{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,19]],"date-time":"2026-04-19T08:13:43Z","timestamp":1776586423637,"version":"3.51.2"},"reference-count":27,"publisher":"MDPI AG","issue":"15","license":[{"start":{"date-parts":[[2019,8,1]],"date-time":"2019-08-01T00:00:00Z","timestamp":1564617600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>To improve the accuracy of analysis outputs from remotely sensed images, shadow and illumination effects need to be minimised or removed. Shadow behaviour at different spectral wavelengths needs to be understood to quantify shadow accurately. This study examined whether a normalised spectral signature of shadow is invariant to sun\u2013object\u2013sensor geometry and can be used to quantify shadow depth. A \u201cFieldSpec\u00ae Pro FR\u201d Spectroradiometer and a Canon 450D digital SLR camera were used to measure signatures of cast shadow. Our field-based experiment used an occulter to cast shadow onto a \u2018Spectralon\u2019 white plate at six incremental zenith angles and evaluated shadow behaviour within and between varying footprints. A white-balanced image of each shadow zenith was taken by the Canon 450D. The FR Spectroradiometer signatures were normalised to unit vector form and compared to longitudinal transect profiles of shadow from normalised camera images using a scattering index (SI). The normalised signatures show that shadow depth is darker and more \u2018blue\u2019 at the proximal areas and conversely that image brightness values increases towards distal areas. Since image brightness is a result of sun\u2013object\u2013sensor geometry, we conclude that a normalised spectral signature is invariant to geometry and can be used to quantify shadow depth.<\/jats:p>","DOI":"10.3390\/rs11151806","type":"journal-article","created":{"date-parts":[[2019,8,1]],"date-time":"2019-08-01T11:39:37Z","timestamp":1564659577000},"page":"1806","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":2,"title":["The Depths of Cast Shadow"],"prefix":"10.3390","volume":"11","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-4955-0228","authenticated-orcid":false,"given":"Mark","family":"Cameron","sequence":"first","affiliation":[{"name":"Ecosystem Management, School of Environmental and Rural Science, University of New England, Armidale, NSW 2351, Australia"},{"name":"NSW Office of Environment &amp; Heritage, Coffs Harbour, NSW 2450, Australia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9205-756X","authenticated-orcid":false,"given":"Lalit","family":"Kumar","sequence":"additional","affiliation":[{"name":"Ecosystem Management, School of Environmental and Rural Science, University of New England, Armidale, NSW 2351, Australia"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2019,8,1]]},"reference":[{"key":"ref_1","unstructured":"Li, F., Jupp, D., and Thankappan, M. (2011, January 12\u201316). Using high resolution DSM data to correct the terrain illumination effect in Landsat data. Proceedings of the 19th International Congress on Modelling and Simulation, Perth, Australia."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"83","DOI":"10.3390\/rs5010083","article-title":"An operational scheme for deriving standardised surface reflectance from Landsat TM\/ETM+ and SPOT HRG imagery for eastern Australia","volume":"5","author":"Flood","year":"2013","journal-title":"Remote Sens."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"2618","DOI":"10.1109\/36.789656","article-title":"Correction of the topographic effect in remote sensing","volume":"37","author":"Dymond","year":"1999","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"403","DOI":"10.1007\/s11769-013-0613-x","article-title":"Review of shadow detection and de-shadowing methods in remote sensing","volume":"23","author":"Shahtahmassebi","year":"2013","journal-title":"Chin. Geograph. Sci."},{"key":"ref_5","doi-asserted-by":"crossref","unstructured":"Adler-Golden, S.M., Matthew, M.W., Anderson, G.P., Felde, G.W., and Gardner, J.A. (2002). Algorithm for De-Shadowing Spectral Imagery. International Symposium on Optical Science and Technology, International Society for Optics and Photonics.","DOI":"10.1117\/12.451691"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"3137","DOI":"10.1080\/01431160500114664","article-title":"De-shadowing of satellite\/airborne imagery","volume":"26","author":"Richter","year":"2005","journal-title":"Int. J. Remote Sens."},{"key":"ref_7","doi-asserted-by":"crossref","unstructured":"Cameron, M., and Kumar, L. (2018). Diffuse skylight as a surrogate for shadow detection in high-resolution imagery acquired under clear sky conditions. Remote Sens., 10.","DOI":"10.3390\/rs10081185"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"21","DOI":"10.1016\/j.isprsjprs.2013.02.003","article-title":"Shadow detection in very high spatial resolution aerial images: A comparative study","volume":"80","author":"Adeline","year":"2013","journal-title":"ISPRS J. Photogramm. Remote Sens."},{"key":"ref_9","unstructured":"Drew, M.S., Finlayson, G.D., and Hordley, S.D. (2003, January 12). Recovery of chromaticity image free from shadows via illumination invariance. Proceedings of the IEEE Workshop on Color and Photometric Methods in Computer Vision (ICCV\u201903), Nice, France."