{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,12]],"date-time":"2026-02-12T15:53:01Z","timestamp":1770911581011,"version":"3.50.1"},"reference-count":58,"publisher":"MDPI AG","issue":"7","license":[{"start":{"date-parts":[[2017,7,14]],"date-time":"2017-07-14T00:00:00Z","timestamp":1499990400000},"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>The future German Environmental Mapping and Analysis Program (EnMAP) mission, due to launch in late 2019, will deliver high resolution hyperspectral data from space and will thus contribute to a better monitoring of the dynamic surface of the earth. Exploiting the satellite\u2019s \u00b130\u00b0 across-track pointing capabilities will allow for the collection of hyperspectral time-series of homogeneous quality. Various studies have shown the possibility to retrieve geo-biophysical plant variables, like leaf area index (LAI) or leaf chlorophyll content (LCC), from narrowband observations with fixed viewing geometry by inversion of radiative transfer models (RTM). In this study we assess the capability of the well-known PROSPECT 5B + 4SAIL (Scattering by Arbitrarily Inclined Leaves) RTM to estimate these variables from off-nadir observations obtained during a field campaign with respect to EnMAP-like sun\u2013target\u2013sensor-geometries. A novel approach for multiple inquiries of a large look-up-table (LUT) in hierarchical steps is introduced that accounts for the varying instances of all variables of interest. Results show that anisotropic effects are strongest for early growth stages of the winter wheat canopy which influences also the retrieval of the variables. RTM inversions from off-nadir spectra lead to a decreased accuracy for the retrieval of LAI with a relative root mean squared error (rRMSE) of 18% at nadir vs. 25% (backscatter) and 24% (forward scatter) at off-nadir. For LCC estimations, however, off-nadir observations yield improvements, i.e., rRMSE (nadir) = 24% vs. rRMSE (forward scatter) = 20%. It follows that for a variable retrieval through RTM inversion, the final user will benefit from EnMAP time-series for biophysical studies regardless of the acquisition angle and will thus be able to exploit the maximum revisit capability of the mission.<\/jats:p>","DOI":"10.3390\/rs9070726","type":"journal-article","created":{"date-parts":[[2017,7,14]],"date-time":"2017-07-14T10:45:02Z","timestamp":1500029102000},"page":"726","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":63,"title":["Retrieval of Biophysical Crop Variables from Multi-Angular Canopy Spectroscopy"],"prefix":"10.3390","volume":"9","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-8911-9064","authenticated-orcid":false,"given":"Martin","family":"Danner","sequence":"first","affiliation":[{"name":"Department of Geography, Ludwig-Maximilians-Universit\u00e4t M\u00fcnchen, Luisenstra\u00dfe 37, D-80333 Munich, Germany"}]},{"given":"Katja","family":"Berger","sequence":"additional","affiliation":[{"name":"Department of Geography, Ludwig-Maximilians-Universit\u00e4t M\u00fcnchen, Luisenstra\u00dfe 37, D-80333 Munich, Germany"}]},{"given":"Matthias","family":"Wocher","sequence":"additional","affiliation":[{"name":"Department of Geography, Ludwig-Maximilians-Universit\u00e4t M\u00fcnchen, Luisenstra\u00dfe 37, D-80333 Munich, Germany"}]},{"given":"Wolfram","family":"Mauser","sequence":"additional","affiliation":[{"name":"Department of Geography, Ludwig-Maximilians-Universit\u00e4t M\u00fcnchen, Luisenstra\u00dfe 37, D-80333 Munich, Germany"}]},{"given":"Tobias","family":"Hank","sequence":"additional","affiliation":[{"name":"Department of Geography, Ludwig-Maximilians-Universit\u00e4t M\u00fcnchen, Luisenstra\u00dfe 37, D-80333 Munich, Germany"}]}],"member":"1968","published-online":{"date-parts":[[2017,7,14]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"208","DOI":"10.1016\/j.rse.2011.10.035","article-title":"Spatially constrained inversion of radiative transfer models for improved LAI mapping from future Sentinel-2 imagery","volume":"120","author":"Atzberger","year":"2012","journal-title":"Remote Sens. Environ."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"102","DOI":"10.1016\/j.rse.2016.10.009","article-title":"Multitemporal and multiresolution leaf area index retrieval for operational local rice crop monitoring","volume":"187","author":"Nutini","year":"2016","journal-title":"Remote Sens. Environ."