Inspried by Shigeru Kobayashi‘s work and the desire to just make something, I created a google map visualisation of radiation readings from across Japan.
These are crowd-source readings from numerous geiger counters hooked up to the Internet. The folks at Pachube have aggregated these readings and made them available for people to play with. The readings come from sources such as local councils, motivated individuals and official readings from Japan’s Ministry of Education, Culture, Sports, Science and Technology (MEXT).
My aim with this map is to make the data easily readable and understandable, so people can very quickly get an overview of the radiation levels across Japan and are able to drill in to get further details per region.
From a user experience point-of-view, I wanted the numbers to be at a glance, avoiding the extra clicks that these mashups usually ask of the user. So you see the readings highlighted in yellow on the map. The orange circles are coloured based on the severity of the reading (the darker the orange, the higher the reading). Clicking on these circles will also bring up more details about the reading (location, timestamp, millisievert).
The toughest part of this visualisation is really understanding what the numbers mean and what impact they have on human health. The first step to this process is standardising the units of measurement, as the crowd-sourced measurements and visualisations may use a number of representations. Units here are in µSv/h (or microSieverts) and we’ve been hearing CNN and NHK World refer to the unit Milisieverts (1 miliSievert = 1000 microSieverts). I also urge other mappers out there to use the µSv/h unit, so we speak a common language.
Next we have to know what normal readings might be and what doses would result in impact on human health.
I’ve seen a few different references to ‘average background radiation’ on the web. But it’s been hard to decide which ones to use and what factors were included in these considerations of background radiation.
On the map, I’ve opted to refer to the average geiger counter reading across Japan, calculated from values provided by MEXT – 714.929 µSv / year. (http://notice.yahoo.co.jp/emg/en/archives/np_jp.html). When you click on a reading to get further details, you’ll see each reading compared to the national average. I’ve also included the US natural background radiation value from Wikipedia (3000 microSieverts / year), however, the calculation of this value is unknown and may include more types of exposure than just open air geiger counter readings.
Time is also a factor as exposure is cumulative and we normally measure how much radiation we gather in our bodies based on annual exposure, rather than hourly.
Here’s a quick table to better understand the impact of millisievert exposure (gathered via Wikipedia):
- 3 milsiv. average annual background (US)
- 10 milsiv aircrew annual exposure
- 50 milsiv current legal annual max
- 100 milsiv carcenogenic annual level
- 250 milsiv damage bone marrow, spleen
- 1000 milsiv 5% death
Monday, March 21, 2011
Here are 2 screenshots 12 minutes apart. The first one is March 20 @ 21:14 (GMT) and March 20 @ 21:26
Here are some great links to other resources: