Safecast Data FAQ
Some further details on Safecast data:
What is the source of Safecast’s data?
- Short answer: It was collected by SAFECAST volunteers using industry standard 2″ pancake sensors.
- Long answer: There are a number of different kinds of data represented on the SAFECAST website including crowd sourced measurements and aggregate data released by other agencies, however the official “SAFECAST data” that we reference and publish for others to use was collected by Safecast volunteers using professional quality devices. We use a combination of off the shelf commercial radiation monitors and devices we’ve built ourselves to better serve specific purposes. In both of these cases the devices use the same sensor, the LND7317 which is commonly referred to as the 2″ pancake. This is a highly sensitive piece of equipment that is used by nuclear professionals all over the world, and we have tested them and are confident and stand behind the readings taken with our devices. Additionally we frequently use several devices simultaneously to ensure against single device failure.
- One caveat: The world is a big place and it’s not reasonable to think we’ll be able to measure every inch of it with our small core team, and as we’ve grown we’ve been able to increasingly utilize crowdsourced measurements on every continent. As is often the case in these things, we’ve found that about 90% of our data has been collected by the most active 10% of our volunteers. We’re working very hard to make the variations in the equipment used transparent, and to ensure that all the data we publish is interoperable.
What are differences in the data published by SAFECAST and official/governmental sources?
- Short answer: SAFECAST data has higher resolution geographically and better consistency.
- Long answer: We know from our efforts that radiation levels can fluctuate in very short distances, so that simply crossing a street can sometimes yield dramatically different readings. Readings that have been published by official sources in most countries generally do not provide detailed geographic coverage, and sometimes reported data for an entire city is based on just a single reading. We feel this is at best too vague to be useful and at worse intentionally misleading. In the case of Japan since the Fukushima NPP accident, the government has made a lot of radiation data available, but SAFECAST’s data for the country provides demonstrably more detailed coverage for most areas, and is easily accessible online and through our iOS app. In particular, we have attempted to map radiation in Japan on a street by street level, with consistency in the devices we use. Finally all Safecast data is freely and openly published using a CC0 designation, in a form which makes it easy for others to generate their own visualizations and data comparisons. At present, many Japanese gov’t radiation datasets can be downloaded, but many come with restrictive use agreements, while others are not easily adaptable for independent use or research.
- One caveat: How measurements are taken is as important as what the measurement is. It is particularly important to know at what height readings have been taken. Official gov’t agencies and many research institutions often use readings taken by devices mounted on rooftops, 10 meters above the ground or more. SAFECAST volunteers are instructed to take standard environmental readings as close to 1m height as possible, and almost all of the data shown on our maps will be taken from that height. However, we are currently deploying a new fixed sensor network, and these devices may be mounted higher on buildings in some cases (the visualizations for the data from these devices is a work in progress, but will include this height data).
Is Safecast an anti-nuclear activist group?
- Short answer: No
- Long answer: Safecast is not anti-nuclear, nor pro-nuclear – we are pro-data. Data is apolitical. Safecast was created because we identified a lack of data and realized we could help fill that gap. Our goal is simply to provide more information, data where none previously existed, so that people can make more informed decisions based on facts rather than the fear and speculation that comes from uninformed rumor.
- One caveat: It’s worth noting that data can be interpreted in different ways, and visualized to highlight or downplay different aspects. This is why in addition to our visualizations we make our raw data available for anyone to examine and interpret on their own.
Is Safecast working with the Government?
- Short answer: No
- Long answer: SAFECAST is independent and has successfully remained uninfluenced by politics of any kind. Because of our jealously-guarded impartiality, SAFECAST has increasingly been viewed as an entity whose information and motivations are trusted on all sides. This has allowed us to function at times as an effective “go-between” for conflicted parties, such as environmental groups and government agencies, and to lobby effectively for increased openness in the process. SAFECAST does not accept government funding, but we welcome the input of sincere and open-minded experts wherever they are found.
- One caveat: SAFECAST strives to be completely transparent, and our data, device designs, and software designs are available for use by anyone, including government agencies. To the degree that this would imply that any agency doing this was becoming more like SAFECAST (as opposed to vice-versa), we’d be inclined to consider this a step in the right direction.
Are radiation readings affected by driving?
- Short answer: No
- Long answer: Under the radiation conditions we normally encounter, the speed of a moving car (with a geiger counter attached) does not affect the readings taken when compared against readings taken in the same area with a motionless sensor. Safecast has verified this through research collaborations with Keio, Tokyo, and Nihon Universities.
- One caveat: Safecast’s “bGeigie” system is mounted outside of the car so that readings are not affected by the car itself. Other groups, including the Japanese gov’t, have taken mobile readings from inside vehicles, which provides shielding and blocks out a portion of the radiation. It’s important to verify how readings are taken.