IIDj, is collecting available measurements since March 26 of 2011 to provide a consistent and comprehensive Japan Radiation Map. Most of the data used are updated hourly, however some sources provide data in larger intervals or require manual transcription; in this case we can not guarantee regular updates. We do intentionally refrain from using any interpretative elements - such as thresholds or advisories. This needs to happen somewhere else with more competent people involved. Measurements are interchangeably provided in Gray/Sievert units at the source. The Japan Radiation Map shows all measurements in the nano Sievert/hour (nSv/h) unit - following the simplified equation where 1 Gray (Gy) = 1 Sievert (Sv).