NDLI: A Sampling Strategy for Remotely Sensed LAI Product Validation Over Heterogeneous Land Surfaces

Content Provider	IEEE Xplore Digital Library
Author	Yelu Zeng Jing Li Qinhuo Liu Longhui Li Baodong Xu Gaofei Yin Jingjing Peng
Copyright Year	2008
Abstract	The development of efficient and systematic groundbased spatial sampling strategies is critical for the validation of medium-resolution satellite-derived leaf area index (LAI) products, particularly over heterogeneous land surfaces. In this paper, a new sampling strategy based on high-resolution vegetation index prior knowledge (SSVIP) is proposed to generate accurate LAI reference maps over heterogeneous areas. To capture the variability across a site, the SSVIP is designed to 1) stratify the nonhomogeneous area into zones with minimum within-class variance; 2) assign the number of samples to each zone using Neyman optimal allocation; and 3) determine the spatial distribution of samples with a nearest neighbor index. The efficiency of the proposed method was examined using different vegetation types and pixel heterogeneities. The results indicate that the SSVIP approach can properly divide a heterogeneous area into different vegetation cover zones. Whereas the LAI reference maps generated by SSVIP attain the target accuracy of 0.1 LAI units in cropland and broadleaf forest sites, the current sampling strategy based on vegetation type has a root mean square error (RMSE) of 0.14 for the same number of samples. SSVIP was compared with the current sampling strategy at 24 VALERI sites, and the results suggested that samples selected by SSVIP were more representative in the feature space and geographical space, which further indicated the reasonable validation over heterogeneous land surfaces.
Starting Page	3128
Ending Page	3142
Page Count	15
File Size	1935137
File Format	PDF
ISSN	19391404
Volume Number	7
Issue Number	7
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	2014-01-01
Publisher Place	U.S.A.
Access Restriction	Subscribed
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Vegetation mapping Accuracy Remote sensing Land surface Indexes Transfer functions Sociology sampling strategy Heterogeneous pixel leaf area index (LAI) prior knowledge product validation
Content Type	Text
Resource Type	Article
Subject	Atmospheric Science Computers in Earth Sciences

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