Tài liệu Slide applications of gnss pro software for processing gnss short baseline networks in vietnam

14TH CONFERENCE ON SCIENCE AND TECHNOLOGY APPLICATIONS OF GNSS-PRO SOFTWARE FOR PROCESSING GNSS SHORT BASELINE NETWORKS IN VIETNAM Lau Ngoc Nguyen (1), Huong Thanh Thi Nguyen (2), Hoa Ha Minh (2) (1) Department of Geomatics Engineering, Ho Chi Minh City University of Technology, Vietnam (2) Vietnam Institute of Geodesy and Cartography, Vietnam INTRODUCTION • Research on processing GNSS baselines less than 20 km is important for building surveying control networks. • Short baseline networks allow to use single frequency receivers with cost much lower than dual ones. • All GNSS processing software using in Vietnam are from abroad such as GPSurvey, TGO and TBC from Trimble (USA), LGO from Leica (Switzerland), … • We established GNSS-Pro – the first GNSS processing software made in Vietnam MAIN FEATURES OF GNSS-PRO Single baseline processing Seting up Display and links GNSS data Import Report Network adjustment SINGLE BASELINE PROCESSING • Process single baseline using triple differenced carrier phase measurements. • Repair cycle slips for single baseline. • Process single baseline using double differenced carrier phase measurements to estimate ambiguities. • Resolve ambiguity parameters • Re-process single baseline using double differenced carrier phase measurements with ambiguity corrections. SUB-SESSION PROCESSING METHOD Observation session Cycle slip Subsession 1 X1 Subsession 2 X2 Subsession n Xn Final solution X SUB-SESSION PROCESSING METHOD • Divide a data session into some sub-sessions • Process each sub-session separately to have subsession solutions • Combine sub-session solutions into the final solution Advantages: • A cycle slip, if it exists, only affects a sub-session, and does not affect the remaining sub-sessions. • Ionosphere and multipath can strongly affect some sub-sessions; whereas other sub-sessions are hardly affected. • Exploitation of LAMBDA advantages and the redundancy of a number of GPS and GLONASS satellites help in the ambiguity resolution of each sub-session. • The final solution computed from all sub-session solutions gives results with greater reliability. EXPERIMENTS ON REAL GNSS DATA • Hai Duong cadastral network includes 67 baselines ranging from 2.2 km to 11.3 km • Session length is approximately 1.5 hours. Some centered at 14h local time, strongly affected by the ionosphere • Many site locations have obstructions, strongly affected by the multipath and limited number of observed satellites PROCESSING BY GNSS-PRO Items Values Measurements Carrier phase L1 Elevation cutoff angle 10 GNSS GPS+GLONASS Tropospheric estimation No apply Satellite ephemerides Broadcast • All single baselines are fixed with centimeter accuracy level. • All relative misclosures are less than 10ppm PROCESSING BY TBC Baseline N E U DC13-DC16 -0.021 -0.006 -0.058 DC13-DC17 -0.028 -0.001 -0.081 DC12-DC20 -0.043 -0.057 0.055 TBC - GAMIT DC13-DC16 -0.018 0.303 0.088 DC13-DC17 -0.035 0.331 0.103 DC12-DC20 -0.030 0.071 0.042 Software GNSS Pro GAMIT PROCESSING BY LGO • LGO does not give all fixed solutions as TBC. • There are 6 float baselines. Compared with GNSS-Pro, deviations are several decameters. • The fixed baselines give allowable deviations when compared with GNSSPro. CONCLUSIONS For Hai Dương cadastral network only: • GNSS-Pro gives fixed solutions for all processed baselines with cm accuracy level. • TBC also gives fixed solutions for all processed baselines with RATIO >2. However, three baselines have discrepancies > 1dm (absolute) and 10ppm (relative). • LGO gives 6 float baselines. The fixed baselines give discrepancies at the cm level, true to the nature of the fix status. • GNSS-Pro has more advantages on accuracy, reliability and misclosure checking ability. THANK YOU FOR LISTENING