{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,24]],"date-time":"2026-04-24T21:38:06Z","timestamp":1777066686452,"version":"3.51.4"},"reference-count":65,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2020,4,24]],"date-time":"2020-04-24T00:00:00Z","timestamp":1587686400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100006124","name":"National Institute of Education","doi-asserted-by":"publisher","award":["SUG-NAP (3\/19 EP)"],"award-info":[{"award-number":["SUG-NAP (3\/19 EP)"]}],"id":[{"id":"10.13039\/501100006124","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>Global measurements of reservoir water levels are crucial for understanding Earth\u2019s hydrological dynamics, especially in the context of global industrialization and climate change. Although radar altimetry has been used to measure the water level of some reservoirs with high accuracy, it is not yet feasible unless the water body is sufficiently large or directly located at the satellite\u2019s nadir. This study proposes a gauging method applicable to a wide range of reservoirs using Sentinel\u20131 Synthetic Aperture Radar data and a digital elevation model (DEM). The method is straightforward to implement and involves estimating the mean slope\u2013corrected elevation of points along the reservoir shoreline. We test the model on six case studies and show that the estimated water levels are accurate to around 10% error on average of independently verified values. This study represents a substantial step toward the global gauging of lakes and reservoirs of all sizes and in any location where a DEM is available.<\/jats:p>","DOI":"10.3390\/rs12081353","type":"journal-article","created":{"date-parts":[[2020,4,24]],"date-time":"2020-04-24T11:42:14Z","timestamp":1587728534000},"page":"1353","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":13,"title":["A Pathway to the Automated Global Assessment of Water Level in Reservoirs with Synthetic Aperture Radar (SAR)"],"prefix":"10.3390","volume":"12","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-1299-1724","authenticated-orcid":false,"given":"Edward","family":"Park","sequence":"first","affiliation":[{"name":"National Institute of Education, Nanyang Technological University, Singapore 637551, Singapore"},{"name":"Asian School of the Environment, Nanyang Technological University, Singapore 637551, Singapore"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2155-8620","authenticated-orcid":false,"given":"Eder","family":"Merino","sequence":"additional","affiliation":[{"name":"Institute of Energy and Environment, University of Sao Paulo, S\u00e3o Paulo 05508-060, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Quinn","family":"W. Lewis","sequence":"additional","affiliation":[{"name":"Department of Geography and Environmental Management, University of Waterloo, Waterloo, ON N2L 3G1, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Eric","family":"O. Lindsey","sequence":"additional","affiliation":[{"name":"Earth Observatory of Singapore, Nanyang Technological University, Singapore 637551, Singapore"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1303-195X","authenticated-orcid":false,"given":"Xiankun","family":"Yang","sequence":"additional","affiliation":[{"name":"School of Geographical Sciences, Guangzhou University, Guangzhou 510006, China"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2020,4,24]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"169","DOI":"10.1016\/S0921-8181(03)00023-7","article-title":"Anthropogenic sediment retention: Major global impact from registered river impoundments","volume":"39","author":"Meybeck","year":"2003","journal-title":"Glob. Planet. Chang."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"161","DOI":"10.1007\/s00027-014-0377-0","article-title":"A global boom in hydropower dam construction","volume":"77","author":"Zarfl","year":"2015","journal-title":"Aquat. Sci."