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Download Maps

Below are some maps downloadable in Google Earth KMZ or PNG format.

My space to host this data is almost non-existent, so I am not able to make available all the source GIS data in Geiger Bot here.
  1. Download Safecast Background Subtracted Data (December 2012, Google Earth, 1.6 MB) (Japan only)
    1. (Alt: PNG format)
  2. Download AIST "Natural" Background Dose Rate Interpolation (AIST data from 2007, Google Earth, Japan only)
    1. (Alt: PNG format)
For more information on creation of the above maps, please see the bottom of the page for the original front page posts.

Data Sources:
  1. Safecast - Safecast data
  2. USGS / GSC - North America (NURE+) radiometric data
    1. Note: if exporting the Geosoft rasters use the following .prj file: PROJCS["DNAG",GEOGCS["GCS_STM1987",DATUM["D_STM1987",SPHEROID["STM1987",6371204.0,0.0]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Transverse_Mercator"],PARAMETER["False_Easting",0.0],PARAMETER["False_Northing",0.0],PARAMETER["Central_Meridian",-100.0],PARAMETER["Scale_Factor",0.926],PARAMETER["Latitude_Of_Origin",0.0],UNIT["Meter",1.0]]
    2. Note: Much more Canada data is available via the "Seeker" interface in Geosoft Oasis montaj (web download interface very limited)
  3. US DOE / NNSA - Japan aerial / ground vehicle surveys, 2011
  4. Geoscience Australia - Australia natural background rasters (not really available online)
  5. AIST - Japan mineral sample data
    1. See USGS report above for data processing methodology
  6. US NGA - DEMs used in cosmic dose rate calculation
    1. See USGS report above for data processing methodology
    2. (note: would suggest higher resolution source like SRTM)
  7. US NOAA - "Earth at Night" global radiance raster
  8. US EPA - Uranium mines database (TENORM)

Data Processing:
  1. ArcGIS for Desktop - Interpolations (Geostatistical Analyst - Empricial Bayesian Kriging, Spatial Analyst - Natural Neighbor), reprojections, format conversion etc
  2. Geosoft Oasis montaj viewer - Export of Geosoft raster data
  3. FME Desktop - Miscellaneous data conversion

Directly Reuse / Copy Internal Geiger Bot Map Data: [developers]
  • You can also extract the map tile databases from Geiger Bot directly.
    • This is more involved technically, and this won't mean much to you if you're not a developer.
  • OS X: Download app from App Store in iTunes.  Right-click on the Geiger Bot .IPA installer package file.  Click open.  Copy and paste all .sqlite files to a real directory.
  • Legal: As far as I am concerned, you are free to do anything without limitations beyond that which were attached to the source datasets.
  • Caveat: In most cases working with the source data will be easier.
  • Data Overview:
    • Tile System / Projection:
      • Standard Web Mercator tiles
    • Container:
      • SQLite3 database, single table
    • File format:
      • RAW (zlib compressed)
  • Details:
    • Database Schema:
      • One database per layer / dataset.
      • One table per database.
      • sqlite> .schema Tiles
      • CREATE TABLE Tiles(ID INTEGER PRIMARY KEY, TileX INT, TileY INT, TileLevel INT, DataCount INT, TileData BLOB);
      • CREATE INDEX idx_Tile_XYZ ON Tiles(TileX,TileY,TileLevel);
        • DataCount is optional per-tile metadata that can be ignored.
    • Tile System / Projection Info:
      • Projection:
        • Web Mercator (Auxillary Sphere)
        • EPSG: 3857 (aka 900973)
      • Tile size: 
        • Standard 256x256 pixel tiles
      • Tile axis convention:  
        • Google Maps / Apple Maps / Bing Maps 
        • (upper-left is tile 0, 0)
    • File Format Info:
      • File Headers:
        • zlib stream compression headers
      • Uncompressed data:
        • Format: RAW
        • Headers: none
        • Byte Order: LSB (little endian)
        • Pixel Order:  Standard.
          • Row-ordered, starting with (0,0) in top left as first byte, and ending with (255,255) in bottom right as last byte
        • Channels: 1
        • NODATA value: 0
        • Bit Depth / Data Type:  16-bit unsigned integer
          • Exceptions:
            • 8-bit unsigned integer:
              • USGS/GSC NURE dose rate
              • NOAA Global Radiance
            • 32-bit floating point:
              • US DOE/NNSA Fukushima Cs-134
              • US DOE/NNSA Fukushima Cs-137
    • Value / Unit Translation:
      • Most datasets:
        • Dose rate in nSv/h as 16-bit unsigned integer; Pixel value = uSv/h * 1000.0
      • Exceptions
        • USGS/GSC NURE dose rate:  Pixel value = uSv/h * 870.0
        • NOAA Global Radiance:  N/A.  Did not record value mapping information.  Non-linear.  (gamma stretch / min / max were used)
        • US DOE / NNSA Fukushima Cs-134 / Cs-137:  Direct 1:1 value mapping.  Pixel value = uCi / m^2
  • Reuse Details:
    • Code:
      • 1.  Decompress tile using zlib ("INFLATE")
      • 2.  Use this byte array to create tile bitmap
      • 3.  Display directly or save as PNG, JPG, etc
      • Overall, this is actually relatively trivial, if you were creating dynamic map tiles in a C-type language to begin with.  zlib and sqlite are available on pretty much any platform.
    • Static Web Map / GIS System:
      • Not directly possible: RAW files are unsupported
      • (even if they were PNGs, they would appear as very dark/boring grayscale images unless modified further)
    • ImageJ:
      • ImageJ will read all decompressed Geiger Bot tiles as images with File -> Import -> RAW
      • A LUT can be very easily selected to better visualize the data once opened (though on a per-tile basis)

Background Subtracted Safecast Data for Japan

Download Safecast Background Subtracted Data (December 2012, Google Earth, 1.6 MB)

(Please note: these results should be considered preliminary, and an approximation.)

