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:

Ferraccioli, F., Jones, P., Curtis, M., Leat, P., & Riley, T. (2020). Processed line aerogravity data over the Jutulstraumen rift area (2001/02 season) [Data set]. UK Polar Data Centre, Natural Environment Research Council, UK Research & Innovation. https://doi.org/10.5285/BC870F9E-4200-4AE2-8DB0-6CB80B870C09

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.

Methodology:

Airborne gravity are presented in (Ferraccioli et al., 2005). The dataset available here includes all raw data and final free air gravity anomalies. Intermediate processing steps are not available for this dataset, but have been applied. All data is provided in the "by flight" database.

Raw data from L&R meter #S83 includes:

Channel names in brackets

Spring tension (ST) meter units

Cross coupling (CC) meter units

Raw beam position (RB) mV

Cross axis accelerometer output (XACC) mV

Long Axis accelerometer output (LACC) mV

Gravity processing steps were as follows:

1/ Calculate observed gravity (Note these channel descriptions are for reference - intermediate processing values are not available).

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 40 mGal per second.

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

Relative gravity (rec_grav) = ((ST_real+CC)*0.9966)+(Beam_velocity*k_fac), k_fac=60/2.04, meter scale value =0.9966.

Still readings are in mGal (Still), are based on readings before and after each flight.

Tie absolute gravity values for the survey (Base) were derived from land gravity measurements adjacent to the survey aircraft.

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

2/ Corrections to derive free air anomalies (disturbances) (Note these channel descriptions are for reference - intermediate processing values are not available).

Vertical acceleration (VaccCor) is calculated as 2nd derivative of flight altitude (Height_WGS1984)

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 (FAA) = the filtered free air gravity anomaly (mGal)

faa_150 = Gridded Tie line data sampled back into database used for levelling.

Lev_cor = levelling correction (mGal).

FAA_lev = levelled free air gravity anomalies.

FAA_up2964m = upward continued free air anomalies.

Note no levelling has been applied to the free air gravity data.

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

Free_air Un-filtered free air anomaly (mGal)

FAA_Lev Levelled free air anomaly data...(6)

Data quality:

The following parameters have no values: ST_Real, Beam_vel, RecGravity, Abs_grav, EotvosCor, LatCor, FaCor, HaccCor.