Total magnetic intensity (TMI) data measures variations in the intensity of the Earth magnetic field caused by the contrasting content of rock-forming minerals in the Earth crust. Magnetic anomalies can be either positive (field stronger than normal) or negative (field weaker) depending on the susceptibility of the rock. The data are processed via standard methods to ensure the response recorded is that due only to the rocks in the ground. The results produce datasets that can be interpreted to reveal the geological structure of the sub-surface. The processed data is checked for quality by GA geophysicists to ensure that the final data released by GA are fit-for-purpose. This magnetic grid has a cell size of 0.001 degrees (approximately 110m). The data used to produce this grid was acquired in 2000 by the WA Government, and consisted of 10950.0 line-kilometres of data at 400.0m line spacing and 80.0m terrain clearance.

Total magnetic intensity (TMI) data measures variations in the intensity of the Earth magnetic field caused by the contrasting content of rock-forming minerals in the Earth crust. Magnetic anomalies can be either positive (field stronger than normal) or negative (field weaker) depending on the susceptibility of the rock. The data are processed via standard methods to ensure the response recorded is that due only to the rocks in the ground. The results produce datasets that can be interpreted to reveal the geological structure of the sub-surface. The processed data is checked for quality by GA geophysicists to ensure that the final data released by GA are fit-for-purpose. This magnetic grid has a cell size of 0.0005 degrees (approximately 50m). The data used to produce this grid was acquired in 2000 by the SA Government, and consisted of 8650.0 line-kilometres of data at 300.0m line spacing and 80.0m terrain clearance.

This image is a greyscale image of the Total Magnetic Intensity (TMI) Anomaly Image of Australia with Variable Reduction to Pole (VRTP). Total magnetic intensity (TMI) data measures variations in the intensity of the Earth magnetic filed caused by the contrasting content of rock-forming minerals in the Earth crust. Magnetic anomalies can be either positive (field stronger than normal) or negative (field weaker) depending on the susceptibility of the rock. A variable reduction to Pole is aimed at locating magnetic anomalies exactly above their source bodies and without any distortion. The image is created from the 2019 variable reduction to Pole of the TMI grid with a grid cell size of ~3 seconds of arc (approximately 80 m). This image only includes airborne-derived TMI data for onshore and near-offshore continental areas. The image provides a better interpretation of the magnetic data by giving an accurate location of magnetic source bodies.

Total Magnetic Intensity colour composite image 2015 The image was created from the Total Magnetic Intensity Grid 2015 - sixth edition. This image has a cell size of ~3 seconds of arc (approximately 80 m) and has been image enhanced for optimal display in Hue-Saturation-Intensity (HSI). This image only includes airborne-derived TMI data for onshore and near-offshore continental areas. Since the fifth edition was released in 2010 data from 41 new surveys have been added to the database, acquired mainly by the State and Territory Geological Surveys. It is estimated that 31 500 000 line-kilometres of survey data were acquired to produce the grid data, 4 500 000 line-kilometres more than for the previous edition.

Efforts are underway to digitally preserve seismograms, magnetograms and geomagnetic absolute observations from Australian observatories. These datasets are stored in original paper and film form and although they are available on request they are not easily discoverable or available at short notice to the public. The retrieval of analogue media is both time-consuming and labour-intensive and can cause further damage to deteriorating records. In this poster, we detail preserved examples of the handwritten records, microfilm, as well as original paper records dating back to 1959 for magnetograms from Wilkes Geomagnetic Observatory, and to 1902 for seismograms from Melbourne Observatory. Different generations of collected data have challenges associated with the preservation efforts, including; legibility, data compression algorithms, stability of the original medium and associated metadata. Additionally, costs and expertise required to create digital copies varies greatly between the different original mediums of data recordings. Our ongoing efforts have prioritised the preservation of the original analogue data through creation of digital copies before the record suffers from further deterioration, and, making those digital records publicly accessible through Geoscience Australia’s data servers to improve discoverability. Long term efforts following this will then be focused on digitisation for use with modern data analysis techniques. Presented at the 2022 Australian Earthquake Engineering Society (AEES) Conference.

This dataset contains scanned geomagnetic magnetogram records from Wilkes Geomagnetic Observatory. Files names delineate the observatory, observation year, type of data, month range, folder and page. e.g. TOO 1985 GRAM - JUL - AUG - 73_00031 (TOO: Toolangi Observatory)(1985: Year)(GRAM: Magnetogram)(JUL - AUG: month range)(73_00031: Folder and page). Files are stored as station and year based PDF and individual tiff files per page.

Absolute observations of the vector geomagnetic field were made 1.60 m above ground level at the marked centre of Darwin International Airport (DIA) compass swing site on taxi-way C4 on Monday 19 November 2012 (coordinated universal time). The observations were made during geomagnetic quiet conditions. The average observed values were +3.46°, -39.65° and 46285 nT in declination, inclination and total magnetic intensity respectively. When corrected to average undisturbed values of the field, using data from the Kakadu Geomagnetic Observatory to derive corrections, the adopted normal field values are +3.53°, -39.65°, 46272 nT in declination, inclination and total magnetic intensity respectively. Hence the magnetic declination at 1.60 m above ground level at the centre of the DIA compass swing site in November 2012 is +3.53°. This value has changed by -0.24° since it was previously determined in December 2007. Applying the November 2012 adopted value of magnetic declination to the true azimuth from the centre of the swing site to the aerodrome reference point gives the magnetic bearing from the centre of the swing site to the ARP of 123.766°.

This dataset contains scanned geomagnetic absolute observation records from Australian Geomagnetic Observatory: Kakadu (KDU). Files names delineate the observatory, observation year, type of form and folder. e.g. KDU2000OBS_19 (KDU: Kakadu Observatory)(2000: Year)(OBS: Observation Form)(19: Folder). Files are stored as station and year based PDF and individual tiff files per page.

This dataset contains scanned geomagnetic absolute observation records from Australian Geomagnetic Observatories. Files names delineate the observatory, observation year, type of form and folder. e.g. CTA2000OBS_19 (CTA: Charters Towers Observatory)(2000: Year)(OBS: Observation Form)(19: Folder). Files are stored as station and year based PDF and individual tiff files per page.

Total magnetic intensity (TMI) data measures variations in the intensity of the Earth magnetic field caused by the contrasting content of rock-forming minerals in the Earth crust. Magnetic anomalies can be either positive (field stronger than normal) or negative (field weaker) depending on the susceptibility of the rock. The data are processed via standard methods to ensure the response recorded is that due only to the rocks in the ground. The results produce datasets that can be interpreted to reveal the geological structure of the sub-surface. The processed data is checked for quality by GA geophysicists to ensure that the final data released by GA are fit-for-purpose. This magnetic grid has a cell size of 0.002 degrees (approximately 210m). The data used to produce this grid was acquired in UNKNOWN by the UNKNOWN Government, and consisted of UNKNOWN line-kilometres of data at 200.0m line spacing and UNKNOWNm terrain clearance.