},{"key":"ref_10","unstructured":"Funka-Lea, G., and Bajcsy, R. (1995, January 20\u201323). In Combining color and geometry for the active, visual recognition of shadows. Proceedings of the Fifth International Conference on Computer Vision, Cambridge, MA, USA."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"1945","DOI":"10.1080\/01431160701395302","article-title":"Shadow detection in colour high-resolution satellite images","volume":"29","author":"Ambrosio","year":"2008","journal-title":"Int. J. Remote Sens."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"169","DOI":"10.14358\/PERS.71.2.169","article-title":"Shadow analysis in high-resolution satellite imagery of urban areas","volume":"71","author":"Dare","year":"2005","journal-title":"Photogramm. Eng. Remote Sens."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"B154","DOI":"10.1364\/AO.54.00B154","article-title":"Shadows","volume":"54","author":"Lynch","year":"2015","journal-title":"Appl. Opt."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"195","DOI":"10.1016\/0146-664X(79)90001-7","article-title":"Region extraction and shape analysis in aerial photographs","volume":"10","author":"Nagao","year":"1979","journal-title":"Comput. Graph. Image Proc."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1117\/12.543794","article-title":"The sequential maximum angle convex cone (SMACC) endmember model","volume":"5425","author":"Gruninger","year":"2004","journal-title":"Algorithms and Technologies for Multispectral, Hyperspectral, and Ultraspectral Imagery X"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"257","DOI":"10.1109\/JSTARS.2010.2042281","article-title":"An evaluation of the use of atmospheric and BRDF correction to standardize Landsat data","volume":"3","author":"Li","year":"2010","journal-title":"IEEE J. Sel. Top. Appl. Earth Obs. Remote Sens."},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Wen, J., Liu, Q., Xiao, Q., Liu, Q., You, D., Hao, D., Wu, S., and Lin, X. (2018). Characterizing land surface anisotropic reflectance over rugged terrain: A review of concepts and recent developments. Remote Sens., 10.","DOI":"10.3390\/rs10030370"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"S212","DOI":"10.1088\/0026-1394\/40\/1\/349","article-title":"Degradation of the diffuse reflectance of Spectralon under low-level irradiation","volume":"40","author":"Nikolaus","year":"2003","journal-title":"Metrologia"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"1117","DOI":"10.1109\/JSTARS.2016.2593984","article-title":"Field and airborne spectroscopy cross validation\u2014Some considerations","volume":"10","author":"Hueni","year":"2016","journal-title":"IEEE J. Sel. Topics Appl. Earth Obs. Remote Sens."},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Deadman, A., Behnert, I., Fox, N.P., and Griffith, D. (2011, January 24\u201329). Laboratory panel and radiometer calibration. Proceedings of the IEEE International Geoscience and Remote Sensing Symposium, Vancouver, BC, Canada.","DOI":"10.1109\/IGARSS.2011.6050079"},{"key":"ref_21","unstructured":"Malthus, T., and MacLellan, C. (2010, January 23\u201325). High performance fore optic accessories and tools for reflectance and radiometric measurements with the ASD FR3 spectroradiometer. Proceedings of the Art, Science and Applications of Reflectance Spectroscopy Scientific Symposium, Boulder, CO, USA."},{"key":"ref_22","unstructured":"Schl\u00e4pfer, D., Richter, R., and Damm, A. (2013, January 8\u201310). Correction of shadowing in imaging spectroscopy data by quantification of the proportion of diffuse illumination. Proceedings of the 8th SIG-IS EARSeL Imaging Spectroscopy Workshop, Nantes, France."},{"key":"ref_23","unstructured":"Avery, T.E., and Berlin, G.L. (1992). Fundamentals of Remote Sensing and Airphoto Interpretation, Macmillan Publishing Company. [5th ed.]."},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Jensen, J.R., and Lulla, K. (1987). Introductory Digital Image Processing: A Remote Sensing Perspective, Prentice Hall.","DOI":"10.1080\/10106048709354084"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"431","DOI":"10.1137\/0111030","article-title":"An algorithm for least-squares estimation of nonlinear parameters","volume":"11","author":"Marquardt","year":"1963","journal-title":"J. Soc. Ind. Appl. Math."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"3503","DOI":"10.1080\/01431160210154029","article-title":"Correcting satellite imagery for the variance of reflectance and illumination with topography","volume":"24","author":"Shepherd","year":"2003","journal-title":"Int. J. Remote Sens."},{"key":"ref_27","doi-asserted-by":"crossref","unstructured":"Schl\u00e4pfer, D., Hueni, A., and Richter, R. (2018). Cast Shadow Detection to Quantify the Aerosol Optical Thickness for Atmospheric Correction of High Spatial Resolution Optical Imagery. Remote Sens., 10.","DOI":"10.3390\/rs10020200"}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/11\/15\/1806\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T13:12:21Z","timestamp":1760188341000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/11\/15\/1806"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2019,8,1]]},"references-count":27,"journal-issue":{"issue":"15","published-online":{"date-parts":[[2019,8]]}},"alternative-id":["rs11151806"],"URL":"https:\/\/doi.org\/10.3390\/rs11151806","relation":{},"ISSN":["2072-4292"],"issn-type":[{"value":"2072-4292","type":"electronic"}],"subject":[],"published":{"date-parts":[[2019,8,1]]}}}