Unmanned Helicopter Monitoring in the Distribution Survey of Radioactive Substances
FY 2012 - FY 2016   The Ministry of Education, Culture, Sports, Science and Technology, and the Secretariat of the Nuclear Regulation Authority

This series of data was created based on measurement results of air dose rate of the unmanned helicopter monitoring in the Distribution Survey of Radioactive Substances conducted by the Ministry of...
This series of data was created based on measurement results of air dose rate of the unmanned helicopter monitoring in the Distribution Survey of Radioactive Substances conducted by the Ministry of Education, Culture, Sports, Science and Technology, and the Secretariat of the Nuclear Regulation Authority from FY 2012 to FY 2016.

Results of Air Dose Rate of the Unmanned Helicopter Monitoring within the 5 km Radius from the Fukushima Dai-ichi NPP ( from September 2016 to October 2016 )
  1. This data was created based on results of air dose rates measured by an unmanned helicopter within the 5 km radius of the Fukushima Dai-ichi NPP from September 2016 to October 2016 in the FY2016 Distribution Survey by NRA.
  2. Their flight altitude was 80 m above ground. The air dose rate at the ground surface is the averaged value of gamma dose in an 80 m diameter circle (varies by flight altitude) below the aircraft.
  3. The width of the track of the unmanned helicopter was 80 m.
  4. The flight velocity was approximately 8 m/s (28.8 km/h).
  5. Using a LaBr3(Ce) (lanthanum bromide) scintillation detector (ø 1.5" × 1.5" × 3 pcs), gamma ray from the ground and the direct and scattered gamma ray radiation from the NPP (counting rate), as well as energy spectra were measured every one second.
  6. Regarding air dose rates, a test site was established in the restricted area where the air dose rate barely varied in order to determine the conversion factor from gamma ray counting rate measured in the air to air dose rate on the ground. First, using a NaI scintillator, air dose rates at a height of 1 m above the ground within 100 m radius from the test site were measured and the averaged air dose rate was derived. Second, the gamma ray counting rate was obtained from a 80 m above the ground hovering unmanned helicopter at the test site, in addition the conversion factor CD between counting rate and air dose rate at a height of 1 m above the ground (cps/(μSv/h)) was obtained. Subsequently, the altitude correction function was derived from the gamma ray counting rates at every 10 m for a range between 10 m and 100 m above the ground from the hovering unmanned helicopter and then the attenuation coefficient by the air was calculated.Finally, air dose rates were obtained using the gamma ray counting rates which were obtained by an actual flight and by using the conversion factor CD and attenuation coefficient by the air above. (Note) The altitude of the unmanned helicopter was derived by subtracting the altitude in the Digital Elevation Model (10 m grids) issued by the Geospatial Information Authority of Japan from the GPS altitude of the unmanned helicopter.
  7. Regarding air dose rates, dead time was corrected because 1.8 - 2.0μs dead time had been found in the radiation measurement system of the unmanned helicopter when evaluated by irradiation equipment.
Results of Air Dose Rate of the Unmanned Helicopter Monitoring within the 5 km Radius from the Fukushima Dai-ichi NPP ( from September 2015 to October 2015 )
  1. This data was created based on results of air dose rates measured by an unmanned helicopter within the 5 km radius of the Fukushima Dai-ichi NPP from September 2015 to October 2015 in the FY2015 Distribution Survey by NRA.
  2. Their flight altitude was 80 m above ground. The air dose rate at the ground surface is the averaged value of gamma dose in an 80 m diameter circle (varies by flight altitude) below the aircraft.
  3. The width of the track of the unmanned helicopter was 80 m.
  4. The flight velocity was approximately 8 m/s (28.8 km/h).
  5. Using a LaBr3(Ce) (lanthanum bromide) scintillation detector (ø 1.5" × 1.5" × 3 pcs), gamma ray from the ground and the direct and scattered gamma ray radiation from the NPP (counting rate), as well as energy spectra were measured every one second.