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"128","DOI":"10.1126\/science.aac7082","article-title":"Balancing hydropower and biodiversity in the Amazon, Congo, and Mekong","volume":"351","author":"Winemiller","year":"2016","journal-title":"Science"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"363","DOI":"10.1038\/nature22333","article-title":"Damming the rivers of the Amazon Basin","volume":"546","author":"Latrubesse","year":"2017","journal-title":"Nature"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"456","DOI":"10.1126\/science.351.6272.456-b","article-title":"Tropical dams: To build or not to build?","volume":"351","author":"Fearnside","year":"2016","journal-title":"Science"},{"key":"ref_6","doi-asserted-by":"crossref","unstructured":"Biemans, H., Haddeland, I., Kabat, P., Ludwig, F., Hutjes, R., Heinke, J., Von Bloh, W., and Gerten, D. (2011). Impact of reservoirs on river discharge and irrigation water supply during the 20th century. Water Resour. Res., 47.","DOI":"10.1029\/2009WR008929"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"210","DOI":"10.1038\/nclimate1147","article-title":"Greenhouse\u2013gas emissions from energy use in the water sector","volume":"1","author":"Rothausen","year":"2011","journal-title":"Nat. Clim. Chang."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"215","DOI":"10.1038\/s41586-019-1111-9","article-title":"Mapping the world\u2019s free\u2013flowing rivers","volume":"569","author":"Grill","year":"2019","journal-title":"Nature"},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Bernardo, N., do Carmo, A., Park, E., and Alc\u00e2ntara, E. (2019). Retrieval of Suspended Particulate Matter in Inland Waters with Widely Differing Optical Properties Using a Semi\u2013Analytical Scheme. Remote Sens., 11.","DOI":"10.3390\/rs11192283"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"376","DOI":"10.1126\/science.1109454","article-title":"Impact of humans on the flux of terrestrial sediment to the global coastal ocean","volume":"308","author":"Syvitski","year":"2005","journal-title":"Science"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"403","DOI":"10.1130\/G45769.1","article-title":"A geomorphological assessment of wash\u2013load sediment fluxes and floodplain sediment sinks along the lower Amazon River","volume":"47","author":"Park","year":"2019","journal-title":"Geology"},{"key":"ref_12","doi-asserted-by":"crossref","unstructured":"Yang, Z.S., Wang, H.J., Saito, Y., Milliman, J.D., Xu, K., Qiao, S., and Shi, G. (2006). Dam impacts on the Changjiang (Yangtze) River sediment discharge to the sea: The past 55 years and after the Three Gorges Dam. Water Resour. Res., 42.","DOI":"10.1029\/2005WR003970"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"181","DOI":"10.1016\/j.geomorph.2010.03.018","article-title":"Basin\u2013wide sediment trapping efficiency of emerging reservoirs along the Mekong","volume":"119","author":"Kummu","year":"2010","journal-title":"Geomorphology"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"e1500323","DOI":"10.1126\/sciadv.1500323","article-title":"Four billion people facing severe water scarcity","volume":"2","author":"Mekonnen","year":"2016","journal-title":"Sci. Adv."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"15697","DOI":"10.1038\/ncomms15697","article-title":"Water scarcity hotspots travel downstream due to human interventions in the 20th and 21st century","volume":"8","author":"Veldkamp","year":"2017","journal-title":"Nat. Commun."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"8890","DOI":"10.1029\/2017WR022336","article-title":"Estimating the economic value of inter-annual reservoir storage in water resource systems","volume":"54","author":"Khadem","year":"2018","journal-title":"Water Resour. Res."},{"key":"ref_17","unstructured":"FAO, and WWC (2015). Towards a Water and Food Secure Future, in Critical Perspective for Policy\u2013Makers, W.W. COUNCIL."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"418","DOI":"10.1038\/nature20584","article-title":"High\u2013resolution mapping of global surface water and its long\u2013term changes","volume":"540","author":"Pekel","year":"2016","journal-title":"Nature"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"269","DOI":"10.1007\/s10712-016-9362-6","article-title":"Lake volume monitoring from space","volume":"37","author":"Arsen","year":"2016","journal-title":"Surv. Geophys."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"15829","DOI":"10.3402\/tellusa.v64i0.15829","article-title":"On the contribution of lakes in predicting near\u2013surface temperature in a global weather forecasting model","volume":"64","author":"Balsamo","year":"2012","journal-title":"Tellus A Dyn. Meteorol. Oceanogr."