02159nas a2200229   4500008004100000245010200041210006900143300001500212490000700227520139300234100001601627700002301643700001701666700001601683700002001699700001801719700001901737700001801756700001401774700001601788856012501804       2006                        eng d00aMODIS land cover and LAI collection 4 product quality across nine sites in the western hemisphere0 aMODIS land cover and LAI collection 4 product quality across nin  a1843 -18570 v443 aGlobal maps of land cover and leaf area index (LAI) derived from the Moderate Resolution Imaging Spectrometer (MODIS) reflectance data are an important resource in studies of global change, but errors in these must be characterized and well understood. Product validation requires careful scaling from ground and related measurements to a grain commensurate with MODIS products. We present an updated BigFoot project protocol for developing 25-m validation data layers over 49-km2 study areas. Results from comparisons of MODIS and BigFoot land cover and LAI products at nine contrasting sites are reported. In terms of proportional coverage, MODIS and BigFoot land cover were in close agreement at six sites. The largest differences were at low tree cover evergreen needleleaf sites and at an Arctic tundra site where the MODIS product overestimated woody cover proportions. At low leaf biomass sites there was reasonable agreement between MODIS and BigFoot LAI products, but there was not a particular MODIS LAI algorithm pathway that consistently compared most favorably. At high leaf biomass sites, MODIS LAI was generally overpredicted by a significant amount. For evergreen needleleaf sites, LAI seasonality was exaggerated by MODIS. Our results suggest incremental improvement from Collection 3 to Collection 4 MODIS products, with some remaining problems that need to be addressed1 aCohen, W.B.1 aMaiersperger, T.K.1 aTurner, D.P.1 aRitts, W.D.1 aPflugmacher, D.1 aKennedy, R.E.1 aKirschbaum, A.1 aRunning, S.W.1 aCosta, M.1 aGower, S.T.  uhttp://129.130.186.12/content/modis-land-cover-and-lai-collection-4-product-quality-across-nine-sites-western-hemisphere02475nas a2200205   4500008004100000245010100041210006900142300001300211490000700224520178600231653001802017653000802035653001802043100001402061700001602075700001802091700002302109700001602132856012102148       2004                        eng d00aComparison of hyperspectral and multispectral data for estimating leaf area index in four biomes0 aComparison of hyperspectral and multispectral data for estimatin  a508 -5200 v913 aMotivated by the increasing importance of hyperspectral remote sensing data, this study sought to determine whether current-generation narrow-band hyperspectral remote sensing data could better track vegetation leaf area index (LAI) than traditional broad-band multispectral data. The study takes advantage of a unique dataset, wherein field measurements of LAI were acquired at the same general time and grain size as both Landsat ETM+ and AVIRIS (Airborne Visible/Infrared Imaging Spectrometer) imagery in four different biomes. Biome types sampled included row-crop agriculture, tallgrass prairie, mixed hardwood-conifer forest, and boreal conifer forest. The effects of bandwidth, band placement, and number of bands were isolated from radiometric quality by comparing regression models derived from individual AVIRIS channels with those derived from simulated ETM+ and MODIS channels using the AVIRIS data. Models with selected subsets of individual AVIRIS channels performed better to predict LAI than those based on the broadband datasets, although the potential to overfit models using the large number of available AVIRIS bands is a concern. Models based on actual ETM+ data were generally stronger than those based on simulated ETM+ data, suggesting that, for predicting LAI, ETM+ data suffer no penalty for having lower radiometric quality. NDVI was generally not sensitive to LAI at the four sites. Band placement of broad-band sensors (e.g., simulated ETM+ and MODIS) did not affect relationships with LAI, suggesting that there is no inherent advantage to MODIS spectral properties over those of ETM+ for estimating LAI. Spectral channels in the red-edge and shortwave-infrared regions were generally more important than those in the near-infrared for predicting LAI.10aHyperspectral10aLAI10aMultispectral1 aLee, K-S.1 aCohen, W.B.1 aKennedy, R.E.1 aMaiersperger, T.K.1 aGower, S.T.  uhttp://129.130.186.12/content/comparison-hyperspectral-and-multispectral-data-estimating-leaf-area-index-four-biomes03868nas a2200289   4500008004100000245017000041210006900211300001300280490000700293520292700300653001203227653000803239653000903247653001503256653002003271653001003291653001503301100001603316700002303332700001303355700001603368700001703384700001603401700002103417700001803438856012203456       2003                        eng d00aComparisons of land cover and LAI estimates derived from ETM+ and MODIS for four sites in North America: a quality assessment of 2000/2001 provisional MODIS products0 aComparisons of land cover and LAI estimates derived from ETM and  a221 -3620 v883 aThe MODIS land science team produces a number of standard products, including land cover and leaf area index (LAI). Critical to the success of MODIS and other sensor products is an independent evaluation of product quality. In that context, we describe a study using field data and Landsat ETM+ to map land cover and LAI at four 49-km2 sites in North America containing agricultural cropland (AGRO), prairie grassland (KONZ), boreal needleleaf forest, and temperate mixed forest. The purpose was to: (1) develop accurate maps of land cover, based on the MODIS IGBP (International Geosphere–Biosphere Programme) land cover classification scheme; (2) derive continuous surfaces of LAI that capture the mean and variability of the LAI field measurements; and (3) conduct initial MODIS validation exercises to assess the quality of early (i.e., provisional) MODIS products. ETM+ land cover maps varied in overall accuracy from 81% to 95%. The boreal forest was the most spatially complex, had the greatest number of classes, and the lowest accuracy. The intensive agricultural cropland had the simplest spatial structure, the least number of classes, and the highest overall accuracy. At each site, mapped LAI patterns generally followed patterns of land cover across the site. Predicted versus observed LAI indicated a high degree of correspondence between field-based measures and ETM+ predictions of LAI. Direct comparisons of ETM+ land cover maps with Collection 3 MODIS cover maps revealed several important distinctions and similarities. One obvious difference was associated with image/map resolution. ETM+ captured much of the spatial complexity of land cover at the sites. In contrast, the relatively coarse resolution of MODIS did not allow for that level of spatial detail. Over the extent of all sites, the greatest difference was an overprediction by MODIS of evergreen needleleaf forest cover at the boreal forest site, which consisted largely of open shrubland, woody savanna, and savanna. At the agricultural, temperate mixed forest, and prairie grassland sites, ETM+ and MODIS cover estimates were similar. Collection 3 MODIS-based LAI estimates were considerably higher (up to 4 m2 m−2) than those based on ETM+ LAI at each site. There are numerous probable reasons for this, the most important being the algorithms' sensitivity to MODIS reflectance calibration, its use of a prelaunch AVHRR-based land cover map, and its apparent reliance on mainly red and near-IR reflectance. Samples of Collection 4 LAI products were examined and found to consist of significantly improved LAI predictions for KONZ, and to some extent for AGRO, but not for the other two sites. In this study, we demonstrate that MODIS reflectance data are highly correlated with LAI across three study sites, with relationships increasing in strength from 500 to 1000 m spatial resolution, when shortwave-infrared bands are included.10aBigFoot10aETM10aIGBP10aLand cover10aLeaf area index10aMODIS10aValidation1 aCohen, W.B.1 aMaiersperger, T.K.1 aYang, Z.1 aGower, S.T.1 aTurner, D.P.1 aRitts, W.D.1 aBerterretche, M.1 aRunning, S.W.  uhttp://129.130.186.12/content/comparisons-land-cover-and-lai-estimates-derived-etm-and-modis-four-sites-north-america