After the 3/11 Tohoku earthquake in 2011 it became obvious that there was no comprehensive data source of radiation levels so people were forced to guess if their communities were contaminated or not. Published data from official sources was so vague it was useless to most people, and to make things worse the global supply of geiger counters dried up almost instantly so people who wanted to find out if their neighborhoods, schools and houses were contaminated had no options available to them.
Safecast is a platform that was created by a group of people who decided to solve this problem themselves. By creating mobile radiation sensors huge areas could be scanned and documented. That data was then collected and published freely and openly for anyone to use in any way. Scientists, Universities and Data Visualization teams have been able to analyze the data and explore it and people have been able to see accurate radiation levels in their areas.
If this kind of data was available prior to 3/11 the world would have a much better idea of what actually happened at the Fukushima Daiichi plant. As it is we only have data from after the event so we must speculate. By collecting this data now we can create a baseline that future data can be compared against. Additionally, people can now make educated decisions about relocating their families based on actual data, not rumor.