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Li W.,Wuhan University | Cheng P.,Chinese Academic of Surveying and Mapping | Bi J.,Chinese Academic of Surveying and Mapping
Wuhan Daxue Xuebao (Xinxi Kexue Ban)/Geomatics and Information Science of Wuhan University | Year: 2011

A new method of regional ionosphere delays' calibration based on uncombined precise point positioning (PPP) is proposed in this paper, and the accuracy is assessed by interpolating the calibrated delays at a user station with single frequency simulated kinematic PPP implementation. The results show that the accuracy of interpolation is better than 1 dm and less affected by the ionosphere activity; the positioning accuracy of single frequency simulated kinematic PPP are 4~5 cm for panel and better than 1 dm for vertical respectively. Comparatively, two reference solutions are also obtained in single frequency simulated kinematic PPP mode, with eliminating ionosphere delays either by forming semi-combination observations or interpolated values from global ionosphere maps (GIM), the positioning accuracy of both cases are approximately 4~7 dm and 1 m for the panel and vertical respectively.


Wei L.,Wuhan University | Pengfei C.,Chinese Academic of Surveying and Mapping | Jinzhong B.,Chinese Academic of Surveying and Mapping | Hanjiang W.,Chinese Academic of Surveying and Mapping | Hua W.,Wuhan University
Journal of Earth System Science | Year: 2012

A new method for the calibration of regional ionospheric delay based on uncombined precise point positioning (U-PPP) is proposed in this study. The performance of the new method was comparatively validated in terms of its accuracy and robustness with respect to the phase-smoothed pseudorange (PSP) method through two short-baseline experiments. Accuracy of the PPP-derived ionospheric delays was further assessed by interpolating them to a user station to perform single-frequency simulated kinematic PPP. Two 24-hr period datasets of four continuous operation reference system (CORS) stations were analyzed, collected during calm and disturbed ionospheric conditions, respectively. The single-frequency GPS observables from a user station, that were a-priori corrected by the interpolated ionospheric delays, were utilized to implement single-frequency PPP (SF-PPP). The results show that interpolation accuracy is better than 1 dm and, with the proposed method, is less affected by the ionospheric activity; meanwhile, positioning accuracy of SF-PPP was 4∼5 cm (horizontal) and better than 1 dm (vertical). For comparison, two reference SF-PPP solutions were also obtained, in which the ionospheric delays are eliminated either by forming semi-combination observations or by using global ionosphere maps (GIM) model values; in both cases the positioning accuracy was only 4∼7 dm (horizontal) and 1 m (vertical). These results provide a further demonstration of the performance of PPP-based regional ionospheric calibration in the parameter domain. © Indian Academy of Sciences.


Yang S.,Hubei University | Huang G.,Chinese Academic of Surveying and Mapping | Zhao Z.,Chinese Academic of Surveying and Mapping
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives | Year: 2010

In the western region of China, Synthetic Aperture Radar images have been used in extraction of topographic maps. Stero mapping with stereoscopic image pair is very useful for extraction of feature elements (roads, buildings and other surface features) from SAR image. The basis of stereo-mapping is stereoscopic image pair, of which the vertical parallax must be removed, and the horizontal parallax reserved. This paper presents a method of generating SAR stereoscopic image pair based on Digital Elevation Model, which is used in stereo-mapping. First of all, orientation of SAR image must be completed; then according to DEM, stereoscopic image can be generated through image re-sampling along the range direction from original image. The vertical parallax will be removed, when re-sampling, and the horizontal parallax will be reconstructed with central projection or slant-range projection. There are two ways to generate stereoscopic images from single original image or two different original images. The two images generated from single original image are called mono-source pair. The two images generated from the two different images are called dual-source pair. Experiment is done in this paper with high-resolution space-borne SAR images. Mono-source and dual-source stereoscopic image pairs are generated with central and slant-range projection, and feature elements of topographic map are extracted with the image pairs in the experiment. It proves that the method above is feasible.


Yang S.,Wuhan University | Wang N.,Chinese Academic of Surveying and Mapping | Huang G.,Chinese Academic of Surveying and Mapping | Zhao Z.,Chinese Academic of Surveying and Mapping
International Radar Symposium, IRS 2011 - Proceedings | Year: 2011

SAR stereo image pair is not suitable for stereoscopic observation of human eyes because of its projection style, slant range projection. Simulating SAR stereo image pair to a central projection stereo image pair based on existing DEM (e.g. SRTM), image pair suitable for human eyes' stereoscopic observation can be obtained. After image simulation, establishing map between simulated image coordinates and original SAR image coordinates, and transforming parallax of simulated image pair from stereo-measurement to parallax of original SAR image pair, elevation can be calculated according to the original SAR stereo geometric model. The stereo model about coordinate map between simulated images coordinates and geographical coordinates will be established in this paper. The difficult point in this model is the map between simulated image coordinates and original SAR image coordinates. The calculation from simulated image coordinates to original SAR image coordinates is based on simulated imaging model and elevation lookup table of simulation re-sampling. And the opposite procedure is based on the map table obtained from image coordinates triangulation (TIN). Experiments with high resolution airborne SAR images of China prove that the method of this paper is available. © 2011 DGON.

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