Date (Creation)

2019-12-04

Date (Revision)

2019-12-04

Date (Publication)

2019-12-04

Date (released)

2019-12-04

Edition

1.0

Unique resource identifier

https://doi.org/10.5285/5de1230c-33f5-4586-821b-e6c40316d6bd

Codespace

doi

Unique resource identifier

GB/NERC/BAS/PDC/01278

Codespace

https://data.bas.ac.uk/

Other citation details

Please cite this item as: Jones, P., Ferraccioli, F., & Smith, A. (2020). Processed line aerogravity data over Ellsworth Land region (2001) (Version 1.0) [Data set]. UK Polar Data Centre, Natural Environment Research Council, UK Research & Innovation. https://doi.org/10.5285/5de1230c-33f5-4586-821b-e6c40316d6bd

Credit

No credit.

Status

Completed

Point of contact

Organisation name	Individual name	Electronic mail address	Role
British Antarctic Survey	Jones, P.		Author
British Antarctic Survey	Ferraccioli, Fausto		Author
British Antarctic Survey	Smith, Andrew		Author
NERC EDS UK Polar Data Centre		PDCServiceDesk@bas.ac.uk	Point of contact

Maintenance and update frequency

As needed

Maintenance note

Completed

Global Change Master Directory (GCMD) Science Keywords

• EARTH SCIENCE > Solid Earth > Geodetics/Gravity > Gravity

Theme

• Aerogeophysical

• Antarctic

• Gravity

Place

• Ellsworth Land Antarctica

GEMET - INSPIRE themes, version 1.0

• Geology

Access constraints

Other restrictions

Other constraints

no limitations to public access

Access constraints

Other restrictions

Other constraints

no limitations

Use constraints

License

Other constraints

Open Government Licence v3.0

Use constraints

Other restrictions

Other constraints

This data is governed by the NERC Data Policy: https://www.ukri.org/who-we-are/nerc/our-policies-and-standards/nerc-data-policy/

Use constraints

Other restrictions

Other constraints

Further by downloading this data the user acknowledges that they agree with the NERC data policy (), and the following conditions:

1. To cite the data in any publication as follows:

Jones, P., Ferraccioli, F., & Smith, A. (2020). Processed line aerogravity data over Ellsworth Land region (2001) [Data set]. UK Polar Data Centre, Natural Environment Research Council, UK Research & Innovation. https://doi.org/10.5285/5DE1230C-33F5-4586-821B-E6C40316D6BD

2. The user recognizes the limitations of data. Use of the data is at the users' own risk, and there is no warranty as to the quality or accuracy of any data, or the fitness of the data for your intended use. The data are not necessarily fully quality assured and cannot be expected to be free from measurement uncertainty, systematic biases, or errors of interpretation or analysis, and may include inaccuracies in error margins quoted with the data.

Unique resource identifier

url

Codespace

url

Association Type

Cross reference

Unique resource identifier

url

Codespace

url

Association Type

Cross reference

Unique resource identifier

doi

Codespace

doi

Association Type

Cross reference

Unique resource identifier

doi

Codespace

doi

Association Type

Cross reference

Unique resource identifier

url

Codespace

url

Association Type

Cross reference

Spatial representation type

Text, table

Language

English

Character set

UTF8

Topic category

• Geoscientific information

Begin date

2001-11-21

End date

2001-12-11

Supplemental Information

It is recommended that careful attention be paid to the contents of any data, and that the author be contacted with any questions regarding appropriate use. If you find any errors or omissions, please report them to polardatacentre@bas.ac.uk.

Title

European Petroleum Survey Group (EPSG) Geodetic Parameter Registry

Date (Publication)

2008-11-12

Cited responsible party

Organisation name	Individual name	Electronic mail address	Role
European Petroleum Survey Group		EPSGadministrator@iogp.org	Publisher

Unique resource identifier

urn:ogc:def:crs:EPSG::3031

Version

6.18.3

Hierarchy level

Dataset

Statement

Methodology:

Aerogravity measurements were acquired with a modified LaCoste and Romberg air/sea gravimeter. The aircraft acceleration was calculated from dual frequency, carrier phase measurements using geodetic receivers. Free-air gravity anomalies were calculated, and a low-pass filter was applied to the data. Cross-over analysis indicates the free-anomaly field is accurate to 3.7 mGals for wavelengths greater than 9 km.

