عنوان مقاله [English]
نویسنده [English]چکیده [English]
This paper presents a report by the authors of the paper to show the Earth's Crust subsidence in a Venezuelan oil field by combining GPS observations with accurate levelling. The area is 50 by 50 km2. The mathematical model used is derived from the University of New Brunswick’s method of analyzing form change through GPS hybrid observation and precise levelling. Before launching this project, the group had tested their method in a number of Canadian experimental networks (with a range of 0.7 to 30 km) using TI4100, WM101 and Trimble 4000 SX receivers, and by the WM101 receiver in a section of Venezuelan network. To estimate accuracy, the MINQE method, comparison of the determined subsidence with GPS and accurate levelling have been used. The results show that with the C / A receiver code and the geometric arrangement of satellites in the winter of 1989, the altitude component (h) in the short and medium ranges (up to a maximum of 30 km) can be determined with precision of the order of 15 mm in favorable weather conditions, and with precision of 30 mm in hot and humid conditions.