Integrated multi-sensor systems, with their major progress in terms of sensor resolution, data rate and operational flexibility, have become a very attractive mapping tool over the last decade. In aerial mapping application, for example, Exterior Orientation (EO) parameters for the imaging sensors are required. Using the integrated Differential Global Positioning System (DGPS) with Inertial Measurement Units (IMU), direct determination of the EO parameters can be obtained from the integrated system navigation solution. This process is referred to as Direct Georeferening (DG). DG provides substantial benefits over the indirect determination method of estimating the EO parameters from conventional Aerial Triangulation (AT) techniques using a block of images with a sufficient number of known control points. These benefits include the ability to map remote and inaccessible regions, and by replacing tie point measurements/matching and AT, significant cost-savings can be obtained for projects that do not require stereo models (such as projects with existing DEM or single image). The accuracy of DG, however, is limited by the accuracy attainable by the DGPS and any residual datum calibration errors. These can typically be as large as 10 cm RMSE, which is not sufficient for some large scale mapping applications. However, by combining the direct EO data a traditional block adjustment, AT techniques can be used to remove the residual errors in the solution. This technique is known as Integrated Sensor Orientation (ISO). It has several advantages over traditional AT, primarily because the stable geometry provided by direct EO can reduce the number of required GCP and tie-point to a minimum. At the same time, ISO provides an excellent tool for Quality Control/Quality Assurance (QC/QA) of the EO derived from a DG system. This paper examines the factors that determine the system performance for ISO. In addition, examples are given to illustrate the expected accuracy of an aerial mapping project using ISO under different qualities of DGPS/IMU data.
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