I am wanting to calculate the average trend in maximum annual NDVI in Iceland from 2010-2020 using MODIS MYD13Q1 V6. How would I do this?
I have currently inserted the NDVI bands from the MODIS (which I downloaded from the earth explorer website) in ArcMap for each year and used the cell statistics tool to calculate the maximum NDVI and used the raster calculator to remove any negative values, leaving me with maximum NDVI layers for 2010 through to 2020 but I do not know how to calculate the average trend for this period.
Please can someone advise me on how to do this and also any statistical analysis I could use - I am familiar with R so preferably using RStudio to do this statistical analysis, thanks!
You can use Mann-Kendall and Sen's slope estimator test for analyzing the trend in the datasets.
However, if you want to calculate the pixel by pixel level trend, you can do that with the help of python using Mann-Kendall and Sen's slope estimator test.
You can refer to my publication for the purpose
Article A Spatio-Temporal Assessment and Prediction of Surface Urban...
https://www.mdpi.com/1424-8220/19/17/3701
Hi for getting MODIS NDVI average trends take a look at the website below:
https://modis.ornl.gov/globalsubset/
You can choose a subset for any location on earth (including Icelnd) and receive average and standard deviations of MODIS NDVI for the selected area.
Also you can download ASCII file of the pixel values along with quality information and GeoTiff files.
There are several libraries incorporating fully developed routines in R that help you calculate trends. For instance, some of them you can find below (on the left is the package name and on the right the name of the routine):
EnvStats v2.3.1: -> kendallTrendTest, spatialEco: -> raster.kendall, trend v1.1.1: -> mk.test, wq v0.4.4: -> mannKen
You can use FAO cloud tools https://earthmap.org/?aoi=dz&boundary=level0&feature=union_result&layers=%7B%7D&map=%7B%22center%22%3A%7B%22lat%22%3A28.414852217500616%2C%22lng%22%3A1.6659165209065652%7D%2C%22zoom%22%3A5%2C%22type%22%3A%22roadmap%22%7D
Here you can calculate annual NDVI and extract
Goof Luck