The Performance Analysis of a Portable Mobile Mapping System with Different GNSS Processing Strategies

摘要

Over the years, land vehicular based Mobile Mapping Systems (MMSs) have demonstrated that accuracies suitable for all but the most demanding cadastral and engineering applications can be achieved. This result, combined with a reduction in both the time and cost of data collection, made MMS a very interesting technology potentially able to meet the demand of spatial information system operators for rapid spatial data acquisition. However, the high costs involved in the development of such systems limits their growth in the market, so that land vehicular based MMSs are still mainly operated by the companies or institutions that build them. In addition, the primary limitation of such land vehicular based systems in terms of operation flexibility is the dependence of the availability and quality of road networks. Sometime streets in the metropolitan area are too narrow for land vehicle to operate. To allow a wider community of spatial data user to benefit of mobile mapping applications - in particular the lower costs and greater efficiency of data collection, a portable MMS (PMMS), is developed in this study. The proposed PMMS is composed of a tactical grade Inertial Measurement Unit (IMU), dual frequencies Global Navigation Satellite System (GNSS) receiver, two digital cameras, a centralized power supply as well as data storage unit to avoid the use of computer or laptop. Data processing modules including Position and Orientation System (POS) module, mounting calibration (boresight and lever arm) module and close range photogrammetry module are developed in this study. In addition, different GNSS processing strategies applied for proposed PMMS operation including conventional differential GNSS with a physical reference station, differential GNSS with Virtual Reference Station (VRS) and Precise Point Positioning (PPP) are investigated in terms of their Direct Georeferencing (DG) performance. Preliminary results presented in this study by comparing DG results of checking points provided by the proposed PMMS from various scenarios with their known coordinates depicts the absolute 3D positioning accuracy can reach less than 10 centimeters when the object distance is around 20 meters.