{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,22]],"date-time":"2026-09-22T10:36:49Z","timestamp":1790073409397,"version":"4.0.1"},"reference-count":62,"publisher":"MDPI AG","issue":"10","license":[{"start":{"date-parts":[[2020,5,15]],"date-time":"2020-05-15T00:00:00Z","timestamp":1589500800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"NSW Office of the Premier","award":["NA"],"award-info":[{"award-number":["NA"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>Rapid and widespread monitoring of inland and coastal water quality occurs through the use of remote sensing and near-surface water quality sensors. A new addition is the development of smartphone applications (Apps) to measure and record surface reflectance, water color and water quality parameters. In this paper, we present a field study of the HydroColor (HC, measures RGB reflectance and suspended particulate matter (SPM)) and EyeOnWater (EoW, determines the Forel\u2013Ule scale\u2014an indication to the visual appearance of the water surface) smartphone Apps to evaluate water quality for inland waters in Eastern Australia. The Brisbane river, multiple lakes and reservoirs and lagoons in Queensland and New South Wales were visited; hyperspectral reflection spectra were collected and water samples were analysed in the laboratory as reference. Based on detailed measurements at 32 sites, covering inland waters with a large range in sediment and algal concentrations, we find that both water quality Apps are close, but not quite on par with scientific spectrometers. EoW is a robust application that manages to capture the color of water with accuracy and precision. HC has great potential, but is influenced by errors in the observational procedure and errors in the processing of images in the iPhone. The results show that repeated observations help to reduce the effects of outliers, while implementation of camera response functions and processing should help to reduce systematic errors. For both Apps, no universal conversion to water quality composition is established, and we conclude that: (1) replicated measurements are useful; (2) color is a reliable monitoring parameter in its own right but it should not be used for other water quality variables, and; (3) tailored algorithms to convert reflectance and color to composition could be developed for lakes individually.<\/jats:p>","DOI":"10.3390\/rs12101578","type":"journal-article","created":{"date-parts":[[2020,5,15]],"date-time":"2020-05-15T10:53:59Z","timestamp":1589540039000},"page":"1578","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":55,"title":["An Evaluation of Citizen Science Smartphone Apps for Inland Water Quality Assessment"],"prefix":"10.3390","volume":"12","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-7161-8770","authenticated-orcid":false,"given":"Tim J.","family":"Malthus","sequence":"first","affiliation":[{"name":"Coastal Sensing and Modelling Group, Coasts Program, CSIRO Oceans and Atmosphere, Ecosciences Precinct, 41 Boggo Road, Dutton Park, QLD 4102, Australia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Renee","family":"Ohmsen","sequence":"additional","affiliation":[{"name":"School of Earth and Environmental Sciences, University of Queensland, St Lucia, QLD 4072, Australia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8901-7567","authenticated-orcid":false,"given":"Hendrik J. van der","family":"Woerd","sequence":"additional","affiliation":[{"name":"Institute for Environmental Studies (IVM), VU University Amsterdam, De Boelelaan 1111, 1081 HV Amsterdam, The Netherlands"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2020,5,15]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"173","DOI":"10.1016\/j.jhydrol.2010.03.019","article-title":"A statistical approach for the rationalization of water quality indicators in surface water quality monitoring networks. 2010","volume":"386","author":"Khalil","year":"2010","journal-title":"J. Hydrol."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"27","DOI":"10.1111\/j.1758-2229.2008.00004.x","article-title":"Climate change: A catalyst for global expansion of harmful cyanobacterial blooms","volume":"1","author":"Paerl","year":"2009","journal-title":"Environ. Microbiol. Rep."