Geoscience Reference
In-Depth Information
4
CHAPTER
In Situ
Estimates of Forest LAI for
MODIS Data Validation
John S. Iiames, Jr., Andrew N. Pilant, and Timothy E. Lewis
CONTENTS
4.1 Introduction.............................................................................................................................41
4.1.1 Study Area .................................................................................................................43
4.2 Background.............................................................................................................................43
4.2.1 TRAC Measurements .................................................................................................43
4.2.2 Hemispherical Photography Measurements...............................................................45
4.2.3 Combining TRAC and Hemispherical Photography .................................................45
4.2.4 Satellite Data ..............................................................................................................46
4.2.5 MODIS LAI and NDVI Products ..............................................................................46
4.3 Methods ..................................................................................................................................47
4.3.1 Sampling Frame Design .............................................................................................47
4.3.2 Biometric Mensuration ...............................................................................................48
4.3.3 TRAC Measurements .................................................................................................50
4.3.4 Hemispherical Photography .......................................................................................51
4.3.5 Hemispherical Photography Quality Assurance ........................................................52
4.4 Discussion...............................................................................................................................52
4.4.1 LAI Accuracy Assessment .........................................................................................52
4.4.2 Hemispherical Photography .......................................................................................52
4.4.3 Satellite Remote Sensing Issues.................................................................................54
4.5 Summary.................................................................................................................................54
Acknowledgments ............................................................................................................................55
References ........................................................................................................................................55
4.1 INTRODUCTION
Satellite remote sensor data are commonly used to assess ecosystem conditions through synoptic
monitoring of terrestrial vegetation extent, biomass, and seasonal dynamics. Two commonly used
vegetation indices that can be derived from various remote sensor systems include the Normalized
Difference Vegetation Index (NDVI) and Leaf Area Index (LAI). Detailed knowledge of vegetation
41
