Creates a data.frame mapping nightlight tile names to their vertice coordinates. This is used to
identify nightlight tiles as well as to build a spatial polygons dataframe used to plot the tiles. OLS
only has one tile for the whole world and thus has a dummy entry. OLS is included to
prevent code duplication by writing separate functions for OLS.
Usage
getNlTiles(nlType)
Arguments
nlType
the nlType of interest
Value
A data.frame of names of tiles and lon-lat coordinate of top-left corner of each