OSAVI - Optimized Soil-Adjusted Vegetation Index

OSAVI Optimized Soil-Adjusted Vegetation Index

The Optimized Soil-Adjusted Vegetation Index (OSAVI) is a vegetation index that has been used for various applications related to vegetation monitoring and assessment. OSAVI is derived from the original Soil-Adjusted Vegetation Index (SAVI) and is designed to reduce the influence of soil background reflectance on the vegetation index values. Here are some common applications of OSAVI:

• Vegetation Health Assessment: OSAVI is used to assess the health and vigor of vegetation. By quantifying the amount of photosynthetically active vegetation, it provides valuable information about plant growth, stress levels, and overall vegetation condition. OSAVI has been widely applied in agriculture, forestry, and ecological studies to monitor the health of crops, forests, and natural vegetation.

• Drought Monitoring: OSAVI is effective in monitoring drought conditions by measuring the amount of green biomass present in an area. By comparing OSAVI values over time, changes in vegetation density and health can be detected, helping to identify regions experiencing drought stress and water scarcity. This information is valuable for water resource management, agricultural planning, and early warning systems for drought-related disasters.

•  Land Degradation Assessment: OSAVI has been used to assess land degradation processes such as desertification, deforestation, and soil erosion. By comparing OSAVI values in degraded areas with those in undisturbed areas, it is possible to identify and quantify the extent of land degradation. This information aids in understanding the impact of human activities on vegetation cover and can guide land management practices for sustainable development.

• Crop Yield Estimation: OSAVI has been utilized in agriculture for estimating crop yields and assessing crop health. By analyzing the vegetation index values throughout the growing season, farmers and researchers can make informed decisions regarding irrigation, fertilization, and pest management. OSAVI aids in optimizing agricultural practices, improving crop productivity, and reducing the risk of crop failure.

Generic Formula (R is the reflectance at the wavelengths (nm) denoted by the subscripts):

Formula by Sentinel-2 bands: 

This index should only be analysed in the presence of the crop and only when there is an LAI of more than 0.3-0.5 otherwise the data, apart from being influenced by the effect of the soil, is unreliable. It should therefore only be used when there is almost complete vegetative soil cover.

The relationship between index value and chlorophyll content is not linear, so a range of variation within the range of 0.1 points has different meanings. For example if the range is 0.15-0.25, this variation has a major impact, while for the range 0.35-0.45 the gradient is minor.

The OSAVI index is inversely proportional to chlorophyll content: it therefore returns a value that is lower the higher the chlorophyll content.

References:

• Santra, A., Santra Mitra, S., Sinha, S. (2021). 'Estimation and counter- validation of LISS-III derived leaf area index in Deltaic vegetation', Caspian Journal of Environmental Sciences, 19(2), pp. 239-249. doi: 10.22124/cjes.2021.4741

• Rondeaux, G., Steven, M., & Baret, F. (1996). Optimization of soil-adjusted vegetation indices. Remote sensing of environment, 55(2), 95-107.