陸基式移動製圖之定位定向混合式整合架構

The development of a Hybrid Integration Scheme for Land Mobile Mapping Applications

早期發展的移動式測繪系統（Mobile Mapping System, MMS），受限於求解外方位參數需控制點，造成應用上受到諸多限制。透過全球導航衛星系統（Global Navigation Satellite System, GNSS）／慣性導航系統（Inertial Navigation System, INS）定位定向整合技術，可於無控制點之環境下，直接求得載台位置與與姿態角，並經過固定臂與軸角化算，可求相機拍攝瞬刻之外方位參數。其後，以共線式及前方交會之原理，即可求得物空間座標，以達到直接地理定位之目的。商業上最常使用的GNSS/INS定位定向整合策略──鬆耦合（Loosely Couple, LC）架構，以GNSS卡曼濾波器（Kalman Filter, KF）及INS/GNSS KF組成。透過GNSS KF計算位置與速度解，並以其結果輸入INS/GNSS KF，用以更新、補償INS的導航資訊；LC具有較簡單且更彈性的架構來取得導航資訊，然而當接收器追蹤衛星少於4顆時，GNSS KF無法提供位置與速度解，此特性於台灣高遮蔽率的都市區域相當不利。另一種整合策略─緊耦合（Tightly Couple, TC）架構，透過唯一INS/GNSS KF接收GNSS原始觀測資料，對INS導航解進行更新、補償；此架構於衛星少於4顆多於1顆時仍可更新，毫無疑問的緊耦合架構更適用於都市區域。然而，台灣地去仍然有許多GNSS完全遮蔽區域，本研究利用TC之結果，虛擬整體測試軌跡之GNSS位置，並以階層式輔助INS之整合，稱為混合式緊耦合（Hybrid Tightly Coupled, HTC）架構，本研究同時利用約20個檢核點，完成基於各軌跡之直接地理定位分析。 Nowadays the most common technologies used for positioning and orientation of a mobile mapping system include using Global Navigation Satellite System (GNSS) as a major positioning sensor and Inertial Navigation System (INS) as the major orientation sensor. Through the GNSS/INS system and calibration parameters the Exterior Orientation parameters (EOPs) of each one image can be derived in the free control point. Using more than two geo-referenced images the object three dimensional coordinate can be intersected and calculated. The integration strategy of the most commercially system is the Loosely Coupled (LC) architecture, that has the simplest architecture using the GNSS solutions to aid the INS navigation information with proper optimization estimator. The LC does combine the two sensors’ solutions when the number of tracked satellite is more than four. In recent year, another commonly integration strategy is known as Tightly coupled (TC) architecture. Because the TC uses the GNSS measurements to aid INS, it can integrate measurements provided by GNSS receiver and INS unless no GNSS satellite is tracked. Obviously, the TC architecture is a better candidate for land based mobile mapping applications than LC in Taiwan. Unfortunately, there are still many GNSS denied environment in the urban area, therefore the TC architecture is still not robust and stable enough for Mobile Mapping System (MMS) application. The objective of this research is to develop Hybrid Tightly Coupled (HTC) to generate virtual and seamless GNSS solution that can be applied in the LC architecture. The present study investigates the impact of LC, TC and HTC INS/GNSS integration schemes on Direct Geo-referencing (DG) in terms of positioning accuracy using the land-based Mobile Mapping System (MMS) van developed at the Department of Geomatics at National Cheng Kung University in Taiwan. The performance analysis is conducted by performing a DG operation with 20 check points that is producing their coordinates without using any ground control points from images taken with the mapping van processed based on LC, TC and HTC schemes, respectively and compare with known coordinates of those check points for further analysis.

Nowadays the most common technologies used for positioning and orientation of a mobile mapping system include using Global Navigation Satellite System (GNSS) as a major positioning sensor and Inertial Navigation System (INS) as the major orientation sensor. Through the GNSS/INS system and calibration parameters the Exterior Orientation parameters (EOPs) of each one image can be derived in the free control point. Using more than two geo-referenced images the object three dimensional coordinate can be intersected and calculated. The integration strategy of the most commercially system is the Loosely Coupled (LC) architecture, that has the simplest architecture using the GNSS solutions to aid the INS navigation information with proper optimization estimator. The LC does combine the two sensors’ solutions when the number of tracked satellite is more than four. In recent year, another commonly integration strategy is known as Tightly coupled (TC) architecture. Because the TC uses the GNSS measurements to aid INS, it can integrate measurements provided by GNSS receiver and INS unless no GNSS satellite is tracked. Obviously, the TC architecture is a better candidate for land based mobile mapping applications than LC in Taiwan. Unfortunately, there are still many GNSS denied environment in the urban area, therefore the TC architecture is still not robust and stable enough for Mobile Mapping System (MMS) application. The objective of this research is to develop Hybrid Tightly Coupled (HTC) to generate virtual and seamless GNSS solution that can be applied in the LC architecture. The present study investigates the impact of LC, TC and HTC INS/GNSS integration schemes on Direct Geo-referencing (DG) in terms of positioning accuracy using the land-based Mobile Mapping System (MMS) van developed at the Department of Geomatics at National Cheng Kung University in Taiwan. The performance analysis is conducted by performing a DG operation with 20 check points that is producing their coordinates without using any ground control points from images taken with the mapping van processed based on LC, TC and HTC schemes, respectively and compare with known coordinates of those check points for further analysis.