One of the potential uses of the background radiation data is to perform background subtraction on actual measurements, highlighting differences from natural levels -- and helping to identify possible contamination.

In order to determine if this was a valid approach and worth including in Geiger Bot, I performed a test of background subtraction using Safecast data in ArcMap.

[Background Subtraction] = [Measurement] - [Background]

This is shown in the image to the right.
The scale used is 0.03 - 0.30 uSv/h (linear).

The results and their correlation with Cs-137 aerial survey data seem to confirm the general viability of both the technique and previously interpolated background data.

This was however sensitive to the interpolation being used, which due to the nature of the source data was absolutely necessary in constructing the terrestrial dose rate background data.  To give credit to where it is due, I would not have been able to achieve the level of precision I did without Empirical Bayesian Kriging in ESRI's ArcGIS 10.1.

I do not have any plans to create, maintain or update web maps in general, but the background subtracted map is current data as of the time of this post.

Japan Natural Background Radiation Data

UPDATE:  I have completely redone this using EBK, or Empirical Bayesian Kriging (in ArcMap 10.1), to interpolate the terrestrial dose rate data.  This produces much better results due to some rather elaborate statistical models.

I have also created a Google Earth KMZ file that contains data points which you can download here.

While Japan's AIST has previously published a very similar map it did not include cosmic radiation and was therefore only a partial representation of the natural background dose rates you could expect to measure.

In summary, the approximate average natural background dose rate in Japan able to be measured with a sensor for gamma radiation is 0.08 uSv/h; 0.05 uSv/h is from terrestrial sources, and 0.03 uSv/h is from cosmic sources

This data will be included in a future version of Geiger Bot, both as a standard data layer visible on the map, as well as adding a "background subtraction" function to other Japan data layers.

Eventually, this may help to highlight measurements that differ significantly from expected natural background levels, as well as preventing false positives if an area has a higher amount of natural background radiation.

Data Processing and Methodology

These dose rate values have been calculated primarily from two parts:
  1. Terrestrial Dose Rate
    1. Geological sample data from AIST (産総研)
    2. Credit to Azby Brown for finding this
    3. Dose rate derived from geological data using methodology published by Duval, et al
    4. Empirical Bayesian Kriging in ArcMap 10.1 was used to predict values for all of Japan
  2. Cosmic Ray Dose Rate
    1. Digital Elevation Model (DTED0) from US NGA
    2. Dose rate calculated as per Duval, et al

Wait, what?  How is it possible to calculate the dose rate from some rocks and a relief map?

During the Cold War, there was a great deal of nuclear research performed by both the US and the Soviet Union.  One of the main concerns was always the resources-- where could uranium for weapons and energy be found?

Research found the easiest way to determine this was by using aircraft with scintillation counters which were shielded from cosmic radiation, measuring the terrestrial radiation from the earth -- which ended up almost entirely being due to gamma radiation emitted from uranium, thorium, potassium and their decay products.

So by using gamma spectroscopy from an aerial survey, it was possible to determine both the presence and concentration of uranium.

Through additional research these concentrations were able to be expressed in terms of how geologists had traditionally measured them in mineral samples (ppm, %K).  This allowed data gathered by aircraft to be appraised for potential value in ways that were already known.

So with this knowledge, one can work backwards from the concentrations of uranium, thorium, and potassium to calculate the terrestrial dose rate.  The approximate cosmic radiation dose rate can be derived more simply from elevation and latitude alone.

  1. The mineral samples collected are much fewer in number than the vast quantities of data points gathered in flight lines in aerial surveys in the previous "natural background" NURE dataset.  In fact, there are only about 3000 data points in total for the terrestrial data for Japan.  This means a greater likelihood of statistical error is present.
  2. Total natural background radiation -- for an individual -- is also considered to be comprised of additional factors, such as radon inhalation and internal exposure to isotopes in food and drink.  According to MEXT, for Japan these work out to be 0.09 uSv/h.  I have not seen figures for it and suspect it to be very small, but there is also some internal exposure from the decay of C-12 and K-40 within the human body itself.
My personal opinion is that radon being concentrated by inadequate ventilation in manmade structures is not wholly a "natural" source.

Regardless, for reference these are the values from the Wikipedia article on background radiation, converted to uSv/h from mSv/a and rounded to two decimal places.  (these are *not* what you should expect to measure with a Geiger or scintillation counter)

Average "Natural" Background Dose Rates (Wikipedia) 
 Inhalation, air (radon) 0.14 0.26 0.05
 Ingestion, food/drink 0.03 0.03 0.05
 Absorption, terrestrial 0.06 0.02 0.05
 Absorption, cosmic 0.05 0.04 0.03
Sum, "Natural" uSv/h 0.28 0.35 0.17

(The numbers do not appear to add up, but this only because the calculation itself was performed without rounding for greater accuracy.)

For Japan, the terrestrial and cosmic figures here approximately match the average values I found in creating the background data map -- 0.05 uSv/h terrestrial, 0.03 uSv/h cosmic, and a total of 0.08 uSv/h on average.  I was not aware of these figures prior to the data processing work I did above.