Soil Measurement Project

Japan uses data from radiation in the air to indicate evacuation levels, which is less reliable.

In Chernobyl, however, the level for evacuation was based on the more precise soil contamination measurements. The Japanese government does not measure the soil regularly. This is done by volunteers and organizations nationwide, like Fukushima 30-Year Project. The frequent measuring of soil in various places help certify the actual condition of real pollution.
You can learn the current food and soil measurements taken throughout Japan by citizen's hands in English by visiting:
Minna-no Date Site (Everyone's Data Site)

Minna-no Date Site (Everyone's Data Site)