Processing steps:

1/ Calculate observed gravity.

True spring tension (ST_real) is calculated from the posted spring tension (ST) correcting for the fact that for this survey the true spring tension approaches the posted value at 38 mGal per second.

Beam velocity (Beam_vel) is derived from raw beam position (RB) assuming a centred difference approximation.

Relative gravity (rec_grav) = (Spr_tens_real+((beam_vel)*k_fac)+CC)*scale_value, k_fac=30, meter scale value =0.9966.

Still readings (Still) are in mGal and were calculating assuming a 2nd order best fit to the approximately linear drift of the meter observed at the tie down points.

Airborne absolute gravity values (Abs_grav) = Rec_grav- Still + Base

2/ Corrections to derive free air anomalies (disturbances).

Vertical acceleration (VaccCor) is calculated as 2nd derivative of flight altitude (Height_WGS1984), with a 3 point mean filter applied after differencing to reduce short wavelength noise.

Eotvos correction (EotvosCor) follows (Harlan, 1968).

Latitude correction (LatCor) = 978.03185(1+0.005278895 sin2Lat- 0.000023462 sin4Lat) (IUGG 1967).

Free air correction (FaCor) = 0.3086*Height_WGS1984. NOTE subsequent free air values are defined as gravity disturbances in geodesy, as they are referred to the ellipsoid (Hackney and Featherstone, 2003).

Horizontal acceleration correction (HaccCor). For this survey the approximation of (Swain, 1996) was used, assuming a damping factor of 0.707, and a platform period of 4 minutes.

3/ Free air anomaly and filtering.

Free air anomaly (Free_air) = Abs_grav-VaccCor+EotvosCor+FaCor-LatCor-(0.5*HaccCor)

Filtered free air anomaly (FAA_filt) used 9 km 1/2 wavelength space domain kernel filter (Holt et al., 2006).

Final free air data (FAA_clip) was produced by manually masking turns, start and end of lines, and other regions of noisy data.

Levelling correction (level_cor) includes both statistical (line and tie) and microleveling (line only) of free air data.

FAA_level includes data after levelling.

Upward continued free air anomaly (FAA_1976m) was produced by upward continuing free air data from the collected flight altitude to 1976 m.

Channel description:

Basic Channels

Date UTC date (YYYY/MM/DD)

Time UTC time (HH:MM:SS.SS)

FlightID Sequential flight number and survey ID e.g. W12

Line_name Line Number e.g. LW200.1:12

Lon Longitude WGS 1984

Lat Latitude WGS 1984

x x projected meters*

y y projected meters*

Height_WGS1984 Aircraft altitude (meters) in WGS 1984

Raw gravity Channels

ST Spring Tension (meter units)

CC Cross Coupling (meter units)

RB Raw beam position (Mv)

XACC Cross axis accelerometer (Mv)

LACC Long axis accelerometer (Mv)

Still Airborne meter still reading value (mGal)

Base Absolute gravity reference, from land gravity (mGal)

Calculation Channels

St_real True Spring tension value (meter units)

Beam_vel Gravity meter beam velocity (Mv/sec)

Rec_grav Recalculated relative gravity (mGal)

Abs_grav Calculated absolute gravity (mGal)

VaccCor Vertical acceleration correction (mGal)

EotvosCor Eotvos correction (mGal)

LatCor Latitude correction (mGal)

FaCor Free air correction (mGal)

HaccCor Horizontal acceleration correction (mGal)

Free air Channels

FAA Un-filtered free air anomaly (mGal)

FAA_up1976 Filtered free air anomaly upward continued to a height of 1976 m...(4)

Data quality:

The following parameters have no values: St_Real, Abs_Grav, EotvosCor, LatCor, FaCor, HaccCor

Metadata

File identifier

5de1230c-33f5-4586-821b-e6c40316d6bd XML

Metadata language

English

Character set

UTF8

Hierarchy level

Dataset

Hierarchy level name

dataset

Date stamp

2019-12-04

Metadata standard name

ISO 19115 Geographic Information - Metadata

Metadata standard version

ISO 19115:2003(E)

Metadata author

Organisation name	Individual name	Electronic mail address	Role
NERC EDS UK Polar Data Centre		polardatacentre@bas.ac.uk	Point of contact