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Extraction of vegetation index requires processing of remote sensing images, which generally requires spectral reflectance or emissivity. Specific operation steps are as follows:
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Open ENVI software and load the remote sensing image.
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Select the region of interest(ROI) or feature and extract it as a spectral curve. From the ENVI menu, select the "ROI Tools" option, then select the "Draw Polygon" tool or other area of interest tool.
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Open the "Spectral Profile" tool. In the ENVI menu, select "Spectral Analysis" and then "Spectral Profile".
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In the "Spectral Profile" window, select the vegetation index to be calculated. Vegetation index is an index used to describe vegetation growth, such as NDVI(normalized Vegetation index), SAVI(land regulated Vegetation index), etc. After selecting the exponent, click the "Add" button to add the exponent to "Expression".
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In the "Spectral Profile" window, set the data type. Select "Reflectance" or "Radiance" based on the data type of input data.
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Click the "Compute" button, and ENVI will calculate the selected exponent and display the result in the graph window. You can make further edits to the graph and save the results to a file.
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It is very convenient to extract the vegetation index from ENVI because ENVI already contains many standard vegetation indexes and provides visualization and calculation tools. Note, however, that you must use the correct data types and parameter Settings to get accurate results. At the same time, other remote sensing software or programming language can also be used to extract vegetation index, the specific operation may be different from ENVI.
