For my project I need to get a raster containing green leaf index (GLI) values of a whole region.
My first idea was to merge all raster tiles and then extract the data. Upon attempting this though, the process takes a couple hours whereafter the process crashes due to insufficient memory (since I have to use very high resolution rasters). So merging all tiles into a greater mosaic and thereafter extracting the GLI values using a raster calculator is not an option.
I am able to simply load all data tiles into QGIS and perform the calculations across the 2000 individual raster tiles, but I do not know how to extract the data based on a shapefile/greater raster (<- for context, I am performing MaxEnt species distribution modelling on the data later so need to have the GLI values as an .asc format)
How can I extract the GLI data into a polygon/raster format without having to merge all individual tiles?