{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,18]],"date-time":"2026-01-18T00:52:06Z","timestamp":1768697526754,"version":"3.49.0"},"reference-count":45,"publisher":"MDPI AG","issue":"10","license":[{"start":{"date-parts":[[2015,10,26]],"date-time":"2015-10-26T00:00:00Z","timestamp":1445817600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"JSPS KAKENHI","award":["26850164"],"award-info":[{"award-number":["26850164"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>A ground-based network of spectral observations is useful for ecosystem monitoring and validation of satellite data. However, these observations contain inherent uncertainties due to the change of sunlight conditions. This study investigated the impact of changing solar zenith angles and diffuse\/direct light conditions on the consistency of vegetation indices (normalized difference vegetation index (NDVI) and green-red vegetation index (GRVI)) derived from ground-based spectral measurements in three different types of cropland (paddy field, upland field, cultivated grassland) in Japan. In general, the vegetation indices decreased with decreasing solar zenith angle. This response was affected significantly by the growth stage and diffuse\/direct light conditions. The decreasing response of the NDVI to the decreasing solar zenith angle was high during the middle growth stage (0.4 &lt; NDVI &lt; 0.8). On the other hand, a similar response of the GRVI was evident except in the early growth stage (GRVI &lt; 0). The response of vegetation indices to the solar zenith angle was evident under clear sky conditions but almost negligible under cloudy sky conditions. At large solar zenith angles, neither the NDVI nor the GRVI were affected by diffuse\/direct light conditions in any growth stage. These experimental results were supported well by the results of simulations based on a physically-based canopy reflectance model (PROSAIL). Systematic selection of the data from continuous diurnal spectral measurements in consideration of the solar light conditions would be effective for accurate and consistent assessment of the canopy structure and functioning.<\/jats:p>","DOI":"10.3390\/rs71014079","type":"journal-article","created":{"date-parts":[[2015,10,26]],"date-time":"2015-10-26T12:48:03Z","timestamp":1445863683000},"page":"14079-14098","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":54,"title":["The Impact of Sunlight Conditions on the Consistency of Vegetation Indices in Croplands\u2014Effective Usage of Vegetation Indices from Continuous Ground-Based Spectral Measurements"],"prefix":"10.3390","volume":"7","author":[{"given":"Mitsunori","family":"Ishihara","sequence":"first","affiliation":[{"name":"National Institute for Agro-Environmental Sciences, 3-1-3 Kannondai, Tsukuba, Ibaraki 305-8604, Japan"}]},{"given":"Yoshio","family":"Inoue","sequence":"additional","affiliation":[{"name":"National Institute for Agro-Environmental Sciences, 3-1-3 Kannondai, Tsukuba, Ibaraki 305-8604, Japan"}]},{"given":"Keisuke","family":"Ono","sequence":"additional","affiliation":[{"name":"National Institute for Agro-Environmental Sciences, 3-1-3 Kannondai, Tsukuba, Ibaraki 305-8604, Japan"}]},{"given":"Mariko","family":"Shimizu","sequence":"additional","affiliation":[{"name":"Graduate School of Agriculture, Hokkaido University, Kita 9, Nishi 9, Kita-ku, Sapporo,  Hokkaido 060-8589, Japan"},{"name":"Civil Engineering Research Institute for Cold Region, National Research and Development Agency Public Works Research Institute, 3-1-43 Hiragishi Ichijo, Toyohira-ku, Sapporo,  Hokkaido 062-8602, Japan"}]},{"given":"Shoji","family":"Matsuura","sequence":"additional","affiliation":[{"name":"National Agriculture and Food Research Organization Institute of Livestock and Grassland Science, 768 Senbonmatsu, Nasushiobara, Tochigi 329-2793, Japan"}]}],"member":"1968","published-online":{"date-parts":[[2015,10,26]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"117","DOI":"10.2134\/agronj2006.0370c","article-title":"Application of spectral remote sensing for agronomic decisions","volume":"100","author":"Hatfield","year":"2008","journal-title":"Agron. J."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"210","DOI":"10.1016\/j.rse.2012.08.026","article-title":"Diagnostic mapping of canopy nitrogen content in rice based on hyperspectral measurements","volume":"126","author":"Inoue","year":"2012","journal-title":"Remote Sens. Environ."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"186","DOI":"10.1016\/j.rse.2012.10.005","article-title":"Remote estimation of gross primary productivity in crops using MODIS 250 m data","volume":"128","author":"Peng","year":"2013","journal-title":"Remote Sens. Environ."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/j.rse.2013.08.023","article-title":"Efficient corn and soybean mapping with temporal extendability: A multi-year experiment using Landsat imagery","volume":"140","author":"Zhong","year":"2014","journal-title":"Remote Sens. Environ."},{"key":"ref_5","first-page":"451","article-title":"Estimating rice grain protein contents with SPOT\/HRV data acquired at maturing stage","volume":"23","author":"Asaka","year":"2003","journal-title":"J. Remote Sens. Soc. Jpn."},{"key":"ref_6","first-page":"185","article-title":"Operational use of remote sensing for harvest management of rice","volume":"33","author":"Sakaiya","year":"2013","journal-title":"J. Remote Sens. Soc. Jpn."