{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,17]],"date-time":"2026-06-17T22:03:34Z","timestamp":1781733814665,"version":"3.54.5"},"reference-count":51,"publisher":"MDPI AG","issue":"21","license":[{"start":{"date-parts":[[2023,10,25]],"date-time":"2023-10-25T00:00:00Z","timestamp":1698192000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"NASA and UAH","award":["80MSFC22N0004"],"award-info":[{"award-number":["80MSFC22N0004"]}]},{"name":"SERVIR","award":["80MSFC22N0004"],"award-info":[{"award-number":["80MSFC22N0004"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>Operational applications for Synthetic Aperture Radar (SAR) are under development around the world, driven by the free-and-open access of SAR C-band observations that Sentinel-1 of Copernicus has provided since 2014. Radiometric Terrain Correction (RTC) data are key entry-level products for multiple applications ranging from ecosystem to hazard monitoring. Various open-source software packages exist to create RTC products from Single Look Complex (SLC) or Ground Range Detected (GRD) level SAR data, including the Interferometric SAR Computing Environment (ISCE), and the Sentinel-1 Toolbox from the European Space Agency (SNAP 8). Despite the growing availability of RTC software solutions, little work has been performed to identify differences between RTC products generated using different software packages. This work evaluates several Sentinel-1 RTC products and two other Sentinel-1 Analysis Ready Data (ARD) to address the following questions: (1) Which software provides the most accurate RTC product? and (2) how appropriate for analysis are other non-RTC products that are readily available? The RTCs are produced with GAMMA, ISCE-2, and SNAP 8. The other two ARD products evaluated consisted of an angular-based radiometric slope correction produced in Google Earth Engine (GEE) following Vollrath et al., and the Sentinel-1 GRD product. Products are evaluated across 10 sites in a single image approach for (1) radiometric calibration, (2) geometric corrections, and for (3) geolocation quality. In addition, time-series stacks over two sites representing varied terrain and ecosystems are evaluated. The GAMMA-derived RTC product implemented by the Alaska Satellite Facility (ASF) is used as a reference for some of the time-series metrics. The results provide direct guidance and recommendations about the quality of the RTC and ARD products obtained from open source methods. The results indicate that it is not recommended to use the GRD product with no radiometric or geometric corrections for any applications given low performance in multiple metrics. The radiometric calibration and geometric corrections have overall good performance for all open-source solutions, only the non-RTC products (Vollrath et al. and GRD) portray some significant variances in steep terrain. The geolocation assessment indicated that the GRD product has the most significant displacement errors, followed by SNAP 8 with Digital Elevation Model (DEM) matching, and ISCE-2. RTCs created without DEM-matching performed better for both GAMMA and SNAP 8. The time-series results indicate that SNAP 8 products align more closely to GAMMA products than other open-source software in terms of radiometric and geometric quality. This understanding of software performance for SAR image processing is key to designing the affordable and scalable solutions needed for the operational application of SAR Sentinel-1 data.