Measuring shape irregularity in QGIS

QGIS is great for making basic maps, but it's also _really_ great for doing lots of more advanced spatial things. One such example is investigating shape irregularity using expressions, so in this video I take a look at how we can assess the irregularity of US state and county shapes, just as an example.

You can learn how to create a new column using the *Hausdorff distance* function, or just style a layer using this approach. _Who is Hausdorff? Felix Hausdorff was a German mathematician who also went by the pseudonym Paul Mongré - although I have no idea why!_

Which county has the most regularly shaped counties? Let's see!

Hausdorff distance: https://en.wikipedia.org/wiki/Hausdorff_distance

*Expressions I use in the video*

_hausdorff_distance($geometry,bounds($geometry))_ - this compares the shape of a polygon to its bounding box

_hausdorff_distance( $geometry, minimal_circle( $geometry,500))_ - this compares the shape of a polygon to its minimum bounding circle

_format_number(hausdorff_distance( $geometry,bounds($geometry)),4)_ - this adds a label to each polygon, formatted to have four decimal places, with the Hausdorff distance score for the polygon

US states shapefile: https://catalog.data.gov/dataset/tiger-line-shapefile-2019-nation-u-s-current-state-and-equivalent-national#:~:text=The%20TIGER%2FLine%20shapefiles%20and,TIGER)%20Database%20(MTDB).

US counties shapefile: https://catalog.data.gov/dataset/tiger-line-shapefile-2019-nation-u-s-current-county-and-equivalent-national-shapefile

See my intro and intermediate QGIS courses for more: https://www.udemy.com/user/alasdair-rae-2/

Thanks to Steven Kay for inspiration here.

Видео Measuring shape irregularity in QGIS канала Map Academy