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"922","DOI":"10.1038\/s41893-019-0390-3","article-title":"Citizen Science and the United Nations Sustainable Development Goals","volume":"2","author":"Fritz","year":"2019","journal-title":"Nat. Sustain."},{"key":"ref_4","unstructured":"Dekker, A.G. (1993). Detection of Optical Water Quality Parameters for Eutrophic Waters by High Resolution Remote Sensing. [Ph.D. Thesis, Vrije University]."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"254","DOI":"10.1016\/j.rse.2012.11.023","article-title":"Airborne hyperspectral remote sensing to assess spatial distribution of water quality characteristics in large rivers: The Mississippi River and its tributaries in Minnesota","volume":"130","author":"Olmanson","year":"2013","journal-title":"Remote Sens. Environ."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"181","DOI":"10.1016\/j.rse.2015.05.023","article-title":"Measuring freshwater aquatic ecosystems: The need for a hyperspectral global mapping satellite mission","volume":"167","author":"Hestir","year":"2015","journal-title":"Remote Sens. Environ."},{"key":"ref_7","unstructured":"Busch, J.A., Zielinski, O., and Cembella, A.D. (2013). Subsea Optics and Imaging. Subsea Optics and Imaging, Elsevier."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"5189","DOI":"10.1021\/es0012669","article-title":"Optical teledetection of chlorophyll a in estuarine and coastal waters","volume":"34","author":"Gons","year":"2000","journal-title":"Environ. Sci. Technol."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"45003","DOI":"10.1088\/1748-9326\/4\/4\/045003","article-title":"A bio-optical algorithm for the remote estimation of the chlorophyll- a concentration in case 2 waters","volume":"4","author":"Gitelson","year":"2009","journal-title":"Environ. Res. Lett."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"6855","DOI":"10.1080\/01431161.2010.512947","article-title":"A current review of empirical procedures of remote sensing in inland and near-coastal transitional waters","volume":"32","author":"Matthews","year":"2011","journal-title":"Int. J. Remote Sens."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"15","DOI":"10.1080\/01431160010006917","article-title":"Analytical algorithms for lake water TSM estimation for retrospective analyses of TM and SPOT sensor data","volume":"23","author":"Dekker","year":"2002","journal-title":"Int. J. Remote Sens."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"854","DOI":"10.1016\/j.rse.2009.11.022","article-title":"Calibration and validation of a generic multisensor algorithm for mapping of total suspended matter in turbid waters","volume":"114","author":"Nechad","year":"2010","journal-title":"Remote Sens. Environ."},{"key":"ref_13","doi-asserted-by":"crossref","unstructured":"Al-Kharusi, E.S., Tenenbaum, D.E., Abdi, A.M., Kutser, T., Karlsson, J., Bergstr\u00f6m, A.-K., and Berggren, M. (2020). Large-Scale Retrieval of Coloured Dissolved Organic Matter in Northern Lakes Using Sentinel-2 Data. Remote Sens., 12.","DOI":"10.3390\/rs12010157"},{"key":"ref_14","unstructured":"Dekker, A., and Hestir, E. (2012). Evaluating the Feasibility of Systematic Inland Water Quality Monitoring with Satellite Remote Sensing."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"63615","DOI":"10.1117\/1.JRS.6.063615","article-title":"Intercomparison in the field between the new WISP-3 and other radiometers (TriOS Ramses, ASD FieldSpec, and TACCS)","volume":"6","author":"Hommersom","year":"2012","journal-title":"J. Appl. Remote Sens."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"2705","DOI":"10.1016\/j.rse.2010.06.006","article-title":"Hyperspectral remote sensing of cyanobacterial pigments as indicators for cell populations and toxins in eutrophic lakes","volume":"114","author":"Hunter","year":"2010","journal-title":"Remote Sens. Environ."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"4147","DOI":"10.1080\/01431161003789549","article-title":"Using hyperspectral remote sensing to estimate chlorophyll- a and phycocyanin in a mesotrophic reservoir","volume":"31","author":"Li","year":"2010","journal-title":"Int. J. Remote Sens."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"725","DOI":"10.1016\/j.rse.2010.10.014","article-title":"Remote estimation of chlorophyll a in optically complex waters based on optical classification","volume":"115","author":"Le","year":"2011","journal-title":"Remote Sens. Environ."