<\/jats:p>","DOI":"10.3390\/rs15215110","type":"journal-article","created":{"date-parts":[[2023,10,25]],"date-time":"2023-10-25T09:54:08Z","timestamp":1698227648000},"page":"5110","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":28,"title":["Evaluating SAR Radiometric Terrain Correction Products: Analysis-Ready Data for Users"],"prefix":"10.3390","volume":"15","author":[{"ORCID":"https:\/\/orcid.org\/0009-0008-2509-6439","authenticated-orcid":false,"given":"Africa I.","family":"Flores-Anderson","sequence":"first","affiliation":[{"name":"Earth System Science Center, University of Alabama in Huntsville, Huntsville, AL 35899, USA"},{"name":"SERVIR Science Coordination Office at Marshall Space Flight Center, Huntsville, AL 35812, USA"},{"name":"Department of Natural Resource Sciences, McGill University, Ste. Anne de Bellevue, QC H9X 3V9, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Helen Blue","family":"Parache","sequence":"additional","affiliation":[{"name":"NASA Marshall Space Flight Center, Huntsville, AL 35812, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1642-7845","authenticated-orcid":false,"given":"Vanesa","family":"Martin-Arias","sequence":"additional","affiliation":[{"name":"Earth System Science Center, University of Alabama in Huntsville, Huntsville, AL 35899, USA"},{"name":"SERVIR Science Coordination Office at Marshall Space Flight Center, Huntsville, AL 35812, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Stephanie A.","family":"Jim\u00e9nez","sequence":"additional","affiliation":[{"name":"Earth System Science Center, University of Alabama in Huntsville, Huntsville, AL 35899, USA"},{"name":"SERVIR Science Coordination Office at Marshall Space Flight Center, Huntsville, AL 35812, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kelsey","family":"Herndon","sequence":"additional","affiliation":[{"name":"Earth System Science Center, University of Alabama in Huntsville, Huntsville, AL 35899, USA"},{"name":"SERVIR Science Coordination Office at Marshall Space Flight Center, Huntsville, AL 35812, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0006-4053-2126","authenticated-orcid":false,"given":"Stefanie","family":"Mehlich","sequence":"additional","affiliation":[{"name":"Earth System Science Center, University of Alabama in Huntsville, Huntsville, AL 35899, USA"},{"name":"SERVIR Science Coordination Office at Marshall Space Flight Center, Huntsville, AL 35812, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2491-526X","authenticated-orcid":false,"given":"Franz J.","family":"Meyer","sequence":"additional","affiliation":[{"name":"Geophysical Institute, University of Alaska, Fairbanks, AK 99775, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Shobhit","family":"Agarwal","sequence":"additional","affiliation":[{"name":"Google, Inc., Mountain View, CA 94043, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Simon","family":"Ilyushchenko","sequence":"additional","affiliation":[{"name":"Google, Inc., Mountain View, CA 94043, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Manoj","family":"Agarwal","sequence":"additional","affiliation":[{"name":"Google, Inc., Mountain View, CA 94043, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7529-2074","authenticated-orcid":false,"given":"Andrea","family":"Nicolau","sequence":"additional","affiliation":[{"name":"Spatial Informatics Group, LLC, 2529 Yolanda Ct, Pleasanton, CA 94566, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Amanda","family":"Markert","sequence":"additional","affiliation":[{"name":"Earth System Science Center, University of Alabama in Huntsville, Huntsville, AL 35899, USA"},{"name":"SERVIR Science Coordination Office at Marshall Space Flight Center, Huntsville, AL 35812, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9999-1219","authenticated-orcid":false,"given":"David","family":"Saah","sequence":"additional","affiliation":[{"name":"Spatial Informatics Group, LLC, 2529 Yolanda Ct, Pleasanton, CA 94566, USA"},{"name":"Department of Environmental Science, University of San Francisco, San Francisco, CA 94117, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Emil","family":"Cherrington","sequence":"additional","affiliation":[{"name":"Earth System Science Center, University of Alabama in Huntsville, Huntsville, AL 35899, USA"},{"name":"SERVIR Science Coordination Office at Marshall Space Flight Center, Huntsville, AL 35812, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2023,10,25]]},"reference":[{"key":"ref_1","unstructured":"Woodhouse, I.H. (2006). Introduction to Microwave Remote Sensing, Taylor Francis."