Abstract
The early development of mobile mapping system (MMS) was restricted to applications that permitted the determination of the elements of exterior orientation from existing ground control. Mobile mapping refers to a means of collecting geospatial data using mapping sensors that are mounted on a mobile platform. Research works concerning mobile mapping dates back to the late 1980s. This process is mainly driven by the need for highway infrastructure mapping and transportation corridor inventories. In the early nineties, advances in satellite and inertial technology made it possible to think about mobile mapping in a different way. Instead of using ground control points as references for orienting the images in space, the trajectory and attitude of the imager platform could now be determined directly. Cameras, along with navigation and positioning sensors are integrated and mounted on a land vehicle for mapping purposes. Objects of interest can be directly measured and mapped from images that have been georeferenced using navigation and positioning sensors. Direct georeferencing (DG) is the determination of time-variable position and orientation parameters for a mobile digital imager. The most common technologies used for this purpose today are satellite positioning using the Global Navigation Satellite System (GNSS) and inertial navigation using an Inertial Measuring Unit (IMU). Although either technology used along could in principle determine both position and orientation, they are usually integrated in such a way that the IMU is the main orientation sensor, while the GNSS receiver is the main position sensor. However, GNSS signals are obstructed due to limited number of visible satellites in GNSS denied environments such as urban canyon, foliage, tunnel and indoor that cause the GNSS gap or interfered by reflected signals that cause abnormal measurement residuals thus deteriorates the positioning accuracy in GNSS denied environments. This study aims at developing a novel method that uses ground control points to maintain the positioning accuracy of the MMS in GNSS denied environments. At last, this study analyses the performance of proposed method using about 20 check-points through DG process.
Highlights
The development of land-based mobile mapping systems was initiated by two research groups, namely The Center for Mapping at Ohio State University, USA, and the Department of Geomatics Engineering at the University of Calgary, Canada
This study proposes a Mapping Systems (MMS) cart developed at the National Cheng Kung University (NCKU) in Taiwan to verify Direct georeferencing (DG) capability with the photogrammetry technology aiding
Because the control points can be measured by other surveying methods in Global Navigation Satellite Systems (GNSS) outage area and the derived position and attitude are corrected and smoothed track, the accuracy can be significantly ascended during GNSS denied environment
Summary
Known as smoothers, have been applied for the purpose of accurate positioning and orientation parameter determination through post-processing for most of surveying and mobile mapping applications with integrated sensors. In the process of the lever arm calibration, the perspective position of each image ( ) is exactly known after the bundle adjustment, and the calculation about the INS/GNSS position vector ( ) is conducted by the interpolation at the same time. The accuracy of the calibration process is dominated by the quality of the INS/GNSS data and the bundle adjustment results This relationship affects the performance of MMS indirectly. In this case, the distribution of the control points in the image and the quality of the INS/GNSS data are very important during the calibration process. The DG task can be performed exactly works without GCPs
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