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"137","DOI":"10.1016\/j.jglr.2013.06.016","article-title":"Remote sensing reflectance in the Great Lakes: In situ measurements, closure analyses, and a forward model","volume":"39","author":"Effler","year":"2013","journal-title":"J. Great Lakes Res."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"196","DOI":"10.1016\/j.rse.2015.01.025","article-title":"Application of hyperspectral remote sensing to cyanobacterial blooms in inland waters","volume":"167","author":"Kudela","year":"2015","journal-title":"Remote Sens. Environ."},{"key":"ref_21","doi-asserted-by":"crossref","unstructured":"Busch, J.A., Badaj\u00ed, R., Ceccaroni, L., Friedrichs, A., Piera, J., Simon, C., Thijsse, P., Wernand, M., Van der Woerd, H.J., and Zielinski, O. (2016). Citizen bio-optical observations from coast- and ocean and their compatibility with ocean colour satellite measurements. Remote Sens., 8.","DOI":"10.3390\/rs8110879"},{"key":"ref_22","doi-asserted-by":"crossref","unstructured":"Brando, V.E., Lovell, J.L., King, E.A., Boadle, D., Scott, R., and Schroeder, T. (2016). The Potential of Autonomous Ship-Borne Hyperspectral Radiometers for the Validation of Ocean Color Radiometry Data. Remote Sens.","DOI":"10.3390\/rs8020150"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"108","DOI":"10.1016\/j.rse.2016.04.011","article-title":"Landsat 8: Providing continuity and increased precision for measuring multi-decadal time series of total suspended matter","volume":"185","author":"Lymburner","year":"2016","journal-title":"Remote Sens. Environ."},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Malthus, T.J., Lehmann, E., Ho, X., Botha, E., and Anstee, J. (2019). Implementation of a satellite based inland water algal bloom alerting system using analysis ready data. Remote Sens., 11.","DOI":"10.3390\/rs11242954"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"477","DOI":"10.5194\/os-9-477-2013","article-title":"MERIS-based ocean colour classification with the discrete Forel-Ule scale","volume":"9","author":"Wernand","year":"2013","journal-title":"Ocean Sci."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"25663","DOI":"10.3390\/s151025663","article-title":"True colour classification of natural waters with medium-spectral resolution satellites: SeaWiFS, MODIS, MERIS and OLCI","volume":"15","author":"Wernand","year":"2015","journal-title":"Sensors"},{"key":"ref_27","doi-asserted-by":"crossref","unstructured":"Van der Woerd, H.J., and Wernand, M.R. (2018). Hue angle product for low to medium spectral resolution optical satellite sensors. Remote Sens., 10.","DOI":"10.3390\/rs10020180"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"444","DOI":"10.1016\/j.rse.2018.08.026","article-title":"Trophic state assessment of global inland waters using a MODIS-derived Forel-Ule index","volume":"217","author":"Wang","year":"2018","journal-title":"Remote Sens. Environ."},{"key":"ref_29","doi-asserted-by":"crossref","unstructured":"Lehmann, M.K., Nguyen, U., Allan, M., and Van der Woerd, H.J. (2018). Colour classification of 1486 lakes across a wide range of optical water types. Remote Sens., 10.","DOI":"10.3390\/rs10081273"},{"key":"ref_30","doi-asserted-by":"crossref","unstructured":"Giardino, C., Koks, K., Bolpagni, R., Luciani, G., Candiani, G., Lehmann, M.K., Van der Woerd, H.J., and Bresciani, M. (2019). The color of water from space: A case study for Italian lakes from Sentinel-2. Earth Observation and Geospatial Analysis, Intech Open.","DOI":"10.5772\/intechopen.86596"},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"697","DOI":"10.1002\/lom3.10059","article-title":"WACODI: A generic algorithm to derive the intrinsic color of natural waters from digital images","volume":"13","author":"Novoa","year":"2015","journal-title":"Limnol. Oceanogr. Methods"},{"key":"ref_32","doi-asserted-by":"crossref","unstructured":"Leeuw, T., and Boss, E. (2018). The HydroColor App: Above water measurements of remote sensing reflectance and turbidity using a smartphone camera. Sensors, 18.","DOI":"10.3390\/s18010256"},{"key":"ref_33","doi-asserted-by":"crossref","unstructured":"Yang, Y., Cowen, L.L.E., and Costa, M. (2018). Is ocean reflectance acquired by citizen scientists robust for science applications?. Remote Sens., 10.","DOI":"10.3390\/rs10060835"},{"key":"ref_34","doi-asserted-by":"crossref","unstructured":"Ouma, Y.O., Waga, J., Okech, O., Lavisa, O., and Mbuthia, D. (2018). Estimation of reservoir bio-optical water quality parameters using smartphone sensor apps and Landsat ETM+: Review and comparative experimental results. J. Sens., 3490757.","DOI":"10.1155\/2018\/3490757"},{"key":"ref_35","unstructured":"Fargoin, G.S., and Mueller, J.L. (2002). Ocean Optics Protocols for Satellite Ocean Color Sensor Validation."