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"1104","DOI":"10.1016\/j.scitotenv.2019.06.494","article-title":"Synthetic aperture radar sensitivity to forest changes: A simulations-based study for the Romanian forests","volume":"689","author":"Tanase","year":"2019","journal-title":"Sci. Total. Environ."},{"key":"ref_3","unstructured":"Rosen, P., Gurrola, E., Sacco, G.F., and Zebker, H. (2012, January 23\u201326). The InSAR Scientific Computing Environment. Proceedings of the 9th European Conference on Synthetic Aperture Radar, EUSAR 2012, Nuremberg, Germany."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"112159","DOI":"10.1016\/j.rse.2020.112159","article-title":"SAR data for tropical forest disturbance alerts in French Guiana: Benefit over optical imagery","volume":"252","author":"Bouvet","year":"2021","journal-title":"Remote Sens. Environ."},{"key":"ref_5","unstructured":"Flores-Anderson, A.I., Herndon, K.E., Thapa, R.B., and Cherrington, E. (2019). The SAR Handbook: Comprehensive Methodologies for Forest Monitoring and Biomass Estimation, NASA."},{"key":"ref_6","first-page":"100968","article-title":"Differentiating Oil Palm Plantations from Natural Forest to Improve Land Cover Mapping in Ghana","volume":"30","author":"Abramowitz","year":"2023","journal-title":"Remote Sens. Appl. Soc. Environ."},{"key":"ref_7","doi-asserted-by":"crossref","unstructured":"Al-Ekabi, C., and Ferretti, S. (2018). Yearbook on Space Policy 2016: Space for Sustainable Development, Springer International Publishing.","DOI":"10.1007\/978-3-319-72465-2"},{"key":"ref_8","doi-asserted-by":"crossref","unstructured":"Markert, K.N., Markert, A.M., Mayer, T., Nauman, C., Haag, A., Poortinga, A., Bhandari, B., Thwal, N.S., Kunlamai, T., and Chishtie, F. (2020). Comparing Sentinel-1 Surface Water Mapping Algorithms and Radiometric Terrain Correction Processing in Southeast Asia Utilizing Google Earth Engine. Remote Sens., 12.","DOI":"10.3390\/rs12152469"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"1115","DOI":"10.1109\/36.536527","article-title":"Radiometric slope correction of synthetic-aperture radar images","volume":"34","author":"Ulander","year":"1996","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"3081","DOI":"10.1109\/TGRS.2011.2120616","article-title":"Flattening gamma: Radiometric terrain correction for SAR imagery","volume":"49","author":"Small","year":"2011","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"337","DOI":"10.1016\/j.rse.2006.09.002","article-title":"Generation of geometrically and radiometrically terrain corrected SAR image products","volume":"106","author":"Loew","year":"2007","journal-title":"Remote Sens. Environ."},{"key":"ref_12","unstructured":"Flores-Anderson, A.I., Herndon, K., Thapa, R., and Cherrington, E. (2019). SAR Handbook: Comprehensive Methodologies for Forest Monitoring and Biomass Estimation, NASA."},{"key":"ref_13","unstructured":"CEOS (2021). CEOS Analysis Ready Data Governance Framework, CEOS. Technical Report October."},{"key":"ref_14","unstructured":"(2022, January 15). ESA. SNAP Download. Available online: https:\/\/step.esa.int\/main\/download\/snap-download\/."},{"key":"ref_15","unstructured":"Werner, C., Wegm\u00fcller, U., Strozzi, T., and Wiesmann, A. (2000, January 16). Gamma SAR and the interferometric processing software. Proceedings of the Ers-Envisat Symposium, Gothenburg, Sweden."},{"key":"ref_16","unstructured":"Kristenson, H., Kennedy, J.H., and Johnston, A. (2022, April 20). ASFHyP3\/hyp3-docs HyP3 Docs v0.3.26. Available online: https:\/\/zenodo.org\/records\/5935091."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"18","DOI":"10.1016\/j.rse.2017.06.031","article-title":"Google Earth Engine: Planetary-scale geospatial analysis for everyone","volume":"202","author":"Gorelick","year":"2017","journal-title":"Remote Sens. Environ."