},{"key":"ref_21","doi-asserted-by":"crossref","unstructured":"Yang, X., Lu, X., Park, E., and Tarolli, P. (2019). Impacts of Climate Change on Lake Fluctuations in the Hindu Kush\u2013Himalaya\u2013Tibetan Plateau. Remote Sens., 11.","DOI":"10.3390\/rs11091082"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"403","DOI":"10.1016\/j.rse.2013.03.010","article-title":"Estimating water volume variations in lakes and reservoirs from four operational satellite altimetry databases and satellite imagery data","volume":"134","author":"Duan","year":"2013","journal-title":"Remote Sens. Environ."},{"key":"ref_23","doi-asserted-by":"crossref","unstructured":"Gao, H., Zhang, S., Durand, M., and Lee, H. (2016). Satellite Remote Sensing of Lakes and Wetlands. Hydrologic Remote Sensing, CRC Press.","DOI":"10.1201\/9781315370392-5"},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Alsdorf, D.E., Rodriguez, E., and Lettenmaier, D.P. (2007). Measuring surface water from space. Rev. Geophys., 45.","DOI":"10.1029\/2006RG000197"},{"key":"ref_25","first-page":"116","article-title":"Inferring elevation variation of lakes and reservoirs from areal extents: Calibrating with altimeter and in situ data","volume":"9","author":"May","year":"2018","journal-title":"Remote Sens. Appl. Soc. Environ."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"2553","DOI":"10.1080\/01431160600554397","article-title":"Remote sensing of water levels on floodplains: A spatial approach guided by hydraulic functioning","volume":"27","author":"Raclot","year":"2006","journal-title":"Int. J. Remote Sens."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"257","DOI":"10.1016\/j.jhydrol.2010.07.003","article-title":"Assimilation of spatially distributed water levels into a shallow\u2013water flood model. Part II: Use of a remote sensing image of Mosel River","volume":"390","author":"Hostache","year":"2010","journal-title":"J. Hydrol."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"651","DOI":"10.5194\/hess-17-651-2013","article-title":"Automated global water mapping based on wide\u2013swath orbital synthetic\u2013aperture radar","volume":"17","author":"Westerhoff","year":"2013","journal-title":"Hydrol. Earth Syst. Sci."},{"key":"ref_29","doi-asserted-by":"crossref","unstructured":"Huang, W., DeVries, B., Huang, C., Lang, M.W., Jones, J.W., Creed, I.F., and Carroll, M.L. (2018). Automated extraction of surface water extent from Sentinel\u20131 data. Remote Sens., 10.","DOI":"10.3390\/rs10050797"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"203","DOI":"10.1016\/j.isprsjprs.2014.07.014","article-title":"A fully automated TerraSAR\u2013X based flood service","volume":"104","author":"Martinis","year":"2015","journal-title":"ISPRS J. Photogramm. Remote Sens."},{"key":"ref_31","first-page":"11","article-title":"Determining water reservoir characteristics with global elevation data","volume":"43","author":"Mann","year":"2016","journal-title":"Geophys. Res. Lett."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"8052","DOI":"10.1002\/2016GL069560","article-title":"A novel algorithm for monitoring reservoirs under all-weather conditions at a high temporal resolution through passive microwave remote sensing","volume":"43","author":"Zhang","year":"2016","journal-title":"Geophys. Res. Lett."},{"key":"ref_33","doi-asserted-by":"crossref","unstructured":"Sheffield, J., Ferguson, C.R., Troy, T.J., Wood, E.F., and McCabe, M.F. (2009). Closing the terrestrial water budget from satellite remote sensing. Geophys. Res. Lett., 36.","DOI":"10.1029\/2009GL037338"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"687","DOI":"10.1016\/j.jenvman.2018.10.044","article-title":"Large lake gauging using fractional imagery","volume":"231","author":"Park","year":"2019","journal-title":"J. Environ. Manag."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"10676","DOI":"10.3390\/rs61110676","article-title":"Sentinel\u20131 for monitoring reservoirs: A performance analysis","volume":"6","author":"Amitrano","year":"2014","journal-title":"Remote Sens."},{"key":"ref_36","doi-asserted-by":"crossref","unstructured":"Chipman, J.W. (2019). A Multisensor Approach to Satellite Monitoring of Trends in Lake Area, Water Level, and Volume. Remote Sens., 11.","DOI":"10.3390\/rs11020158"},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"2349","DOI":"10.5194\/hess-15-2349-2011","article-title":"Assimilating SAR\u2013derived water level data into a hydraulic model: A case study","volume":"15","author":"Giustarini","year":"2011","journal-title":"Hydrol. Earth Syst. Sci."