the dot density map

One dot for a fixed number of things, dropped where they happen. Where the dots crowd together, so does the thing.

What it leaves outThe dots are scattered at random inside each area — they are not real addresses. A coarse dot-per-count can make a busy place look empty.

3 · geospatial · geo · level 3 · compare and choose · taught in dive 3.4

Two worked examples

Where do the earthquakes actually happen?

Before you lookDraw, from memory, where you think the line of quakes runs through California.

civicdots_la_311_points.csv · 1,500 rows · 4 columns · showing 400 of 1,500 rows on this page; the file has all of them

1,500 individual service requests, each with a latitude and longitude

What to look atWhere the requests concentrate — real reported locations, which is not true of every dot map. But concentration follows where the people are, so ask whether a dense patch is more problems or just more people.

This example draws itself with a small script. With scripting off you can still read every word on this page, and the file itself is at data/dots_la_311_points.csv.

earth and spacedots_quake_epicentres.csv · 2,508 rows · 6 columns · showing 400 of 2,508 rows on this page; the file has all of them

2,508 earthquake epicentres

What to look atThe dots trace the faults. Notice how the shape of the data is a shape in the ground.

This example draws itself with a small script. With scripting off you can still read every word on this page, and the file itself is at data/dots_quake_epicentres.csv.

the pool

Now build one yourself.

The pool opens with this file and this shape already drawn, so your first move is to change something rather than to start from nothing. Bring your own CSV if you have one. Nothing is uploaded anywhere — the chart is drawn in your browser, your work saves there, and it downloads as a picture or as a project file you can open again.

Open the pool → the dot density map · dots_la_311_points.csv