},{"key":"ref_36","unstructured":"Tilstone, G.H., Moore, G.F., Doerffer, R., R\u00f8ttgers, R., Ruddick, K.G., Pasterkamp, R., and J\u00f8rgensen, P.V. (2003, January 20\u201324). Regional Validation of MERIS Chlorophyll products in North Sea REVAMP Protocols. Proceedings of the Working Meeting on MERIS and AATSR Calibration and Geophysical Validation (ENVISAT MAVT-2003), Frascati, Rome, Italy."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"31611","DOI":"10.1029\/2000JC000359","article-title":"Optical properties of waters in the Australasian sector of the Southern Ocean","volume":"106","author":"Clementson","year":"2001","journal-title":"J. Geophys. Res. Oceans"},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"3200","DOI":"10.1364\/OE.28.003200","article-title":"On the equivalence of near-surface methods to determine the water-leaving radiance","volume":"28","author":"Zibordi","year":"2020","journal-title":"Opt. Express"},{"key":"ref_39","doi-asserted-by":"crossref","unstructured":"Ruddick, K.G., Vos, K., Boss, E., Castagna, A., Frouin, R., Gilerson, A., Hieronymi, M., Johnson, B.C., Kuusk, J., and Lee, Z. (2019). A Review of Protocols for Fiducial Reference Measurements of Water-Leaving Radiance for Validation of Satellite Remote-Sensing Data over Water. Remote Sens., 11.","DOI":"10.3390\/rs11192198"},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"237","DOI":"10.4319\/lo.2005.50.1.0237","article-title":"Remote sensing of the cyanobacterial pigment phycocyanin in turbid inland water","volume":"50","author":"Simis","year":"2005","journal-title":"Limnol. Oceanogr."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"3996","DOI":"10.1016\/j.rse.2007.11.019","article-title":"An evaluation of algorithms for the remote sensing of cyanobacterial biomass","volume":"112","author":"Simis","year":"2008","journal-title":"Remote Sens. Environ."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"3582","DOI":"10.1016\/j.rse.2008.04.015","article-title":"A simple semi-analytical model for remote estimation of chlorophyll-a in turbid waters-Validation","volume":"112","author":"Gitelson","year":"2008","journal-title":"Remote Sens. Environ."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"9","DOI":"10.1016\/j.rse.2014.06.009","article-title":"Remote sensing of freshwater cyanobacteria: An extended IOP Inversion Model of Inland Waters (IIMIW) for partitioning absorption coefficient and estimating phycocyanin","volume":"157","author":"Li","year":"2015","journal-title":"Remote Sens. Environ."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"111648","DOI":"10.1016\/j.rse.2020.111648","article-title":"An OLCI-based algorithm for semi-empirically partitioning absorption coefficient and estimating chlorophyll a concentration in various turbid case-2 waters","volume":"239","author":"Liu","year":"2020","journal-title":"Remote Sens. Environ."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"4774","DOI":"10.3390\/rs5104774","article-title":"A Performance Review of Reflectance Based Algorithms for Predicting Phycocyanin Concentrations in Inland Waters","volume":"5","author":"Ogashawara","year":"2013","journal-title":"Remote Sens."},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"846","DOI":"10.1002\/lno.10674","article-title":"Optical types of inland and coastal waters","volume":"63","author":"Spyrakos","year":"2017","journal-title":"Limnol. Oceanogr."},{"key":"ref_47","doi-asserted-by":"crossref","unstructured":"Kirk, J.T. (2011). Light and Photosynthesis in Aquatic Ecosystems, Cambridge University Press. [3rd ed.].","DOI":"10.1017\/CBO9781139168212"},{"key":"ref_48","unstructured":"CIE (1932). Commission Internationale de l\u2019\u00c9clairage Proceedings, 1931, Cambridge University Press."