Invertible Canopy Reflectance Modeling of Vegetation Structure in Semiarid Woodland

Janet Franklin, Alan H. Strahler

Research output: Contribution to journalArticle

72 Scopus citations

Abstract

The Li-Strahler canopy reflectance model, driven by Landsat Thematic Mapper (TM) data, provided regional estimates of tree size and density in two bioclimatic zones in West Africa. This model exploits tree geometry in an inversion technique to predict average tree size and density from reflectance data using a few simple parameters measured in the field (spatial pattern, shape, and size distribution of trees) and in the imagery (spectral signatures of scene components). Trees are treated as simply shaped objects, and multispectral reflectance of a pixel is assumed to be related only to the proportions of tree crown, shadow, and understory in the pixel. These, in turn, are a direct function of the number and size of trees, the solar illumination angle, and the spectral signatures of crown, shadow, and understory. Given the variance in reflectance from pixel to pixel within a homogeneous area of woodland, caused by the variation in the number and size of trees, the model can be inverted to give estimates of average tree size and density. Because the inversion is sensitive to correct determination of component signatures, which is a difficult procedure at best, predictions of size and spacing are not very accurate within small (i.e., 10-100 ha) areas. However, individual errors cancel when larger regions are considered, and the procedure may predict size and density of trees over large areas of open woodland with good accuracy.

Original languageEnglish (US)
Pages (from-to)809-825
Number of pages17
JournalIEEE Transactions on Geoscience and Remote Sensing
Volume26
Issue number6
DOIs
StatePublished - Nov 1988

Keywords

  • Biophysical remote sensing
  • Landsat Thematic Mapper
  • West Africa
  • discrete object modeling
  • savanna

ASJC Scopus subject areas

  • Electrical and Electronic Engineering
  • Earth and Planetary Sciences(all)

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