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Zhang Z.,Wuhan University | Zhang Z.,Key Laboratory of Precise Engineering | Kong N.,Wuhan University | Shen F.,Wuhan University | Lu L.,East China Investigation and Design Institute
Journal of Geomatics | Year: 2010

We introduce a kind of mobile deformation monitoring scheme used by georobot for subway tunne, including the design for datum points and monitor points, and method for selecting stable datum points. This scheme is proved to effectivbe by combining with a subway tunnel monitoring project and provides rreference for similar project.

Wang D.,Chinese Academy of Agricultural Sciences | Wang D.,Wuhan University | Yang J.,Xidian University | Sun G.,Xidian University | And 7 more authors.
Photogrammetric Engineering and Remote Sensing | Year: 2014

Due to the costs, sensitivity, and export policies of many governments, universities, and research institutions, particularly in developing countries, the ability to purchase, install and maintain high-accuracy inertial navigation system (INS) and global positioning system (GPS) is restricted. This paper presents a new method for SAR imaging and interferometry using parameters estimated from raw data. First, methods for determining the order of real and imaginary parts within the raw data images, and for determining chirp rate polarity are proposed. Second, a selection of parameters, including the forward effective velocities of the sensor, the near range distance, and the squint angle, are extracted using the Doppler centroid and Doppler rate. Finally, we create single look complex (SLC) images, coherence maps, digital elevation models (DEMs), and dual-pass differential unwrapped phase maps. The level of accuracy shown in this comparative study suggests that the proposed method is acceptable for creating the featured SAR products and is suitable for real world applications. This method and result is particularly relevant for systems which suffer from a lack of high-accuracy positional metadata. © 2014 American Society for Photogrammetry and Remote Sensing.

Yi Z.,Central South University | Yi Z.,Key Laboratory of Precise Engineering | Chen Y.,Hong Kong Polytechnic University | Zhu J.,Central South University | And 3 more authors.
Acta Geodaetica et Cartographica Sinica | Year: 2011

Real time precise point positioning (PPP) needs real time GPS orbit and clock product. An approach to real time PPP using regional GPS continuously operating reference stations (CORS) data and IGS ultra-rapid (IGU) product is proposed. First, real time GPS satellite clock is estimated using regional CORS data and IGU real time predicted orbit product. Then real time PPP positioning for user GPS receiver is conducted using the estimated real time satellite clock and IGU real time predicted orbit. Experiments show that the approach can be used to get centimeter level PPP result, and can extend PPP service area several hundreds kilometer away from CORS.

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