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Remote Sens. 2018, 10(9), 1405; https://doi.org/10.3390/rs10091405

Investigations on the Coregistration of Sentinel-1 TOPS with the Conventional Cross-Correlation Technique

1
Lyles School of Civil Engineering, Purdue University, West Lafayette, IN 47907, USA
2
School of Mechanical Engineering, Northwestern Polytechnical University, Xi’an 710072, China
*
Author to whom correspondence should be addressed.
Received: 12 June 2018 / Revised: 18 August 2018 / Accepted: 20 August 2018 / Published: 4 September 2018
(This article belongs to the Section Remote Sensing Image Processing)
Full-Text   |   PDF [36784 KB, uploaded 4 September 2018]   |  

Abstract

In Sentinel-1 TOPS mode, the antenna sweeps in the azimuth direction for the purpose of illuminating the targets with the entire azimuth antenna pattern (AAP). This azimuth sweeping introduces an extra high-frequency Doppler term into the impulse response function (IRF), which poses a more strict coregistration accuracy for the interferometric purpose. A 1/1000 pixel coregistration accuracy is required for the interferometric phase error to be negligible, and the enhanced spectral diversity (ESD) method is applied for achieving such accuracy. However, since ESD derives miscoregistration from cross-interferometric phase, and phase is always wrapped to [ π , π ) , an initial coregistration method with enough accuracy is required to resolve the phase ambiguity in ESD. The mainstream for initial coregistration that meets this requirement is the geometrical approach, which accuracy mainly depends on the accuracy of orbits. In this article, the authors propose to investigate the feasibility of using the conventional coregistration approach, namely the cross-correlation-and-rigid-transformation, as the initial coregistration method. The aim is to quantify the coregistration accuracy for cross-correlation-and-rigid-transformation using the Cramér-Rao lower bound (CRLB) and determine whether this method could eventually help to resolve the phase ambiguities of ESD. In addition, we studied the feasibility and robustness of the cross-correlation plus ESD under different conditions. For validation, we checked whether the cross-correlation plus ESD approach could reach the same coregistration accuracy as geometrical plus ESD approach. In general, for large areas with enough coherence and little topography variance, the cross-correlation method could be used as an alternative to the geometrical approach. The interferogram from the two different approaches (with ESD applied afterward) shows a negligible difference under such circumstances. View Full-Text
Keywords: TOPS; coregistration; cross correlation; rigid transformation; Cramér-Rao lower bound TOPS; coregistration; cross correlation; rigid transformation; Cramér-Rao lower bound
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Qin, Y.; Perissin, D.; Bai, J. Investigations on the Coregistration of Sentinel-1 TOPS with the Conventional Cross-Correlation Technique. Remote Sens. 2018, 10, 1405.

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