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"257","DOI":"10.1109\/TGRS.2013.2238242","article-title":"Optimizing lut-based rtm inversion for semiautomatic mapping of crop biophysical parameters from Sentinel-2 and-3 data: Role of cost functions","volume":"52","author":"Verrelst","year":"2014","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"260","DOI":"10.1016\/j.isprsjprs.2015.04.013","article-title":"Experimental Sentinel-2 LAI estimation using parametric, non-parametric and physical retrieval methods\u2014A comparison","volume":"108","author":"Verrelst","year":"2015","journal-title":"ISPRS J. Photogramm. Remote Sens."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"16062","DOI":"10.3390\/rs71215815","article-title":"Building a data set over 12 globally distributed sites to support the development of agriculture monitoring applications with Sentinel-2","volume":"7","author":"Bontemps","year":"2015","journal-title":"Remote Sens."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"10321","DOI":"10.3390\/rs70810321","article-title":"Retrieval of seasonal leaf area index from simulated enmap data through optimized lut-based inversion of the prosail model","volume":"7","author":"Locherer","year":"2015","journal-title":"Remote Sens."},{"key":"ref_7","unstructured":"Atzberger, C., Jarmer, T., Schlerf, M., K\u00f6tz, B., and Werner, W. (2003, January 13\u201316). Retrieval of wheat bio-physical attributes from hyperspectral data and sailh+ prospect radiative transfer model. Proceedings of the 3rd EARSeL Workshop on Imaging Spectroscopy, Herrsching, Germany."},{"key":"ref_8","first-page":"12","article-title":"Inversion of the prosail model to estimate leaf area index of maize, potato, and sunflower fields from unmanned aerial vehicle hyperspectral data","volume":"26","author":"Duan","year":"2014","journal-title":"Int. J. Appl. Earth Obs. Geoinf."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"415","DOI":"10.1016\/j.rse.2010.09.012","article-title":"Optimal modalities for radiative transfer-neural network estimation of canopy biophysical characteristics: Evaluation over an agricultural area with chris\/proba observations","volume":"115","author":"Verger","year":"2011","journal-title":"Remote Sens. Environ."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"353","DOI":"10.5194\/isprsannals-I-7-353-2012","article-title":"Hyperspectral reflectance signatures and point clouds for precision agriculture by light weight uav imaging system","volume":"I-7","author":"Honkavaara","year":"2012","journal-title":"ISPRS Ann. Photogramm. Remote Sens. Spat. Inf. Sci."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"725","DOI":"10.3390\/rs70100725","article-title":"Angular dependency of hyperspectral measurements over wheat characterized by a novel uav based goniometer","volume":"7","author":"Burkart","year":"2015","journal-title":"Remote Sens."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"230","DOI":"10.5589\/m09-010","article-title":"Experimental assessment of the Sentinel-2 band setting for rtm-based LAI retrieval of sugar beet and maize","volume":"35","author":"Richter","year":"2009","journal-title":"Can. J. Remote Sens."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"3140","DOI":"10.1109\/JSTARS.2015.2406339","article-title":"Generation of spectral-temporal response surfaces by combining multispectral satellite and hyperspectral uav imagery for precision agriculture applications","volume":"8","author":"Gevaert","year":"2015","journal-title":"IEEE J. Sel. Top. Appl. Earth Obs. Remote Sens."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"582","DOI":"10.1109\/JPROC.2012.2196249","article-title":"Using high-resolution airborne and satellite imagery to assess crop growth and yield variability for precision agriculture","volume":"101","author":"Yang","year":"2013","journal-title":"Proc. IEEE"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1007\/BF01058007","article-title":"A review and integrating analysis of spatially-variable control of crop production","volume":"33","author":"Schueller","year":"1992","journal-title":"Fertil. Res."