMU body frame and the reference camera, whose ROP with respect to the other cameras are known, are estimated. The feasibility of the proposed method is demonstrated through experimental results using simulated datasets.