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"3467","DOI":"10.3390\/rs70403467","article-title":"Rice fields mapping in fragmented area using multi-temporal HJ-1A\/B CCD images","volume":"7","author":"Wang","year":"2015","journal-title":"Remote Sens."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"288","DOI":"10.1080\/2150704X.2012.725482","article-title":"Relationship between X-band backscattering coefficients from high-resolution satellite SAR and biophysical variables in paddy rice","volume":"4","author":"Inoue","year":"2013","journal-title":"Remote Sens. Lett."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"5995","DOI":"10.3390\/rs6075995","article-title":"Potential of X-band images from high-resolution satellite SAR sensors to assess growth and yield in paddy rice","volume":"6","author":"Inoue","year":"2014","journal-title":"Remote Sens."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"257","DOI":"10.1016\/j.rse.2013.09.001","article-title":"Capability of C-band backscattering coefficients from high-resolution satellite SAR sensors to assess biophysical variables in paddy rice","volume":"140","author":"Inoue","year":"2014","journal-title":"Remote Sens. Environ."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"290","DOI":"10.3390\/rs2010290","article-title":"Acquisition of NIR-green-blue digital photographs from unmanned aircraft for crop monitoring","volume":"2","author":"Hunt","year":"2010","journal-title":"Remote Sens."},{"key":"ref_12","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_13","doi-asserted-by":"crossref","first-page":"7954","DOI":"10.3390\/s110807954","article-title":"Ground-based optical measurements at European flux sites: A review of methods, instruments and current controversies","volume":"11","author":"Balzarolo","year":"2011","journal-title":"Sensors"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"227","DOI":"10.1016\/j.rse.2006.04.003","article-title":"Spectral Network (SpecNet): What is it and why do we need it?","volume":"103","author":"Gamon","year":"2006","journal-title":"Remote Sens. Environ."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"211","DOI":"10.1007\/s11284-014-1239-x","article-title":"Review: Development of an in situ observation network for terrestrial ecological remote sensing: the Phenological Eyes Network (PEN)","volume":"30","author":"Nasahara","year":"2015","journal-title":"Ecol. Res."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"234","DOI":"10.1016\/j.rse.2012.03.012","article-title":"Ground-based Network of NDVI measurements for tracking temporal dynamics of canopy structure and vegetation phenology in different biomes","volume":"123","author":"Soudani","year":"2012","journal-title":"Remote Sens. Environ."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"4343","DOI":"10.1080\/01431160802549369","article-title":"Evaluation of optical satellite remote sensing for rice paddy phenology in monsoon Asia using a continuous in situ dataset","volume":"30","author":"Motohka","year":"2009","journal-title":"Int. J. Remote Sens."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"113","DOI":"10.1016\/j.agrformet.2011.10.014","article-title":"An alternative method using digital cameras for continuous monitoring of crop status","volume":"154\u2013155","author":"Sakamoto","year":"2012","journal-title":"Agric. For. Meteorol."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"135","DOI":"10.1016\/S0034-4257(02)00091-3","article-title":"First operational BRDF, Albedo and Nadir reflectance products from MODIS","volume":"83","author":"Schaaf","year":"2002","journal-title":"Remote Sens. Environ."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"2369","DOI":"10.3390\/rs2102369","article-title":"Applicability of green-red vegetation index for remote sensing of vegetation phenology","volume":"2","author":"Motohka","year":"2010","journal-title":"Remote Sens."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"6202","DOI":"10.1080\/01431161.2012.682660","article-title":"In situ examination of the relationship between various vegetation indices and canopy phenology in an evergreen coniferous forest, Japan","volume":"33","author":"Nagai","year":"2012","journal-title":"Int. J. Remote Sens."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"270","DOI":"10.1016\/j.rse.2015.03.027","article-title":"Continuous and long-term measurements of reflectance and sun-induced chlorophyll fluorescence by using novel automated field spectroscopy systems","volume":"164","author":"Cogliati","year":"2015","journal-title":"Remote Sens. Environ."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"39","DOI":"10.1016\/j.agrformet.2014.12.001","article-title":"The impact of solar illumination angle when using active optical sensing of NDVI to infer fAPAR in a pasture canopy","volume":"202","author":"Rahman","year":"2015","journal-title":"Agric. For. Meteorol."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"127","DOI":"10.1016\/0034-4257(79)90013-0","article-title":"Red and photographic infrared linear combinations for monitoring vegetation","volume":"8","author":"Tucker","year":"1979","journal-title":"Remote Sens. Environ."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"418","DOI":"10.2134\/agronj2005.0418","article-title":"Large-area maize yield forecasting using leaf area index based yield model","volume":"97","author":"Kiniry","year":"2005","journal-title":"Agron. J."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"115","DOI":"10.1016\/j.rse.2008.08.015","article-title":"Phenologically-tuned MODIS NDVI-based production anomaly estimates for Zimbabwe","volume":"113","author":"Funk","year":"2009","journal-title":"Remote Sens. Environ."