},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"13057","DOI":"10.2971\/jeos.2013.13057","article-title":"The Forel-Ule scale revisited spectrally: Preparation protocols, transmission measurements and chromaticity","volume":"8","author":"Novoa","year":"2013","journal-title":"J. Eur. Opt. Soc. RP"},{"key":"ref_50","unstructured":"Leeuw, T. (2014). Crowdsourcing Water Quality Data Using the iPhone Camera, University of Maine. Available online: http:\/\/digitalcommons.library.umaine.edu\/etd\/2118."},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"3602","DOI":"10.1364\/AO.54.003602","article-title":"Modern approaches to shipborne ocean color remote sensing","volume":"54","author":"Garaba","year":"2015","journal-title":"Appl. Opt."},{"key":"ref_52","unstructured":"Mueller, J.L., Fargion, G.S., Mcclain, C.R., Mueller, J.L., Morel, A., Frouin, R., Davis, C., Arnone, R., Carder, K., and Steword, R.G. (2003). NASA\/TM-2003-Ocean Optics Protocols for Satellite Ocean Color Sensor Validation, Revision 4, Volume III: Radiometric Measurements and Data Analysis Protocols."},{"key":"ref_53","doi-asserted-by":"crossref","first-page":"7442","DOI":"10.1364\/AO.38.007442","article-title":"Estimation of the remote-sensing reflectance from above-surface measurements","volume":"38","author":"Mobley","year":"1999","journal-title":"Appl. Opt."},{"key":"ref_54","unstructured":"Pascale, D. (2020, January 24). A review of RGB color spaces... from xyY to R\u2019G\u2019B\u2019. Available online: www.babelcolor.com."},{"key":"ref_55","unstructured":"Lindell, L.T., Pierson, D., Premazzi, G., and Zillioli, E. (1999). Manual for Monitoring European Lakes Using Remote Sensing Techniques, Joint Research Centre European Commission."},{"key":"ref_56","doi-asserted-by":"crossref","first-page":"44","DOI":"10.5589\/m03-051","article-title":"Mapping of the North Sea turbid coastal waters using SeaWiFS data","volume":"30","author":"Pasterkamp","year":"2004","journal-title":"Can. J. Remote Sens."},{"key":"ref_57","doi-asserted-by":"crossref","first-page":"111249","DOI":"10.1016\/j.rse.2019.111249","article-title":"Optical properties of Forel-Ule water types deduced from 15 years of global satellite ocean color observations","volume":"231","author":"Pitarch","year":"2018","journal-title":"Remote Sens. Environ."},{"key":"ref_58","unstructured":"Malthus, T.J., Lehmann, E., Ho, X., Gensemer, S., Anstee, J., Botha, E., Brayan, J., Bowling, L., Shaikh, M., and Ohmsen, R. (2017, January 16\u201318). An algal bloom early warning system for NSW using satellite and near-surface observations. Proceedings of the OzWater17 Conference, Available online: https:\/\/awa.sharefile.com\/share?#\/view\/s69fcd4a5d344354b."},{"key":"ref_59","doi-asserted-by":"crossref","first-page":"495","DOI":"10.1007\/s10661-017-6205-y","article-title":"An evaluation of a handheld spectroradiometer for the near real-time measurement of cyanobacteria for bloom management purposes","volume":"189","author":"Bowling","year":"2017","journal-title":"Environ. Monit. Assess."},{"key":"ref_60","doi-asserted-by":"crossref","first-page":"137","DOI":"10.1007\/s10708-008-9188-y","article-title":"The credibility of volunteered geographic information","volume":"72","author":"Flanagin","year":"2008","journal-title":"GeoJournal"},{"key":"ref_61","doi-asserted-by":"crossref","unstructured":"Wernand, M.R., Van der Woerd, H.J., and Gieskes, W.W.C. (2013). Trends in Ocean Colour and Chlorophyll Concentration from 1889 to 2000, Worldwide. PLoS ONE.","DOI":"10.1371\/journal.pone.0063766"},{"key":"ref_62","doi-asserted-by":"crossref","unstructured":"Burggraaff, O., Schmidt, N., Zamorano, J., Puly, K., Pascual, S., Tapia, C., Spyrakos, E., and Snik, F. (2019). Standardized spectral and radiometric calibration of consumer cameras. Opt. Express., 19075.","DOI":"10.1364\/OE.27.019075"}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/12\/10\/1578\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T09:29:17Z","timestamp":1760174957000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/12\/10\/1578"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2020,5,15]]},"references-count":62,"journal-issue":{"issue":"10","published-online":{"date-parts":[[2020,5]]}},"alternative-id":["rs12101578"],"URL":"https:\/\/doi.org\/10.3390\/rs12101578","relation":{},"ISSN":["2072-4292"],"issn-type":[{"value":"2072-4292","type":"electronic"}],"subject":[],"published":{"date-parts":[[2020,5,15]]}}}