How to Display NDVI from MODIS in Google Earth Engine

Normalized Difference Vegetation Index (NDVI) is a graphical indicator to analyze whether an area contains live green vegetation or not. NDVI is effective to discriminate vegetation area and non-vegetation area. Sometimes, NDVI is associated with vegetation density. But in order to create a representative density analysis, ground-truth check is necessary to calculate the accuracy of the vegetation density. The value of index ranges from -1 to 1. The vegetation commonly ranges between 0.2 to 0.8.

NDVI can be derived from different satellite images, such as MODIS and Landsat. The concept is the same, NDVI require the calculation of ‘Red Band’ and ‘Near Infrared (NIR) Band’.

The formula of NDVI is as such:

NDVI = (NIR — Red) / (NIR + Red)

When we want to calculate the NDVI, be careful on calling the band. The location of NIR and Red Bands are different within different satellite dataset. Taking an example, in Landsat 7, Red is located in band number 3 and NIR located in band number 4. In Landsat 8, Red is located in band number 4 and NIR located in band number 5. In MODIS, Red and NIR are represented by band 1 and 2. This is the underlying concept of calculating NDVI.

Currently Google Earth Engine already process the NDVI using Landsat and MODIS globally. Scientist and author may access it easily within the data catalog of GEE. So we do not need to calculate it one by one or calculate it manually. Using GEE is much more…