  6. Regarding air dose rates, a test site was established in the restricted area where the air dose rate barely varied in order to determine the conversion factor from gamma ray counting rate measured in the air to air dose rate on the ground. First, using a NaI scintillator, air dose rates at a height of 1 m above the ground within 100 m radius from the test site were measured and the averaged air dose rate was derived. Second, the gamma ray counting rate was obtained from a 80 m above the ground hovering unmanned helicopter at the test site, in addition the conversion factor CD between counting rate and air dose rate at a height of 1 m above the ground (cps/(μSv/h)) was obtained. Subsequently, the altitude correction function was derived from the gamma ray counting rates at every 10 m for a range between 10 m and 100 m above the ground from the hovering unmanned helicopter and then the attenuation coefficient by the air was calculated.Finally, air dose rates were obtained using the gamma ray counting rates which were obtained by an actual flight and by using the conversion factor CD and attenuation coefficient by the air above. (Note) The altitude of the unmanned helicopter was derived by subtracting the altitude in the Digital Elevation Model (10 m grids) issued by the Geospatial Information Authority of Japan from the GPS altitude of the unmanned helicopter.
  7. Regarding air dose rates, dead time was corrected because 1.8 - 2.0μs dead time had been found in the radiation measurement system of the unmanned helicopter when evaluated by irradiation equipment.
Results of Air Dose Rate of the Unmanned Helicopter Monitoring within the 5 km Radius from the Fukushima Dai-ichi NPP ( from November 2014 to January 2015 )
  1. This data was created based on results of air dose rates measured by an unmanned helicopter within the 5 km radius of the Fukushima Dai-ichi NPP from November 13, 2014 to January 15, 2015 in the FY2014 Distribution Survey by NRA.
  2. Their flight altitude was 80 m above ground. The air dose rate at the ground surface is the averaged value of gamma dose in an 80 m diameter circle (varies by flight altitude) below the aircraft.
  3. The width of the track of the unmanned helicopter was 80 m.
  4. The flight velocity was approximately 8 m/s (28.8 km/h).
  5. Using a LaBr3(Ce) (lanthanum bromide) scintillation detector (ø 1.5" × 1.5" × 3 pcs), gamma ray from the ground and the direct and scattered gamma ray radiation from the NPP (counting rate), as well as energy spectra were measured every one second.
  6. Regarding air dose rates, a test site was established in the restricted area where the air dose rate barely varied in order to determine the conversion factor from gamma ray counting rate measured in the air to air dose rate on the ground. First, using a NaI scintillator, air dose rates at a height of 1 m above the ground within 100 m radius from the test site were measured and the averaged air dose rate was derived. Second, the gamma ray counting rate was obtained from a 80 m above the ground hovering unmanned helicopter at the test site, in addition the conversion factor CD between counting rate and air dose rate at a height of 1 m above the ground (cps/(μSv/h)) was obtained. Subsequently, the altitude correction function was derived from the gamma ray counting rates at every 10 m for a range between 10 m and 100 m above the ground from the hovering unmanned helicopter and then the attenuation coefficient by the air was calculated.Finally, air dose rates were obtained using the gamma ray counting rates which were obtained by an actual flight and by using the conversion factor CD and attenuation coefficient by the air above. (Note) The altitude of the unmanned helicopter was derived by subtracting the altitude in the Digital Elevation Model (10 m grids) issued by the Geospatial Information Authority of Japan from the GPS altitude of the unmanned helicopter.
  7. Regarding air dose rates, dead time was corrected because 1.8 - 2.0μs dead time had been found in the radiation measurement system of the unmanned helicopter when evaluated by irradiation equipment.
Results of Air Dose Rate of the Unmanned Helicopter Monitoring within the 5 km Radius from the Fukushima Dai-ichi NPP ( from June 2014 to July 2014 )
  1. This data was created based on results of air dose rates measured by an unmanned helicopter within the 5 km radius of the Fukushima Dai-ichi NPP from June 23, 2014 to July 22, 2014 in the FY2014 Distribution Survey by NRA.
  2. Their flight altitude was 80 m above ground. The air dose rate at the ground surface is the averaged value of gamma dose in an 80 m diameter circle (varies by flight altitude) below the aircraft.
  3. The width of the track of the unmanned helicopter was 80 m.
  4. The flight velocity was approximately 8 m/s (28.8 km/h).
  5. Using a LaBr3(Ce) (lanthanum bromide) scintillation detector (ø 1.5" × 1.5" × 3 pcs), gamma ray from the ground and the direct and scattered gamma ray radiation from the NPP (counting rate), as well as energy spectra were measured every one second.
  6. Regarding air dose rates, a test site was established in the restricted area where the air dose rate barely varied in order to determine the conversion factor from gamma ray counting rate measured in the air to air dose rate on the ground. First, using a NaI scintillator, air dose rates at a height of 1 m above the ground within 100 m radius from the test site were measured and the averaged air dose rate was derived. Second, the gamma ray counting rate was obtained from a 80 m above the ground hovering unmanned helicopter at the test site, in addition the conversion factor CD between counting rate and air dose rate at a height of 1 m above the ground (cps/(μSv/h)) was obtained. Subsequently, the altitude correction function was derived from the gamma ray counting rates at every 10 m for a range between 10 m and 100 m above the ground from the hovering unmanned helicopter and then the attenuation coefficient by the air was calculated.Finally, air dose rates were obtained using the gamma ray counting rates which were obtained by an actual flight and by using the conversion factor CD and attenuation coefficient by the air above. (Note) The altitude of the unmanned helicopter was derived by subtracting the altitude in the Digital Elevation Model (10 m grids) issued by the Geospatial Information Authority of Japan from the GPS altitude of the unmanned helicopter.
  7. Regarding air dose rates, dead time was corrected because 1.8 - 2.0μs dead time had been found in the radiation measurement system of the unmanned helicopter when evaluated by irradiation equipment.
Results of Air Dose Rate of the Unmanned Helicopter Monitoring within the 5 km Radius from the Fukushima Dai-ichi NPP ( From November 2013 to January 2014 )
  1. This data was created based on results of air dose rates measured by an unmanned helicopter within the 5 km radius of the Fukushima Dai-ichi NPP from November 19, 2013 to January 7, 2014 in the FY2013 Distribution Survey by NRA.
  2. Their flight altitude was 80 m above ground. The air dose rate at the ground surface is the averaged value of gamma dose in an 80 m diameter circle (varies by flight altitude) below the aircraft.
  3. The width of the track of the unmanned helicopter was 80 m.
  4. The flight velocity was approximately 8 m/s (28.8 km/h).
  5. Using a LaBr3(Ce) (lanthanum bromide) scintillation detector (ø 1.5" × 1.5" × 3 pcs), gamma ray from the ground and the direct and scattered gamma ray radiation from the NPP (counting rate), as well as energy spectra were measured every one second.
  6. Regarding air dose rates, a test site was established in the restricted area where the air dose rate barely varied in order to determine the conversion factor from gamma ray counting rate measured in the air to air dose rate on the ground. First, using a NaI scintillator, air dose rates at a height of 1 m above the ground within 100 m radius from the test site were measured and the averaged air dose rate was derived. Second, the gamma ray counting rate was obtained from a 80 m above the ground hovering unmanned helicopter at the test site, in addition the conversion factor CD between counting rate and air dose rate at a height of 1 m above the ground (cps/(μSv/h)) was obtained. Subsequently, the altitude correction function was derived from the gamma ray counting rates at every 10 m for a range between 10 m and 100 m above the ground from the hovering unmanned helicopter and then the attenuation coefficient by the air was calculated.Finally, air dose rates were obtained using the gamma ray counting rates which were obtained by an actual flight and by using the conversion factor CD and attenuation coefficient by the air above. (Note) The altitude of the unmanned helicopter was derived by subtracting the altitude in the Digital Elevation Model (10 m grids) issued by the Geospatial Information Authority of Japan from the GPS altitude of the unmanned helicopter.
  7. Regarding air dose rates, dead time was corrected because 1.8 - 2.0μs dead time had been found in the radiation measurement system of the unmanned helicopter when evaluated by irradiation equipment.
Results of Air Dose Rate of the Unmanned Helicopter Monitoring within the 5 km Radius from the Fukushima Dai-ichi NPP ( From June 2013 to July 2013 )
  1. This data was created based on results of air dose rates measured by an unmanned helicopter within the 5 km radius of the Fukushima Dai-ichi NPP from June 6, 2013 to July 31, 2013 in the FY2013 Distribution Survey by NRA.
  2. Their flight altitude was 80 m above ground. The air dose rate at the ground surface is the averaged value of gamma dose in an 80 m diameter circle (varies by flight altitude) below the aircraft.
