Function Description
Vegetation plays an important role in the global ecosystem, and the use of Remote Sensing Imagery to obtain vegetation information has become an important direction in the study of climate and ecological change. NDVI data is closely related to many parameters of vegetation, and it is an important indicator to monitor the change of ground vegetation.
- NDVI (Normalized Difference Vegetation Index), namely normalized difference vegetation index, can separate vegetation from water and soil, can objectively reflect the change of vegetation coverage, and is the best indicator of vegetation growth status and vegetation coverage.
- NDVI is based on the reflectance of the Near Infrared Band and Red Band of the image. The expression is NDVI = (NIR-R)/ (NIR + R), where NIR is the reflectance of the Near Infrared Band and R is the reflectance of the Red Band.
- The NDVI result is bounded between -1, 1:
- Negative value indicates that the ground is covered with clouds, water, snow, etc., and is highly reflective to visible light;
- 0 indicates that there is rock or bare soil, etc., and NIR and R are approximately equal;
- Positive value indicates that there is vegetation coverage, and it increases with the increase of coverage;
Data description
Vegetation and water indices can be calculated by various satellite remote sensing data. At present, the calculation of NDVI/NDWI based on satellite Remote Sensing Imagery such as TM, SPOT/VEGETATION and MODIS is widely used in vegetation dynamic change monitoring, Land Use/Cover Detect Change, Crop and forage yield estimation and drought monitoring. Before using the function, users need to understand the remote sensing Data Type and distinguish the band meaning of remote sensing data. The following are examples of common satellite remote sensing data bands used to calculate NDVI/NDWI:
- For TM Satellite Image, there are 7 bands, where Band2 represents Green Band, Band3 represents Red Band, and Band4 represents Near Infrared Band. Then NDVI = (Band4 − Band3)/ (Band4 + Band3) and NDWI = (Band2 − Band4)/ (Band2 + Band4).
- For the SPOT-5 Satellite Image, where Band1 represents the near-infrared band, Band2 represents the red band, and Band3 represents the Green Band, then NDVI = (Band1-Band2)/ (Band1 + Band2). NDWI= (Band3-Band1)/(Band3+Band1)。
- For Landset 8 Satellite Image, OLI Land Imager data bands in Landset 8 include 9 bands, where Band3 represents Green Band and Band4 represents Red Band. Band5 stands for Near Infrared Band, then NDVI = (Band5-Band4)/ (Band5 + Band4) and NDWI = (Band3-Band5)/ (Band3 + Band5).
Function entrance
- Data tab, Data Processing, Grid, NDVI.
- Toolbox-> Data Processing-> Grid-> NDVI.
Parameter Description
- Red Band: Set the Red Band participating in the calculation. If the image is a single-band Dataset, select the Red Band Data set; if it is a multi-band Dataset, select the Red Band in the Dataset.
- Near Infrared Band: Set the Near Infrared Band participating in the calculation. If the image is a single-band Dataset, select the Near-Infrared Band Data set; Select the Near Infrared Band in the Dataset if it is a multiband Dataset.
- Result Data: Set the Datasource and Dataset where the Result Dataset is located, and the program will generate a grid Result Dataset according to the NDVI expression based on the set Red Band and Near Infrared Band
Application example
Landsat 8 Satellite Image data of a region in June 2013 and June 2018 are available, and the dynamic changes of vegetation cover in the region are compared by calculating the NDVI index of the same region in different years. The results are as follows: It can be seen from the figure that the vegetation coverage in 2013 is more luxuriant than that in 2018, and the vegetation coverage in 2018 has decreased.
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| Figure of NDVI results in 2013 | Figure of NDVI results in 2018 |
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