These laser altimetry data were collected as part of the 2023-24
NSF COLDEX CXA2 airborne campaign targeting the southern flank of East Antarctica's Dome A. In this Level 2 product, we have used the laser range to the surface and complementary aircraft position data to calculated the ice surface elevation, which is an important constraint on ice flow. Complementary radar, gravity, magnetics and imagery were also collected.
Data format:Data are formatted as text files with a header and the following tab delimited format columns. Data are in the same format as similar IceBridge ILUTP2 altimetry data.
Field 1: Year (UTC)
Field 2: Day of year (UTC)
Field 3: Second of day (UTC)
Field 4: Longitude Angle (deg) (WGS-84)
Field 5: Latitude Angle (deg) (WGS-84)
Field 6: Laser Derived Surface Elevation (m) (WGS-84)
Missing values have been replaced by "nan". The effective footprint of the laser data is 25 m along track by 1 meter across track. Some cloud filtering was performed.
Uncertainties: A comparison of this laser altimetry dataset north of 87.5˚S with the REMAv2 100 m mosaic digital terrain model indicate a median bias of 17 cm and a root mean squared (RMS) difference of 20 cm. Intersections between profiles within this survey, on the Antarctic Plateau but away from South Pole Station, have RMS differences of 6.8 cm.
Datum: WGS-84 ellipsoid; ITRF 2008
Geolocation: Positioning and orientation for CXA1 came from loosely coupled joint PPP/inertial solutions using a Novatel OEM-4 GPS receiver and an iMAR FSAS IMU.
Pointing bias: roll: 0.340 degrees; pitch: -0.505 degrees
Pointing angle (pointing bias) is the angular offset of the downward-pointing laser boresight respect to the vehicle body frame's vertical (Z) axis. This estimated angle is derived by comparing measurements at crossovers. Pointing angle is provided in the vehicle body frame, using the laser origin for the rotation node. A positive pitch rotation indicates that the laser beam intersects the ground forward of the z-axis. A positive roll rotation indicates that the laser beam intersects the ground left of the z-axis. Pointing biases were found using the minimization of cross over difference method from Young et al., 2015.
Level arm: X: 0 m; Y: 0.2 m; Z: -0.22 m
The lever arm is the position of the laser origin relative to the aircraft position solution, estimated using crossover-error minimization. Lever arm is provided in the vehicle body frame, with +X is forward, +Y is right, and +Z is down. Lever arm was measured after installation in the field.
GNSS_antenna: AeroAntenna AT1675-17W-TCNF-000-RG-36-NM
The coordinate system for the laser-gps lever arm is X forward, Y right, and Z down, from the center of position.