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"7910","DOI":"10.1080\/01431161.2014.978039","article-title":"Usability of noise-free daily satellite-observed green-red vegetation index values for monitoring ecosystem changes in Borneo","volume":"35","author":"Nagai","year":"2014","journal-title":"Int. J. Remote Sens."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"747","DOI":"10.1016\/S1002-0160(10)60065-3","article-title":"Diffusivity models and greenhouse gases fluxes from a forest, pasture, grassland and corn field in Northern Hokkaido, Japan","volume":"20","author":"Nkongolo","year":"2010","journal-title":"Pedosphere"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"2209","DOI":"10.1111\/gcb.12188","article-title":"Canopy-scale relationships between stomatal conductance and photosynthesis in irrigated rice","volume":"19","author":"Ono","year":"2013","journal-title":"Glob. Change Biol."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"76","DOI":"10.1111\/grs.12042","article-title":"Seasonal carbon dynamics and the effects of manure application on carbon budget of a managed grassland in a temperate, humid region in Japan","volume":"60","author":"Matsuura","year":"2014","journal-title":"Grassl. Sci."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"6277","DOI":"10.5194\/bg-11-6277-2014","article-title":"Retrieval of the photochemical reflectance index for assessing xanthophyll cycle activity: A comparison of near-surface optical sensors","volume":"11","author":"Harris","year":"2014","journal-title":"Biogeosciences"},{"key":"ref_32","unstructured":"Application Notes Sensors for NDVI Calculations. Available online: http:\/\/www.skyeinstruments.com\/wp-content\/uploads\/Application-Notes-for-NDVI.pdf."},{"key":"ref_33","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_34","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_35","doi-asserted-by":"crossref","first-page":"165","DOI":"10.1016\/0034-4257(85)90072-0","article-title":"Earth observation modeling based on layer scattering matrices","volume":"17","author":"Verhoef","year":"1985","journal-title":"Remote Sens. Environ."},{"key":"ref_36","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_37","doi-asserted-by":"crossref","first-page":"471","DOI":"10.1016\/S0034-4257(00)00139-5","article-title":"Comparison of four radiative transfer models to simulate plant canopies reflectance: direct and inverse mode","volume":"74","author":"Jacquemoud","year":"2000","journal-title":"Remote Sens. Environ."},{"key":"ref_38","first-page":"39","article-title":"Estimating chlorophyll content from hyperspectral vegetation indices: Modeling and validation","volume":"202","author":"Wu","year":"2008","journal-title":"Agric. For. Meteorol."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"84","DOI":"10.1016\/S0034-4257(01)00241-3","article-title":"Retrieval of vegetation clumping index using hot spot signatures measured by POLDER instrument","volume":"79","author":"Lacaze","year":"2002","journal-title":"Remote Sens. Environ."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"351","DOI":"10.1016\/0034-4257(94)00110-9","article-title":"Dependence of NDVI and SAVI on sun\/sensor geometry and its effect on fAPAR relationships in Alfalfa","volume":"51","author":"Epiphanio","year":"1995","journal-title":"Remote Sens. Environ."},{"key":"ref_41","doi-asserted-by":"crossref","unstructured":"Kokhanovsky, A.A. (2006). Light Scattering Reviews: Single and Multiple Light Scattering, Springer-Praxis.","DOI":"10.1007\/3-540-37672-0"},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"2561","DOI":"10.1080\/01431160500033724","article-title":"Evaluation of MODIS and NOAA AVHRR vegetation indices with in situ measurements in a semi-arid environment","volume":"26","author":"Fensholt","year":"2005","journal-title":"Int. J. Remote Sens."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"547","DOI":"10.1016\/j.rse.2014.06.007","article-title":"An automated field spectrometer system for studying VIS, NIR and SWIR anisotropy for semi-arid savanna","volume":"152","author":"Huber","year":"2014","journal-title":"Remote Sens. Environ."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"213","DOI":"10.1016\/S0034-4257(01)00299-1","article-title":"Impact of nitrogen and environmental conditions on corn as detected by hyperspectral reflectance","volume":"80","author":"Strachan","year":"2002","journal-title":"Remote Sens. Environ."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"156","DOI":"10.1016\/j.rse.2007.04.011","article-title":"Normalized difference spectral indices for estimating photosynthetic efficiency and capacity at a canopy scale derived from hyperspectral and CO2 flux measurements in rice","volume":"112","author":"Inoue","year":"2008","journal-title":"Remote Sens. Environ."}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/7\/10\/14079\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T20:50:53Z","timestamp":1760215853000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/7\/10\/14079"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2015,10,26]]},"references-count":45,"journal-issue":{"issue":"10","published-online":{"date-parts":[[2015,10]]}},"alternative-id":["rs71014079"],"URL":"https:\/\/doi.org\/10.3390\/rs71014079","relation":{},"ISSN":["2072-4292"],"issn-type":[{"value":"2072-4292","type":"electronic"}],"subject":[],"published":{"date-parts":[[2015,10,26]]}}}