},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Vollrath, A., Mullissa, A., and Reiche, J. (2020). Angular-based radiometric slope correction for Sentinel-1 on google earth engine. Remote Sens., 12.","DOI":"10.3390\/rs12111867"},{"key":"ref_19","unstructured":"Meyer, F.J., Logan, T., Nicoll, J., Hogenson, K., and Gens, R. (2016). Prototyping Radiometrically Terrain Corrected Sentinel-1 Large-Scale. A Short Intro to the Alaska Satellite Facility (ASF), UAF."},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Truckenbrodt, J., Freemantle, T., Williams, C., Jones, T., Small, D., Dubois, C., Thiel, C., Rossi, C., Syriou, A., and Giuliani, G. (2019). Towards sentinel-1 SAR analysis-ready data: A best practices assessment on preparing backscatter data for the cube. Data, 4.","DOI":"10.3390\/data4030093"},{"key":"ref_21","unstructured":"The European Space Agency (ESA) (2023). Sentinel-1 SAR Technical Guide: Ground Range Detected, Technical Report; The European Space Agency (ESA)."},{"key":"ref_22","first-page":"101979","article-title":"Primitives as building blocks for constructing land cover maps","volume":"85","author":"Saah","year":"2020","journal-title":"Int. J. Appl. Earth Obs. Geoinf."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"82","DOI":"10.1016\/j.jenvman.2014.07.047","article-title":"Development of 2010 national land cover database for the Nepal","volume":"148","author":"Uddin","year":"2015","journal-title":"J. Environ. Manag."},{"key":"ref_24","unstructured":"Uddin, K., Matin, M.A., Khanal, N., Maharjan, S., Bajracharya, B., Tenneson, K., Poortinga, A., Quyen, N.H., Aryal, R.R., and Saah, D. (2021). Earth Observation Science and Applications for Risk Reduction and Enhanced Resilience in Hindu Kush Himalaya Region: A Decade of Experience from SERVIR, Springer International Publishing."},{"key":"ref_25","unstructured":"MapBiomas (2019). Proyecto MapBiomas Amazonia\u2014Coleccion 2 Version 2, MapBiomas."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1029\/2005RG000183","article-title":"The Shuttle Radar Topography Mission","volume":"45","author":"Farr","year":"2007","journal-title":"Rev. Geophys."},{"key":"ref_27","unstructured":"Jim\u00e9nez, S.A. (2023, March 10). SERVIR RTC Comparison Geolocation Points and Results. Available online: https:\/\/zenodo.org\/records\/7893458."},{"key":"ref_28","unstructured":"Maxar Technologies (2022). Imagery Basemaps, Maxar Technologies. Technical Report."},{"key":"ref_29","unstructured":"European Space Agency European Space Imaging (2022). WorldView-1 Full Archive and Tasking, European Space Agency European Space Imaging. Technical Report."},{"key":"ref_30","unstructured":"European Space Agency European Space Imaging (2022). WorldView-2 Full Archive and Tasking, European Space Agency European Space Imaging. Technical Report."},{"key":"ref_31","unstructured":"European Space Agency European Space Imaging (2022). WorldView-3 Full Archive and Tasking, European Space Agency European Space Imaging. Technical Report."},{"key":"ref_32","unstructured":"European Space Agency European Space Imaging (2022). GeoEye-1 ESA Archive, European Space Agency European Space Imaging. Technical Report."},{"key":"ref_33","unstructured":"Office for Outer Space Affairs UN-SPIDER Knowledge Portal (2020). Step-by-Step: Mudslides and Associated Flood Detection Using Sentinel-1 Data, Office for Outer Space Affairs UN-SPIDER Knowledge Portal."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"e2022EA002431","DOI":"10.1029\/2022EA002431","article-title":"Mapping and scaling of in situ above Ground Biomass to regional extent with SAR in the Great Slave Region","volume":"9","author":"Kraatz","year":"2022","journal-title":"Earth Space Sci."},{"key":"ref_35","unstructured":"Bontje, D., Chapman, B., Charbonneu, F., Dadamia, D., Kellndorfer, J., Killough, B., Laban, S., Lavalle, M., Lewis, A., and Metzger, M. (2021). Analysis Ready Data For Land (CARD4L) Normalized Radar Backscatter, Commission on Earth Observation Satellites."