gis

It is very common to see relief maps with shadow effects, also known as ‘hillshade’, which generates visual depth. How can we create these effects in R and how to include them in ggplot2?

Space-time information is vital in many disciplines, especially in climatology or meteorology, and this makes it necessary to have a format that allows a multidimensional structure. It is also important that this format has a high degree of interchange compatibility and can store a large number of data.

In April of this year, I made an animation of the 24-hour average temperature of January 2020, also showing the day-night cycle. My biggest problem was finding a way to project correctly the area at night without breaking the geometry. The easiest solution I found was rasterising the night polygon and then reprojecting it. Indeed, a vector approach could be used, but I have preferred to use raster data here.

A disadvantage of choropleth maps is that they tend to distort the relationship between the true underlying geography and the represented variable. It is because the administrative divisions do not usually coincide with the geographical reality where people live. Besides, large areas appear to have a weight that they do not really have because of sparsely populated regions. To better reflect reality, more realistic population distributions are used, such as land use. With Geographic Information Systems techniques, it is possible to redistribute the variable of interest as a function of a variable with a smaller spatial unit.