Does cloud cover affect NDVI?
Yes, it affects the values of NDVI, and it may not give the desired results sometimes. The clouds effect on NDVI is then eliminated by selecting for each pixel the greatest value on any day during the 14-day period (the highest NDVI value is assumed to represent the maximum vegetation “greenness” during the period).
Why is atmospheric correction difficult?
11.3. Atmospheric correction of satellite measurements over inland water is challenging due to many factors. Some of the major challenges include terrestrial atmospheric pollution, high turbidity, floating objects, and the adjacency effect of neighboring land pixels, which significantly raise the reflectance of water.
How to calculate the ndwi of Landsat 7?
Table 1. Landsat 7 and Landsat 8 data bands with their resolution and wavelength (NDWI) & Normalized Difference Build up Index (NDBI) respectively. Th e spectral reflectance curve helps to understand these indexes. of frequenc y) and the associated percent reflectance for any given material.
How can I do atmospheric correction of Landsat 8 Oli image?
If you use the Landsat8 Level 2, then images are already atmospherically correct using ground data by USGS. Also it was scaled for TOA (Top Of atmosphere). If you use Landsat 8 Level 2 product by USGS, the TOA provided (TOA planetary reflectance, see with the band name mentioned “sr” surface reflectance).
How to calculate vegetation index from Landsat 8 image?
Features like Clouds, water and snow show better reflection in the visible range then the near-infrared range, while the difference is almost zero for rock and bare soil. Output of the NDVI method creates a single-band dataset that only shows greenery.
How to calculate the NDVI value of vegetation?
Table below shows the red and infrared bands reflectance values of features and their NDVI values. Water has an NDVI value less than 0, bare soils between 0 and 0.1, and vegetation over 0.1. Increase in the positive NDVI value means greener the vegetation. RED=DN values from RED band NIR=DN values from Near Infrared band COVER TYPE RED NIR