Time filter

Source Type

Ji W.,Wuhan University | Dai X.,Tianjin Institute of Surveying and Mapping
Journal of Geomatics | Year: 2014

In this paper, the interferogram was filtered by mean filtering method, median filtering method, periodic pivoting mean filtering method, periodic pivoting median filtering method, and filtering method based on wavelet transform, which were acquired by TerraSAR-X satellites in Nantun mining area. Then we determined which was the best filtering method in this area through a series of indicators, such as residues.

Luo Q.,Tianjin University | Perissin D.,Purdue University | Zhang Y.,CAS National Astronomical Observatories | Jia Y.,Tianjin Institute of Surveying and Mapping
Remote Sensing | Year: 2014

When synthetic aperture radar interferometry (InSAR) technology is applied in the monitoring of land subsidence, the sensor band plays an important role. An X-band SAR system as TerraSAR-X (TSX) provides high resolution and short revisit time, but it has no capability of global coverage. On the other side, an L-band sensor as Advanced Land Observing Satellite-Phased Array L-band Synthetic Aperture Radar (ALOS-PALSAR) has global coverage and it produces highly coherent interferograms, but it provides much less details in time and space. The characteristics of these two satellites from different bands can be regarded as complementary. In this paper, we firstly present a possible strategy for X-band optimized acquisition planning combining with L-band. More importantly, we also present the multi-temporal InSAR (MT-InSAR) analysis results from 23 ALOS-PALSAR images and 37 TSX data, which show the complementarity of L- and X-band allows measuring deformations both in urban and non-urban areas. Furthermore, the validation between MT-INSAR and leveling/GPS has been carried out. The combination analysis of L- and X-band MT-InSAR results effectively avoids the limitation of X-band, providing a way to define the shape and the borderline of subsiding center and helps us to understand the subsidence mechanism. Finally, the geological interpretation of the detected subsidence center is given. © 2014 by the authors.

Wei E.,Wuhan University | Jin S.,Chinese Academy of Sciences | Zhang Q.,Wuhan University | Zhang Q.,Tianjin Institute of Surveying and Mapping | And 3 more authors.
Advances in Space Research | Year: 2013

Autonomous navigation of Mars probe is a main challenge due to the lack of dense ground tracking network measurements. In this paper, autonomous navigation of the Mars probe Orbits is investigated using the X-ray pulsars. A group of X-ray pulsars with high ranging accuracy are selected based on their properties and an adaptive extended Kalman filter is developed to incorporate the Mars probe dynamics and pulsar-based ranging measurements. Results of numerical experiment show that the three-dimensional positioning accuracy can achieve 750m in X-axis, 220m in Y-axis and 230m in Z-axis, which is much better than the positioning results by current Very Long Baseline Interferometry (VLBI) or Doppler observations with the accuracy of 150 km or several kilometers, respectively. © 2012 COSPAR. Published by Elsevier Ltd. All rights reserved.

Luo Q.,Chinese University of Hong Kong | Perissin D.,Chinese University of Hong Kong | Lin H.,Chinese University of Hong Kong | Zhang Y.,Chinese University of Hong Kong | Wang W.,Tianjin Institute of Surveying and Mapping
IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing | Year: 2014

This paper illustrates the first wide area study over Tianjin suburbs of China using persistent scatterers interferometry (PSI) technique for ground subsidence monitoring via high-resolution TerraSAR-X (TSX) SAR data. The deformation rate and the displacement history of the subsiding areas from April 29, 2009 to November 11, 2011 have been reconstructed. The results demonstrate the capability of applying PSI technique to high-resolution SAR time series imageries for monitoring of the subsidence of multiple towns and large-scale man-made linear features (LMLFs) such as railways, highways, and power lines. The comprehensive uncertainties were analyzed between PSI results and ground-leveling data whose densities are very different in both spatial and temporal domains. The overall results show a good agreement with each other. We also found that the underground water extraction and lithological character are the two important potential explanations to the location and shape of the subsiding centers. © 2013 IEEE.

Yin D.,Tianjin Institute of Surveying and Mapping | Mei L.,Tianjin Institute of Surveying and Mapping
Journal of Geomatics | Year: 2014

The DXF format is the most commonly used graphics CAD Graphics Interchange Format. Because it is easy to read and write, gradually it is developed into auniversal format. This paper firstly studies the entity data stored in the DXF file, then uses the C# language to operate the DXF file directly and this is independent of the CAD environment. Thus the map coordinate. conversion function is completed. Finally, combining with the specific project example, the correctness of software is verified.

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