  3. The width of the track of the unmanned helicopter was 80 m.
  4. The flight velocity was approximately 8 m/s (28.8 km/h).
  5. Using a LaBr3(Ce) (lanthanum bromide) scintillation detector (ø 1.5" × 1.5" × 3 pcs), gamma ray from the ground and the direct and scattered gamma ray radiation from the NPP (counting rate), as well as energy spectra were measured every one second.
  6. Regarding air dose rates, a test site was established in the restricted area where the air dose rate barely varied in order to determine the conversion factor from gamma ray counting rate measured in the air to air dose rate on the ground. First, using a NaI scintillator, air dose rates at a height of 1 m above the ground within 100 m radius from the test site were measured and the averaged air dose rate was derived. Second, the gamma ray counting rate was obtained from a 80 m above the ground hovering unmanned helicopter at the test site, in addition the conversion factor CD between counting rate and air dose rate at a height of 1 m above the ground (cps/(μSv/h)) was obtained. Subsequently, the altitude correction function was derived from the gamma ray counting rates at every 10 m for a range between 10 m and 100 m above the ground from the hovering unmanned helicopter and then the attenuation coefficient by the air was calculated.Finally, air dose rates were obtained using the gamma ray counting rates which were obtained by an actual flight and by using the conversion factor CD and attenuation coefficient by the air above. (Note) The altitude of the unmanned helicopter was derived by subtracting the altitude in the Digital Elevation Model (10 m grids) issued by the Geospatial Information Authority of Japan from the GPS altitude of the unmanned helicopter.
  7. Regarding air dose rates, dead time was corrected because 1.8 - 2.0μs dead time had been found in the radiation measurement system of the unmanned helicopter when evaluated by irradiation equipment.
Results of Air Dose Rate of the Second Unmanned Helicopter Monitoring within the 3 km Radius from the Fukushima Dai-ichi NPP ( Decay correction: March 20, 2013 )
  1. This data was created based on the results of air dose rates measured from January 27, 2013 to March 7, 2013 in the Third Distribution Survey by MEXT.
  2. Their flight altitudes were from 50 to 80 m above ground. The air dose rate at the ground surface is the averaged value of gamma dose in a roughly 50 m to 80 m diameter circle (varies by flight altitude) below the unmanned helicopter.
  3. The widths of the track of the unmanned helicopter were 50 m or 80 m.
  4. The flight velocity was approximately 8 m/s (28.8 km/h).
  5. Using a LaBr3(Ce) (lanthanum bromide) scintillation detector (ø1.5" × 1.5" × 3 pcs), gamma ray from the ground and the direct and scattered gamma ray radiation from the NPP (counting rate), as well as energy spectra were measured every one second.
  6. Regarding air dose rates, we established one test line within the target area of this monitoring survey, and first ascertaining trends at each altitude in counting rate (cps) measured in the air on the test line (10 to 100 m) (altitude correction function), and then based on the counting rate at a certain altitude above the test line and air dose rates (µSv/h) at a height of 1 m above the ground measured around the test line using NaI scintillators, obtaining the conversion factor between counting rate and air dose rate at a height of 1 m above the ground (cps/(µSv/h)). Air dose rates 1 m above the ground were calculated by converting counting rates measured in the air above each monitoring point, using said altitude correction function and the conversion factor. The data include air dose rates by natural radionuclides.
Results of Air Dose Rate Measurement in Riverbank by Unmanned Helicopter ( Decay correction: January 31, 2013 )
  1. This data was created based on the results of air dose rates measured from January 8, 2013 to January 31, 2013 for Abukumagawa river basin (Miyagi Prefecture) and from October 31, 2012 to November 7, 2012 for Udagawa river basin (Soma City, Fukushima Prefecture) in the Third Distribution Survey by MEXT.
  2. Their flight altitudes were from 50 to 80 m above ground. The air dose rate at the ground surface is the averaged value of gamma dose in a roughly 50 m to 80 m diameter circle (varies by flight altitude) below the unmanned helicopter.
