Day 24: only circular shapes

I already had the DEM data that I processed for Maria of the Moon. I figured I could reuse it to make something for today’s circular shape theme.

Steps:

In order to create the circular mesh, I needed to have a vector layer of the shape of the moon and then somehow get the data from the raster onto this layer. Here are the steps I took:

Create a new vector layer and draw the shape of the moon. qGIS has a nice circular shape setting when creating new features.
Create a grid from the new vector layer. I chose to create a hexagon grid. I played with the settings and ended up using 170 km for both vertical and horizontal spacing.
Zonal statistics: with this tool, select the hexagon grid as the vector input layer and DEM as the raster layer. This basically will get statistics from the raster for each hexagon in the grid. I only needed the mean elevation for each hexagon so thats the only selection I kept.
Now that the hexagon grid has mean elevation information, we need to create centroids for each hexagon to be able to make a map of dots/circles with the elevation. First, delete any hexagons that lie outside the circle representing the shape of the moon. Then, use the centroids tool to create centroids for each hexagon.
Repeat the steps above for the other side of the moon.
Finally, we can style the centroids using graduated symbols with the mean elevation values. For styling, I used natural breaks and edited the ranges to make sure I have the same ranges for both the near side and far side of the moon.

Tools used: qGIS, Illustrator