AEROMAGNETIC SURVEY
This is a continuation of the report of aeromagnetic surveys by the Hydrographic andOceanographic Department. The results of ten surveys, Kita-Fukutokutai, Yokoatejima,Satsuma-Iojima, Fukutoku-Okanoba, Izu-Oshima, Io-Torishima, Ioto, Miyakejima, Izu-Oshima, andKuchinoerabujima carried out in 2003 and 2008 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 IGRF2000 and IGRF2005 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. 1~10 show the magnetic anomaly of the total intensity.
Reduction and compilation of this report have been made by S.Kato and K.Koyama belong toGeodesy 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

Table 1. Details on the compiled aeromagnetic surveys

Cruise index
Area
PeriodAircraft
Flight Altitude
Magnetometer
Positioning
Track lines

03KIF
04YO
Kita-Fukutokutai
Yokoatejima
Mar. 11 2003
Nov. 11 2004
YS-11
YS-11
1,000 feet
2,200 feet
M-123
M-123
GPSGPS
1 naut. Mile N-S and E-W 0.5~1 naut. Mile N-S andE-W
Fig. 1
Fig. 2
1/50,000
1/50,000
TMTM
Hachijo
Kanoya(33ﾟ04.’6 N, 139ﾟ49.’3 E)(31ﾟ25.’2 N, 130ﾟ52.’9 E)
45,208nT
45,215nT

Anomaly map
Scale of original map
Map projection
Reference MagneticObservatory
Reference value for anExternal field correction
Core field model
IGRF2000
Contour interval
50nT
Epoch year
2003.1

Cruise index
05SAArea
Satsuma-Iojima
PeriodNov. 7 2005
Aircraft
YS-11
Flight Altitude4,600 feet
Magnetometer
M-123
Positioning
GPS
Track lines
0.5 naut. Mile E-W
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
46,320nT
External field correction
Core field model
IGRF2005
Contour interval
20nT
Epoch year
2005.11

IGRF200025nT
2004.1006FU
Fukutoku-Okanoba
Mar. 15 2006
YS-11
1,200 feetM-123
GPS
0.5 naut. Mile N-S
Fig. 4
1/50,000
TM
Hachijo(33ﾟ04.’6 N, 139ﾟ49.’3 E)
46,384nT
IGRF2005
100nT
2006.3

Cruise index
Area
PeriodAircraft
Flight Altitude
Magnetometer
Positioning
Track lines

06OS
Izu-Oshima
Feb. 24 2006
YS-11
3,800 feet
M-123
GPS
0.25~0.5 naut. Mile N-S

Anomaly map
Fig. 5
Scale of original map
1/50,000
Map projection
TM
Reference Magnetic
HachijoObservatory(33ﾟ04.’6 N, 139ﾟ49.’3 E)
Reference value for an
45,213nT
External field correction
Core field model
IGRF2005
Contour interval
100nT
Epoch year
2006.2

Cruise index
Area
PeriodAircraft
Flight Altitude
Magnetometer
Positioning
Track lines

07IO
Ioto
Jan. 23 2007
YS-11
2,200 feet
M-123
GPS
0.25 naut. Mile N-S

Anomaly map
Fig. 7
Scale of original map
1/50,000
Map projection
TM
Reference Magnetic
HachijoObservatory(33ﾟ04.’6 N, 139ﾟ49.’3 E)
Reference value for an
45,222nT
External field correction
Core field model
IGRF2005
Contour interval
100nT
Epoch year
2007.106IT
Io-Torishima
Oct. 5 2006
YS-11
1,300 feet
M-123
GPS
0.25~0.5 naut. Mile N-S andE-W
Fig. 6
1/100,000TMKanoya(31ﾟ25.’2 N, 130ﾟ52.’9 E)
46,390nT
IGRF2005
25nT
2006.1007MI
Miyakejima
Jul. 10 2007
YS-11
4,800 feet
M-123
GPS
0.5~1 naut. Mile N-S andE-W
Fig. 81/100,000
TMHachijo(33ﾟ04.’6 N, 139ﾟ49.’3 E)
45,238nT
IGRF2005
50nT
2007.7

Cruise index
08OS
Area
Izu-Oshima
PeriodJul. 19 2008
Aircraft
YS-11
Flight Altitude
3,800 feet
Magnetometer
M-123
Positioning
GPSTrack lines
0.5 naut. Mile N-S
Anomaly map
Fig. 9
Scale of original map
1/50,000
Map projection
TMReference Magnetic
HachijoObservatory(33ﾟ04.’6 N, 139ﾟ49.’3 E)
Reference value for an
45,254nT
External field correction
Core field model
IGRF2005
Contour interval
100nT
Epoch year
2008.709KU
Kuchinoerabujima
Feb. 4 2009
YS-11
2,400 feet
M-123
GPS
0.25~1 naut. Mile N-S
Fig. 10
1/50,000
TMKanoya(31ﾟ25.’2 N, 130ﾟ52.’9 E)
46,310nT
IGRF2005
25nT
2009.2

Fig.1 Geomagnetic total intensity anomaly map in and around Kita-Fukutokutai.

Fig.2 Geomagnetic total intensity anomaly map in and around Yokoatejima.

Fig.3 Geomagnetic total intensity anomaly map in and around Satsuma-Iojima.

Fig.4 Geomagnetic total intensity anomaly map in and around Fukutoku-Okanoba.

Fig.5 Geomagnetic total intensity anomaly map in and around Izu-Oshima

Fig.6 Geomagnetic total intensity anomaly map in and around Io-Torishima

Fig.7 Geomagnetic total intensity anomaly map in and around Ioto.

Fig.8 Geomagnetic total intensity anomaly map in and around Miyakejima.

Fig.9 Geomagnetic total intensity anomaly map in and around Izu-Oshima

Fig.10 Geomagnetic total intensity anomaly map in and around Kuchinoerabujima