  3. The widths of the track of the unmanned helicopter were 50 m or 80 m.
  4. The flight velocity was approximately 8 m/s (28.8 km/h).
  5. Using a LaBr3(Ce) (lanthanum bromide) scintillation detector (ø1.5" × 1.5" × 3 pcs), gamma ray from the ground and the direct and scattered gamma ray radiation from the NPP (counting rate), as well as energy spectra were measured every one second.
  6. Regarding air dose rates, we established one test line within the target area of this monitoring survey, and first ascertaining trends at each altitude in counting rate (cps) measured in the air on the test line (10 to 100 m) (altitude correction function), and then based on the counting rate at a certain altitude above the test line and air dose rates (µSv/h) at a height of 1 m above the ground measured around the test line using NaI scintillators, obtaining the conversion factor between counting rate and air dose rate at a height of 1 m above the ground (cps/(µSv/h)). Air dose rates 1 m above the ground were calculated by converting counting rates measured in the air above each monitoring point, using said altitude correction function and the conversion factor. The data include air dose rates by natural radionuclides.
Results of Air Dose Rate of the First Unmanned Helicopter Monitoring within the 3 km Radius from the Fukushima Dai-ichi NPP ( Decay correction: October 20, 2012 )
  1. This data was created based on results of air dose rates measured from October 2, 2012 to October 20, 2012 in the Third Distribution Survey by MEXT.
  2. Their flight altitudes were from 50 to 80 m above ground. The air dose rate at the ground surface is the averaged value of gamma dose in a roughly 50 m to 80 m diameter circle (varies by flight altitude) below the aircraft.
  3. The widths of the track of the unmanned helicopter were 50 m or 80 m.
  4. The flight velocity was approximately 8 m/s (28.8 km/h)
  5. Using a LaBr3(Ce) (lanthanum bromide) scintillation detector (ø1.5" × 1.5" × 3 pcs), gamma ray from the ground and the direct and scattered gamma ray radiation from the NPP (counting rate), as well as energy spectra were measured every one second.
  6. Regarding air dose rates, we established one test line within the target area of this monitoring survey, and first ascertaining trends at each altitude in counting rate (cps) measured in the air on the test line (10 to 100 m) (altitude correction function), and then based on the counting rate at a certain altitude above the test line and air dose rates (µSv/h) at a height of 1 m above the ground measured around the test line using NaI scintillators, obtaining the conversion factor between counting rate and air dose rate at a height of 1 m above the ground (cps/(µSv/h)). Air dose rates 1 m above the ground were calculated by converting counting rates measured in the air above each monitoring point, using said altitude correction function and the conversion factor. The data include air dose rates by natural radionuclides.
Publicly available data collected from the website of the relevant organizations and converted into CSV, XML, and KML formats that were easy to use.

Results of Air Dose Rate of the First Unmanned Helicopter Monitoring within the 3 km Radius from the Fukushima Dai-ichi NPP ( Decay correction: October 20, 2012 )
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CSV files that have common item names over different survey projects for comparison analyses.

Results of Air Dose Rate of the Unmanned Helicopter Monitoring within the 5 km Radius from the Fukushima Dai-ichi NPP ( from September 2016 to October 2016 )
Results of Air Dose Rate of the Unmanned Helicopter Monitoring within the 5 km Radius from the Fukushima Dai-ichi NPP ( from September 2015 to October 2015 )
Results of Air Dose Rate of the Unmanned Helicopter Monitoring within the 5 km Radius from the Fukushima Dai-ichi NPP ( from November 2014 to January 2015 )
Results of Air Dose Rate of the Unmanned Helicopter Monitoring within the 5 km Radius from the Fukushima Dai-ichi NPP ( from June 2014 to July 2014 )
Results of Air Dose Rate of the Unmanned Helicopter Monitoring within the 5 km Radius from the Fukushima Dai-ichi NPP ( From November 2013 to January 2014 )
Results of Air Dose Rate of the Unmanned Helicopter Monitoring within the 5 km Radius from the Fukushima Dai-ichi NPP ( From June 2013 to July 2013 )
Results of Air Dose Rate of the Second Unmanned Helicopter Monitoring within the 3 km Radius from the Fukushima Dai-ichi NPP ( Decay correction: March 20, 2013 )
Results of Air Dose Rate of the First Unmanned Helicopter Monitoring within the 3 km Radius from the Fukushima Dai-ichi NPP ( Decay correction: October 20, 2012 )