An Analysis of Angle-Based With Ratio-Based Vegetation Indices

• Published in: IEEE transactions on geoscience and remote sensing 2006-09, Vol.44 (9), p.2506-2513
• Main Authors: Zhangyan Jiang, Huete, A.R., Jing Li, Yunhao Chen
• Format: Article
• Language: English
• Subjects: angle-based vegetation indices; Animal, plant and microbial ecology; Applied geophysics; Approximation; Background noise; Biological and medical sciences; Contamination; Density; Dynamic range; Earth sciences; Earth, ocean, space; Exact sciences and technology; Extraterrestrial measurements; Fundamental and applied biological sciences. Psychology; General aspects. Techniques; Internal geophysics; MODIS; Monitoring; Monitors; Radiometry; Reflectivity; Remote sensing; Saturation; saturation effect; Soil (material); soil background effects; Soil measurements; Teledetection and vegetation maps; Vegetation; Vegetation mapping
• ISSN: 0196-2892; 1558-0644
• DOI: 10.1109/TGRS.2006.873205

Remotely sensed, angle-based vegetation indices that measure vegetation amounts by the angle between an approximated soil line and a simulated vegetation isoline in the red-near-infrared reflectance space were developed and evaluated in this paper. Unsalan and Boyer previously proposed an angle-based vegetation index, thetas (denoted as thetas NDVI in this paper), based on the normalized difference vegetation index (NDVI) with the objective of overcoming the saturation problem in the NDVI. However, thetas NDVI did not consider strong soil background influences present in the NDVI. To reduce soil background noise, an angle-based vegetation index, thetas SAVI , based on the soil-adjusted vegetation index (SAVI), was derived using trigonometric analysis. The performance of thetas NDVI and thetas SAVI was evaluated and compared with their corresponding vegetation indices, NDVI and SAVI. The soil background influence on thetas NDVI was found to be as significant as that on the NDVI. thetas NDVI was found to be more sensitive to vegetation amount than the NDVI at low vegetation density levels, but less sensitive to vegetation fraction at high vegetation density levels. Thus, the saturation effect at high vegetation density levels encountered in the NDVI was not mitigated by thetas NDVI . By contrast, thetas SAVI exhibited insignificant soil background effects and weaker saturation, as in SAVI, but also improved upon the dynamic range of SAVI. Analyses and evaluation suggest that thetas SAVI is an optimal vegetation index to assess and monitor vegetation cover across the entire range of vegetation fraction density levels and over a wide variety of soil backgrounds