},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Baret, F., and Buis, S. (2008). Estimating canopy characteristics from remote sensing observations. Review of methods and associated problems. Adv. Land Remote Sens. Syst. Model. Invers. Appl., 173\u2013201.","DOI":"10.1007\/978-1-4020-6450-0_7"},{"key":"ref_17","unstructured":"Danner, M., Hank, T., and Mauser, W. (2016, January 9\u201313). Comparing the potential of the Sentinel-2 msi and the future enmap hsi for the retrieval of winter wheat crop parameters in southern germany. Proceedings of the Living Planet Symposium, Prague, Czech Republic."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"125","DOI":"10.1016\/0034-4257(84)90057-9","article-title":"Light scattering by leaf layers with application to canopy reflectance modeling: The sail model","volume":"16","author":"Verhoef","year":"1984","journal-title":"Remote Sens. Environ."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1080\/02757258809532105","article-title":"Models of vegetation canopy reflectance and their use in estimation of biophysical parameters from reflectance data","volume":"4","author":"Goel","year":"1988","journal-title":"Remote Sens. Rev."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"75","DOI":"10.1016\/0034-4257(90)90100-Z","article-title":"Prospect: A model of leaf optical properties spectra","volume":"34","author":"Jacquemoud","year":"1990","journal-title":"Remote Sens. Environ."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"S56","DOI":"10.1016\/j.rse.2008.01.026","article-title":"Prospect+ sail models: A review of use for vegetation characterization","volume":"113","author":"Jacquemoud","year":"2009","journal-title":"Remote Sens. Environ."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"381","DOI":"10.1080\/02757250009532396","article-title":"Inversion methods for physically-based models","volume":"18","author":"Kimes","year":"2000","journal-title":"Remote Sens. Rev."},{"key":"ref_23","unstructured":"Jacquemoud, S., Flasse, S., Verdebout, J., and Schmuck, G. (1994, January 17\u201321). Comparison of several optimization methods to extract canopy biophysical parameters-application to caesar data. Proceedings of the 6th International Symposium on Physical Measurements and Signatures in Remote Sensing, Val D\u2019Isere, France."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/S0034-4257(02)00035-4","article-title":"Retrieval of canopy biophysical variables from bidirectional reflectance: Using prior information to solve the ill-posed inverse problem","volume":"84","author":"Combal","year":"2003","journal-title":"Remote Sens. Environ."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"501","DOI":"10.1177\/0309133307084626","article-title":"Recent developments in estimating land surface biogeophysical variables from optical remote sensing","volume":"31","author":"Liang","year":"2007","journal-title":"Prog. Phys. Geogr."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"2592","DOI":"10.1016\/j.rse.2007.12.003","article-title":"Inversion of a radiative transfer model for estimating vegetation LAI and chlorophyll in a heterogeneous grassland","volume":"112","author":"Darvishzadeh","year":"2008","journal-title":"Remote Sens. Environ."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"3","DOI":"10.1051\/agro:2000105","article-title":"Investigation of a model inversion technique to estimate canopy biophysical variables from spectral and directional reflectance data","volume":"20","author":"Weiss","year":"2000","journal-title":"Agronomie"},{"key":"ref_28","unstructured":"Baret, F., Knyazikhin, Y., Weiss, M., Pragn\u00e8re, A., and Myneni, R. (1999, January 18\u201322). Overview of retrieval techniques for LAI and fapar. Proceedings of the ALPS99 Workshop, Meribel, France."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"8830","DOI":"10.3390\/rs70708830","article-title":"The enmap spaceborne imaging spectroscopy mission for earth observation","volume":"7","author":"Guanter","year":"2015","journal-title":"Remote Sens."},{"key":"ref_30","unstructured":"Guanter, L., Kaufmann, H., Foerster, S., Brosinsky, A., Wulf, H., Bochow, M., Boesche, N., Brell, M., Buddenbaum, H., and Chabrillat, S. (2016). Enmap Science Plan, GFZ."},{"key":"ref_31","unstructured":"Loizzo, R., Ananasso, C., Guarini, R., Lopinto, E., Candela, L., and Pisani, A. (2016, January 9\u201313). The prisma hyperspectral mission. Proceedings of the Living Planet Symposium, Prague, Czech Republic."