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Range Geolocation Accuracy of C-/L-Band SAR and its Implications for Operational Stack Coregistration

Yunjun, Zhang and Fattahi, Heresh and Pi, Xiaoqing and Rosen, Paul and Simons, Mark and Agram, Piyush and Aoki, Yosuke (2022) Range Geolocation Accuracy of C-/L-Band SAR and its Implications for Operational Stack Coregistration. IEEE Transactions on Geoscience and Remote Sensing, 60 . Art. No. 5227219. ISSN 0196-2892. doi:10.1109/tgrs.2022.3168509.

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Time series analysis of synthetic aperture radar (SAR) and interferometric SAR generally starts with coregistration for the precise alignment of the stack of images. Here, we introduce a model-adjusted geometrical image coregistration (MAGIC) algorithm for stack coregistration. This algorithm corrects for atmospheric propagation delays and known surface motions using existing models and ensures simplicity and computational efficiency in the data processing systems. We validate this approach by evaluating the impact of different geolocation errors on stacks of the C-band Sentinel-1 and L-band ALOS-2 data, with a focus on the ionosphere. Our results show that the impact of the ionosphere dominates Sentinel-1 ascending (dusk-side) orbit and ALOS-2 data. After correcting for ionosphere using the JPL high-resolution global ionospheric maps, with topside total electron content (TEC) estimated from GPS receivers onboard the Sentinel-1 platforms, solid Earth tides, and troposphere, the mis-registration RMSE reduces by over a factor of four from 0.20 to 0.05 m for Sentinel-1 and from 2.66 to 0.56 m for ALOS-2. The results demonstrate that for Sentinel-1, the MAGIC approach is accurate enough in the range direction for most applications, including interferometry; while for the L-band SAR, it can be potentially accurate enough if topside TEC is available. Based on our current understanding of different error sources, we evaluate the expected range geolocation error budget for the upcoming NISAR mission with an upper bound of the relative geolocation error of 1.3 and 0.2 m for its L- and S-band SAR, respectively.

Item Type:Article
Related URLs:
URLURL TypeDescription ItemMintPy software ItemPySolid package ItemJupyter Notebook
Yunjun, Zhang0000-0001-9441-7082
Fattahi, Heresh0000-0001-6926-4387
Pi, Xiaoqing0000-0002-1949-6769
Rosen, Paul0000-0002-4558-6004
Simons, Mark0000-0003-1412-6395
Agram, Piyush0000-0003-0711-0264
Aoki, Yosuke0000-0002-2539-4144
Additional Information:© 2022 IEEE. Manuscript received January 11, 2022; revised March 18, 2022; accepted April 5, 2022. Date of publication April 18, 2022; date of current version May 9, 2022. This work was supported by the Jet Propulsion Laboratory Advanced Concept, the NASA–ISRO SAR (NISAR) and the Observational Products for End-users from Remote sensing Analysis (OPERA) projects. The Sentinel-1 data were provided by ESA and obtained from Alaska Satellite Facility. The ALOS-2 data were provided by JAXA. The DEM in Japan is provided by GSI. The authors would like to thank Lijun Zhu and Minyan Zhong for their development of PyCuAmpcor, Dennis Milbert for sharing the Fortran program for solid Earth tides calculation and discussion on the along-track time variation of SAR satellite, and Joseph Kennedy for the maintenance of PySolid. We would also like to thank Virginia Brancato, Scott Hensley, and Yujie Zheng for helpful discussions. The research was carried out partly at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. Data Availability: The processed SAR offset and TEC data are available on Zenodo at Code Availability: The ionospheric mapping function is implemented in the MintPy software ( The solid Earth tides code is wrapped as the PySolid package ( under the GPLv3 license. Figures are plotted using Jupyter Notebook and available on GitHub (
Group:Seismological Laboratory
Funding AgencyGrant Number
Subject Keywords:Big-data, coregistration, geodesy, geolocation, interferometric SAR (InSAR), ionosphere, solid Earth tides, synthetic aperture radar (SAR), time series analysis
Record Number:CaltechAUTHORS:20220609-152071000
Persistent URL:
Official Citation:Z. Yunjun et al., "Range Geolocation Accuracy of C-/L-Band SAR and its Implications for Operational Stack Coregistration," in IEEE Transactions on Geoscience and Remote Sensing, vol. 60, pp. 1-19, 2022, Art no. 5227219, doi: 10.1109/TGRS.2022.3168509
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:115107
Deposited By: Tony Diaz
Deposited On:13 Jun 2022 17:36
Last Modified:13 Jun 2022 17:36

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