AEROMAGNETIC SURVEY
This is a continuation of the report of aeromagnetic surveys by the Hydrographic andOceanographic Department. The results of three surveys, Kozu-shima,Suwanosejima andNakanoshima carried out in 2009 and 2010 are presented in this report.
Key word: aeromagnetic survey.

1. Survey
The aircraft used for the survey was YS-11 which had been remodeled so that its flying range beextended and that magnetic survey be carried out on board. The aircraft was equipped with atail-stinger of non-magnetic plastics of 1.5 meters long at the rear of the fuselage. The instruments
used for the survey are a proton magnetometer and GPS receiver.
The proton magnetometer measured geomagnetic total intensity once per two seconds with anaccuracy of ±1 nano-tesla.

2. Data processing and results
The measured total intensity include components of external field variation. The correction of
the external field variation was carried out based on the continuous magnetic observations at areference magnetic observatory close to the survey area.
For calculations of magnetic anomaly, the IGRF2005 and IGRF2010 was used as the core fieldmodel in accordance with the recommendation of the IAGA.
The details on the compiled aeromagnetic surveys are listed in Table 1.
Fig. 1~3 show the magnetic anomaly of the total intensity.
Reduction and compilation of this report have been made by K.Ogata,K.Onodera and K.Koyama
belong to Geodesy and Geophysics Office.

Reference
Data Report of Hydrographic Observations, Series of Astronomy and Geodesy, No.31, 1997,
Data Report of Hydrographic Observations, Series of Astronomy and Geodesy, No.32, 1998,
Data Report of Hydrographic Observations, Series of Astronomy and Geodesy, No.33, 1999,
Data Report of Hydrographic Observations, Series of Astronomy and Geodesy, No.35, 2001,
Data Report of Hydrographic Observations, Series of Astronomy and Geodesy, No.36, 2002,
Data Report of Hydrographic Observations, Series of Astronomy and Geodesy, No.37, 2003
Data Report of Hydrographic Observations, Series of Astronomy and Geodesy, No.38, 2004
AEROMAGNETIC SURVEY(2003-2008)

Table 1. Details on the compiled aeromagnetic surveys

Cruise index
09KOZUArea
Kozu-shima
PeriodDec. 23-25 2009
Aircraft
YS-11
Flight Altitude
1,100 mMagnetometer
M-123
Positioning
GPS
Track lines
0.125~1 naut. Mile N-S
Anomaly map
Fig. 1
Scale of original map
1/50,000
Map projection
TM
Reference MagneticKakioka
Observatory(36ﾟ13.'9 N, 140ﾟ11.'2 E)
Reference value for an
46,449 nT
External field correction
Core field model
IGRF2005
Contour interval
25nT
Epoch year
2009.12

Cruise index
10NA
Area
Nakanoshima
PeriodOct. 21 2010
Aircraft
YS-11
Flight Altitude
1,330 mMagnetometer
M-123
Positioning
GPS
Track lines
0.5 naut. Mile N-S
Anomaly map
Fig. 3
Scale of original map
1/50,000
Map projection
TM
Reference Magnetic
KanoyaObservatory(31ﾟ25.’2 N, 130ﾟ52.’9 E)
Reference value for an
46,392 nT
External field correction
Core field model
IGRF2010
Contour interval
25nT
Epoch year
2010.1009SU
SuwanosejimaDec. 7-8 2009
YS-11
1,100 mM-123
GPS
0.5~1 naut. Mile N-S
Fig. 2
1/50,000
TMKanoya(31ﾟ25.’2 N, 130ﾟ52.’9 E)
46,378 nT
IGRF2005
25nT
2009.12Kozu-shima

Fig.1 Geomagnetic total intensity anomaly map in and around Kozu-shima.
(Coastline based on material Geographical Survey Institute)Fig.2 Geomagnetic total intensity anomaly map in and around Suwanosejima.
(Land area based on material Geographical Survey Institute)Fig.3 Geomagnetic total intensity anomaly map in and around Nakanoshima.
(Land area based on material Geographical Survey Institute)