},{"key":"ref_32","doi-asserted-by":"crossref","unstructured":"Storch, T., Bachmann, M., Eberle, S., Habermeyer, M., Makasy, C., de Miguel, A., M\u00fchle, H., and M\u00fcller, R. (2013). Enmap ground segment design: An overview and its hyperspectral image processing chain. Earth Observation of Global Changes, Springer.","DOI":"10.1007\/978-3-642-32714-8_4"},{"key":"ref_33","unstructured":"Stuffler, T., Hofer, S., Leipold, M., F\u00f6rster, K., Sang, B., Schubert, J., Penn\u00e9, B., Kaufmann, H., M\u00fcller, A., and Chlebek, C. (2009, January 16\u201319). Enmap\u2014Space segment\u2014Instrument and mission parameters. Proceedings of the EARSeL SIG-IS Workshop, Tel Aviv, Israel."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"1627","DOI":"10.1021\/ac60214a047","article-title":"Smoothing and differentiation of data by simplified least squares procedures","volume":"36","author":"Savitzky","year":"1964","journal-title":"Anal. Chem."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"264","DOI":"10.1016\/0019-1035(86)90108-9","article-title":"Bidirectional reflectance spectroscopy: 4. The extinction coefficient and the opposition effect","volume":"67","author":"Hapke","year":"1986","journal-title":"Icarus"},{"key":"ref_36","unstructured":"Kaufmann, H., Hill, J., Hostert, P., Krasemann, H., Mauser, W., and Muller, A. (2012). Science Plan of the Environmental Mapping and Analysis Program (ENMAP), Deutsches GeoForschungsZentrum GFZ."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"522","DOI":"10.1109\/JSTARS.2012.2188994","article-title":"Eetes\u2014The enmap end-to-end simulation tool","volume":"5","author":"Segl","year":"2012","journal-title":"IEEE J. Sel. Top. Appl. Earth Obs. Remote Sens."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"141","DOI":"10.1016\/0034-4257(95)00136-O","article-title":"The robustness of canopy gap fraction estimates from red and near-infrared reflectances: A comparison of approaches","volume":"54","author":"Baret","year":"1995","journal-title":"Remote Sens. Environ."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"222","DOI":"10.1016\/S0034-4257(98)00060-1","article-title":"Physical mechanisms in hyperspectral brdf data of grass and watercress","volume":"66","author":"Sandmeier","year":"1998","journal-title":"Remote Sens. Environ."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"1730","DOI":"10.1109\/JSTARS.2013.2261474","article-title":"LAI retrieval using prosail model and optimal angle combination of multi-angular data in wheat","volume":"6","author":"Wang","year":"2013","journal-title":"IEEE J. Sel. Top. Appl. Earth Obs. Remote Sens."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"865","DOI":"10.1007\/s00442-010-1901-0","article-title":"Tracking plant physiological properties from multi-angular tower-based remote sensing","volume":"165","author":"Hilker","year":"2011","journal-title":"Oecologia"},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"19","DOI":"10.1007\/s12524-011-0129-8","article-title":"Inversion of prosail model for retrieval of plant biophysical parameters","volume":"40","author":"Tripathi","year":"2012","journal-title":"J. Indian Soc. Remote Sens."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"166","DOI":"10.1016\/j.rse.2006.12.013","article-title":"Coupled soil-leaf-canopy and atmosphere radiative transfer modeling to simulate hyperspectral multi-angular surface reflectance and toa radiance data","volume":"109","author":"Verhoef","year":"2007","journal-title":"Remote Sens. Environ."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"5063","DOI":"10.1080\/01431160802036490","article-title":"Retrieval of leaf area index from chris\/proba data: An analysis of the directional and spectral information content","volume":"29","author":"Vuolo","year":"2008","journal-title":"Int. J. Remote Sens."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"51","DOI":"10.1016\/S0098-8472(02)00010-2","article-title":"Changes in morphological and physiological traits during leaf expansion of arbutus unedo","volume":"48","author":"Gratani","year":"2002","journal-title":"Environ. Exp. Bot."