},{"key":"ref_36","unstructured":"Google (2020, July 11). Sentinel-1 Algorithms|Google Earth Engine|Google for Developers. Available online: https:\/\/developers.google.com\/earth-engine\/guides\/sentinel1."},{"key":"ref_37","doi-asserted-by":"crossref","unstructured":"Mullissa, A., Vollrath, A., Odongo-Braun, C., Slagter, B., Balling, J., Gou, Y., Gorelick, N., and Reiche, J. (2021). Sentinel-1 sar backscatter analysis ready data preparation in google earth engine. Remote Sens., 13.","DOI":"10.3390\/rs13101954"},{"key":"ref_38","unstructured":"Gamma Remote Sensing (2021). GAMMA Software Information, Gamma Remote Sensing."},{"key":"ref_39","unstructured":"University of Alaska Fairbanks and Alaska Satellite Facility (2023). ALOS PALSAR-Radiometric Terrain Correction, Alaska Satellite Facility-Distributed Active Archive Center. Available online: https:\/\/asf.alaska.edu\/data-sets\/derived-data-sets\/alos-palsar-rtc\/alos-palsar-radiometric-terrain-correction\/."},{"key":"ref_40","first-page":"102214","article-title":"Assessing SAR C-band data to effectively distinguish modified land uses in a heavily disturbed Amazon forest","volume":"94","author":"Nicolau","year":"2021","journal-title":"Int. J. Appl. Earth Obs. Geoinf."},{"key":"ref_41","unstructured":"Alaska Satellite Facility (2016). ASF Evaluation of Sentinel 1A Radiometric Terrain Correction, Alaska Satellite Facility. Technical Report."},{"key":"ref_42","unstructured":"ASF (2023). Introduction to SAR Guide, Alaska Satellite Facility. Technical Report."},{"key":"ref_43","unstructured":"Rosenqvist, A., and Killough, B. (2018). A Layman\u2019s Interpretation Guide to L-Band and C-Band Synthetic Aperture Radar Data, Comittee on Earth Observation Satellites. Technical Report 1."},{"key":"ref_44","unstructured":"Flores-Anderson, A.I., Herndon, K., Rajesh, T., and Cherrington, E. (2019). SAR Handbook: Comprehensive Methodologies for Forest Monitoring and Biomass Estimation, NASA."},{"key":"ref_45","unstructured":"United States Geological Survey (2022). ASFHyP3\/hyp3-docs HyP3 Docs v0.3.26, United States Geological Survey."},{"key":"ref_46","unstructured":"Esri, Inc (2019). ArcMap Near Tool (Analysis), Esri, Inc."},{"key":"ref_47","doi-asserted-by":"crossref","unstructured":"Shiroma, G.H.X. (2023). Product Specification Document for the OPERA Radiometric Terrain-Corrected SAR Backscatter from Sentinel-1 Product, National Aeronautics and Space Administration (NASA).","DOI":"10.1109\/IGARSS52108.2023.10282385"},{"key":"ref_48","doi-asserted-by":"crossref","unstructured":"Navacchi, C., Cao, S., Bauer-Marschallinger, B., Snoeij, P., Small, D., and Wagner, W. (2023). Utilising Sentinel-1\u2019s Orbital Stability for Efficient Pre-Processing of Radiometric Terrain Corrected Gamma Nought Backscatter. Sensors, 23.","DOI":"10.3390\/s23136072"},{"key":"ref_49","unstructured":"SentinelHub (2022). Sentinel-1 GRD, SentinelHub."},{"key":"ref_50","unstructured":"Airbus (2022). Copernicus DEM Copernicus Digital Elevation Model Product Handbook, Airbus."},{"key":"ref_51","unstructured":"Parache, H. (2023, March 10). SAR ARD Opensource Comparison. Available online: https:\/\/github.com\/hbparache\/SAR_ARD_opensource_comparison."}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/15\/21\/5110\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T21:11:44Z","timestamp":1760130704000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/15\/21\/5110"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2023,10,25]]},"references-count":51,"journal-issue":{"issue":"21","published-online":{"date-parts":[[2023,11]]}},"alternative-id":["rs15215110"],"URL":"https:\/\/doi.org\/10.3390\/rs15215110","relation":{},"ISSN":["2072-4292"],"issn-type":[{"value":"2072-4292","type":"electronic"}],"subject":[],"published":{"date-parts":[[2023,10,25]]}}}