Animating noon shadows in Edinburgh using QGIS and SAGA

This looping animated GIF shows how the shadows fall at noon in Edinburgh over the course of a year (at 4 Mb it may stutter at first on a slow connection, but should play smoothly when it's loaded fully)

shadows at noon in central Edinburgh over the course of a year

shadows at noon in central Edinburgh over the course of a year

The very detailed DEM here is from GeoGeo (my employer), reproduced here with kind permission. The DEM is scaled down - the original is 3 to 4 cm/pixel; this was shrunk to around 0.6 m / pixel to make it manageable to process (try processing a 40k x 20k pixel raster on a laptop!) Even sampled down, it's possible to see the shadows of chimneys and parked cars.

How it was done

Used the 'potential incoming solar radiation' filter in SAGA GIS to calculate the amount of sunlight at exactly 12 Noon. There are 24 frames, looped as an animated GIF. Frames were snapshots of the 1st and 15th of each successive month. This means the days aren't equally spaced throughout the year, but within a couple of days of being equally spaced.

You might notice that the shadows trace out a figure-of-eight. For more info, see the wikipedia entry on the Analemma (tl;dr - the sun is not directly south at noon throughout the year)

These were loaded into QGIS, and a consistent gradient applied to each image (the scale is from black (0 Kw/h) to white (1000 Kw/h). This is a potential figure, assuming clear skies (not something that Edinburgh is famous for!). Being able to copy and paste styles across layers makes this very easy.

After exporting as images from QGIS, the frames were stiched into a gif using the ImageMagick convert command.