},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"800","DOI":"10.2134\/agronj1984.00021962007600050021x","article-title":"Simple beta distribution representation of leaf orientation in vegetation canopies","volume":"76","author":"Goel","year":"1984","journal-title":"Agron. J."},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"350","DOI":"10.1016\/0076-6879(87)48036-1","article-title":"[34] chlorophylls and carotenoids: Pigments of photosynthetic biomembranes","volume":"148","author":"Lichtenthaler","year":"1987","journal-title":"Methods Enzymol."},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"23","DOI":"10.1016\/S0034-4257(03)00143-3","article-title":"Simulation of hyperspectral and directional radiance images using coupled biophysical and atmospheric radiative transfer models","volume":"87","author":"Verhoef","year":"2003","journal-title":"Remote Sens. Environ."},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"1222","DOI":"10.1109\/JSTARS.2012.2186118","article-title":"Inversion of a radiative transfer model for estimation of rice canopy chlorophyll content using a lookup-table approach","volume":"5","author":"Darvishzadeh","year":"2012","journal-title":"IEEE J. Sel. Top. Appl. Earth Obs. Remote Sens."},{"key":"ref_50","unstructured":"Wainwright, J., and Mulligan, M. (2005). Environmental Modelling: Finding Simplicity in Complexity, John Wiley & Sons."},{"key":"ref_51","doi-asserted-by":"crossref","unstructured":"Richter, K., Atzberger, C., Hank, T.B., and Mauser, W. (2012). Derivation of biophysical variables from earth observation data: Validation and statistical measures. J. Appl. Remote Sens., 6.","DOI":"10.1117\/1.JRS.6.063557"},{"key":"ref_52","doi-asserted-by":"crossref","first-page":"18","DOI":"10.1109\/JSTARS.2011.2171181","article-title":"Improving the robustness of cotton status characterisation by radiative transfer model inversion of multi-angular chris\/proba data","volume":"5","author":"Dorigo","year":"2012","journal-title":"IEEE J. Sel. Top. Appl. Earth Obs. Remote Sens."},{"key":"ref_53","doi-asserted-by":"crossref","first-page":"243","DOI":"10.1016\/S0034-4257(97)00138-7","article-title":"Variability in leaf and litter optical properties: Implications for brdf model inversions using avhrr, modis, and misr","volume":"63","author":"Asner","year":"1998","journal-title":"Remote Sens. Environ."},{"key":"ref_54","first-page":"107","article-title":"Inversion of radiative transfer model for retrieval of wheat biophysical parameters from broadband reflectance measurements","volume":"3","author":"Sehgal","year":"2016","journal-title":"Inf. Process. Agric."},{"key":"ref_55","first-page":"1","article-title":"Artmo\u2019s global sensitivity analysis (gsa) toolbox to quantify driving variables of leaf and canopy radiative transfer models","volume":"14","author":"Verrelst","year":"2015","journal-title":"EARSeL eProc."},{"key":"ref_56","doi-asserted-by":"crossref","first-page":"281","DOI":"10.1016\/0034-4257(93)90022-P","article-title":"Inversion of the prospect+ sail canopy reflectance model from aviris equivalent spectra: Theoretical study","volume":"44","author":"Jacquemoud","year":"1993","journal-title":"Remote Sens. Environ."},{"key":"ref_57","doi-asserted-by":"crossref","first-page":"204","DOI":"10.1016\/j.rse.2017.03.004","article-title":"Prospect-d: Towards modeling leaf optical properties through a complete lifecycle","volume":"193","author":"Gitelson","year":"2017","journal-title":"Remote Sens. Environ."},{"key":"ref_58","doi-asserted-by":"crossref","first-page":"8","DOI":"10.1109\/JSTARS.2012.2184268","article-title":"Vegetation structure retrieval in beech and spruce forests using spectrodirectional satellite data","volume":"5","author":"Schlerf","year":"2012","journal-title":"IEEE J. Sel. Top. Appl. Earth Obs. Remote Sens."}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/9\/7\/726\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T18:42:40Z","timestamp":1760208160000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/9\/7\/726"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2017,7,14]]},"references-count":58,"journal-issue":{"issue":"7","published-online":{"date-parts":[[2017,7]]}},"alternative-id":["rs9070726"],"URL":"https:\/\/doi.org\/10.3390\/rs9070726","relation":{},"ISSN":["2072-4292"],"issn-type":[{"value":"2072-4292","type":"electronic"}],"subject":[],"published":{"date-parts":[[2017,7,14]]}}}