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"705","DOI":"10.1016\/j.rse.2012.06.017","article-title":"Automatic near real\u2013time selection of flood water levels from high resolution Synthetic Aperture Radar images for assimilation into hydraulic models: A case study","volume":"124","author":"Mason","year":"2012","journal-title":"Remote Sens. Environ."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"1715","DOI":"10.1109\/TGRS.2006.888103","article-title":"High\u2013resolution 3\u2013D flood information from radar imagery for flood hazard management","volume":"45","author":"Schumann","year":"2007","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"204","DOI":"10.1080\/01490419.2010.488983","article-title":"Investigating the performance of the Jason\u20132\/OSTM radar altimeter over lakes and reservoirs","volume":"33","author":"Birkett","year":"2010","journal-title":"Mar. Geod."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"5844","DOI":"10.1002\/2017GL072874","article-title":"A high-accuracy map of global terrain elevations","volume":"44","author":"Amazaki","year":"2017","journal-title":"Geophys. Res. Lett."},{"key":"ref_42","unstructured":"Jarvis, A., Reuter, H.I., Nelson, A., and Guevara, E. (2019, August 20). Hole\u2013Filled SRTM for the Globe Version 4. Available online: http:\/\/srtm.csi.cgiar.org\/."},{"key":"ref_43","doi-asserted-by":"crossref","unstructured":"Farr, T.G., Rosen, P.A., Caro, E., Crippen, R., Duren, R., Hensley, S., Kobrick, M., Paller, M., Rodriguez, E., and Roth, L. (2007). The shuttle radar topography mission. Rev. Geophys., 45.","DOI":"10.1029\/2005RG000183"},{"key":"ref_44","doi-asserted-by":"crossref","unstructured":"Simard, M., Pinto, N., Fisher, J.B., and Baccini, A. (2011). Mapping forest canopy height globally with spaceborne lidar. J. Geophys. Res. Biogeosci., 116.","DOI":"10.1029\/2011JG001708"},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"249","DOI":"10.14358\/PERS.72.3.249","article-title":"A global assessment of the SRTM performance","volume":"72","author":"Rodriguez","year":"2006","journal-title":"Photogramm. Eng. Remote Sens."},{"key":"ref_46","doi-asserted-by":"crossref","unstructured":"Birkett, C., Reynolds, C., Beckley, B., and Doorn, B. (2011). From research to operations: The USDA global reservoir and lake monitor. Coastal Altimetry, Springer.","DOI":"10.1007\/978-3-642-12796-0_2"},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"404","DOI":"10.1016\/j.rse.2003.04.001","article-title":"Dual\u2013season mapping of wetland inundation and vegetation for the central Amazon basin","volume":"87","author":"Hess","year":"2003","journal-title":"Remote Sens. Environ."},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"25179","DOI":"10.1029\/95JC02125","article-title":"The contribution of TOPEX\/POSEIDON to the global monitoring of climatically sensitive lakes","volume":"100","author":"Birkett","year":"1995","journal-title":"J. Geophys. Res. Oceans"},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"1733","DOI":"10.1016\/j.rse.2011.03.005","article-title":"Monitoring lake level changes on the Tibetan Plateau using ICESat altimetry data (2003\u20132009)","volume":"115","author":"Zhang","year":"2011","journal-title":"Remote Sens. Environ."},{"key":"ref_50","doi-asserted-by":"crossref","first-page":"061710","DOI":"10.1117\/1.JRS.6.061710","article-title":"Intercomparison and validation of continental water level products derived from satellite radar altimetry","volume":"6","author":"Ricko","year":"2012","journal-title":"J. Appl. Remote Sens."},{"key":"ref_51","doi-asserted-by":"crossref","unstructured":"Berry, P.A.M., Garlick, J.D., Mathers, E.L., and Freeman, J.A. (2005). Global inland water monitoring from multi-mission altimetry. Geophys. Res. Lett., 32.","DOI":"10.1029\/2005GL022814"},{"key":"ref_52","doi-asserted-by":"crossref","first-page":"25","DOI":"10.1016\/j.rse.2013.03.013","article-title":"Modeling and analysis of lake water storage changes on the Tibetan Plateau using multi\u2013mission satellite data","volume":"135","author":"Song","year":"2013","journal-title":"Remote Sens. Environ."},{"key":"ref_53","doi-asserted-by":"crossref","first-page":"400","DOI":"10.1016\/j.rse.2016.10.012","article-title":"Estimating water volume variations in Lake Victoria over the past 22 years using multi\u2013mission altimetry and remotely sensed images","volume":"187","author":"Tong","year":"2016","journal-title":"Remote Sens. Environ."},{"key":"ref_54","doi-asserted-by":"crossref","first-page":"31","DOI":"10.1016\/j.rse.2018.04.034","article-title":"Deriving daily water levels from satellite altimetry and land surface temperature for sparsely gauged catchments: A case study for the Mekong River","volume":"212","author":"Pham","year":"2018","journal-title":"Remote Sens. Environ."},{"key":"ref_55","doi-asserted-by":"crossref","first-page":"6396","DOI":"10.1002\/2014GL060641","article-title":"A global inventory of lakes based on high-resolution satellite imagery","volume":"41","author":"Verpoorter","year":"2014","journal-title":"Geophys. Res. Lett."},{"key":"ref_56","doi-asserted-by":"crossref","first-page":"91","DOI":"10.1002\/fee.1746","article-title":"Global proliferation of small hydropower plants\u2013science and policy","volume":"16","author":"Couto","year":"2018","journal-title":"Front. Ecol. Environ."},{"key":"ref_57","doi-asserted-by":"crossref","first-page":"935","DOI":"10.1016\/j.pce.2006.08.008","article-title":"Estimation of small reservoir storage capacities in Limpopo River Basin using geographical information systems (GIS) and remotely sensed surface areas: Case of Mzingwane catchment","volume":"31","author":"Sawunyama","year":"2006","journal-title":"Phys. Chem. Earth Parts A\/B\/C"},{"key":"ref_58","first-page":"1","article-title":"Small reservoirs depth\u2013area\u2013volume relationships in Savannah Regions of Brazil and Ghana","volume":"1","author":"Rodrigues","year":"2013","journal-title":"Water Resour. Irrig. Manag."},{"key":"ref_59","doi-asserted-by":"crossref","unstructured":"Gao, H., Birkett, C., and Lettenmaier, D.P. (2012). Global monitoring of large reservoir storage from satellite remote sensing. Water Resour. Res., 48.","DOI":"10.1029\/2012WR012063"},{"key":"ref_60","doi-asserted-by":"crossref","first-page":"96","DOI":"10.1016\/j.rse.2017.04.015","article-title":"Discharge estimation and forecasting by MODIS and altimetry data in Niger\u2013Benue River","volume":"195","author":"Tarpanelli","year":"2017","journal-title":"Remote Sens. Environ."},{"key":"ref_61","first-page":"52","article-title":"Volunteered Geographic Videos in Physical Geography: Data Mining from YouTube","volume":"108","author":"Lewis","year":"2018","journal-title":"Ann. Am. Assoc. Geogr."},{"key":"ref_62","doi-asserted-by":"crossref","first-page":"237","DOI":"10.1016\/j.jhydrol.2017.02.038","article-title":"Measuring water level in rivers and lakes from lightweight Unmanned Aerial Vehicles","volume":"548","author":"Bandini","year":"2017","journal-title":"J. Hydrol."},{"key":"ref_63","doi-asserted-by":"crossref","first-page":"111487","DOI":"10.1016\/j.rse.2019.111487","article-title":"Unmanned Aerial System (UAS) observations of water surface elevation in a small stream: Comparison of radar altimetry, LIDAR and photogrammetry techniques","volume":"237","author":"Bandini","year":"2020","journal-title":"Remote Sens. Environ."},{"key":"ref_64","doi-asserted-by":"crossref","first-page":"307","DOI":"10.1007\/s10712-015-9346-y","article-title":"The SWOT mission and its capabilities for land hydrology","volume":"37","author":"Biancamaria","year":"2016","journal-title":"Surv. Geophys."},{"key":"ref_65","doi-asserted-by":"crossref","first-page":"617","DOI":"10.1038\/s41893-018-0159-0","article-title":"Water shortages worsened by reservoir effects","volume":"1","author":"Wanders","year":"2018","journal-title":"Nat. Sustain."}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/12\/8\/1353\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,13]],"date-time":"2025-10-13T14:27:11Z","timestamp":1760365631000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/12\/8\/1353"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2020,4,24]]},"references-count":65,"journal-issue":{"issue":"8","published-online":{"date-parts":[[2020,4]]}},"alternative-id":["rs12081353"],"URL":"https:\/\/doi.org\/10.3390\/rs12081353","relation":{},"ISSN":["2072-4292"],"issn-type":[{"value":"2072-4292","type":"electronic"}],"subject":[],"published":{"date-parts":[[2020,4,24]]}}}