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 and the Bedmap3 publication in any publication as follows:

DATA:

Fremand, A., Fretwell, P., Bodart, J., Pritchard, H., Aitken, A., Bamber, J., Bell, R. E., Bianchi, C., Bingham, R., Blankenship, D., Casassa, G., Catania, G., Christianson, K., Conway, H., Corr, H., Cui, X., Damaske, D., Damm, V., Drews, R., ... Zirizzotti, A. (2022). BEDMAP3 - Ice thickness, bed and surface elevation for Antarctica - standardised data points (Version 1.0) [Data set]. NERC EDS UK Polar Data Centre. https://doi.org/10.5285/91523FF9-D621-46B3-87F7-FFB6EFCD1847

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:

The primary source data consist of survey point measurements of ice thickness, bed elevation and surface elevation, which principally comes from airborne radar surveys and seismic soundings, and to a smaller extent from ground-based radar surveys.

All the data have been standardised to a specific CSV format. The format consists of (i) an extended header section where (a) each line is introduced by a comment ("#") character, (b) each line contains a single header item, (c) the colon character (":") is used as the key/value separator, (d) units are in parentheses, (e) attributes preferably use a common vocabulary such as the CF convention and includes attributes from the ACDD; (ii) a header row composed of the column name following the CF convention and units in parentheses; and finally (iii) the data using comma as the separator. The extended header consists of general information regarding each campaign such as the year, the name of the main investigator, funding and processing details.

The variable names are as follows:

trajectory_id Line or Flight ID

trace_number Trace number from the specific line given in Line_ID

longitude Longitude (WGS84 EPSG: 4326) in decimal degrees

latitude Latitude (WGS84 EPSG: 4326) in decimal degrees

date Date following ISO 8601 format: YYYY: year, MM: month, DD: day

time_UTC UTC time following ISO 8601 format: HH: hours, MM: minutes, SS: seconds

surface_altitude Surface elevation or altitude (referenced to WGS84) in meters

land_ice_thickness Ice thickness in meters

bedrock_altitude Bed elevation or altitude (referenced to WGS84) in meters

two_way_travel_time Two-way travel time in seconds

aircraft_altitude Aircraft elevation or altitude when applicable (referenced to WGS84) in meters

along_track_distance Distance in the along-track direction in meters

Data quality:

All non-value data were converted to -9999, including any negative ice thickness values and any points with clear outliers. We checked the minimum and maximum values of each field to ensure the data are in a reasonable range and calculated mean and standard deviation on each dataset to identify potential issues. For example, if longitude/latitude values did not fall within the expected -180 to 180 or -50 to -90 degrees range respectively, the entire row was removed. When no ice thickness values were provided but surface and bed elevation values existed, we simply calculated ice thickness by subtracting the surface value from the bed value. At times, bed elevation was higher than surface elevation, likely due to issues with the semi-automatic picker used to extract the surface and bed reflector or a lack of distinctive reflectors in areas of shallow ice. To prevent this affecting the gridded product, we converted these values to -9999 for both the surface and the bed. Finally, we also conducted routine checks on the ice thickness data by comparing the given ice thickness value with the inferred ice thickness calculated from subtracting surface with bed. If these did not match, we placed -9999 on the ice thickness values.

File naming conventions were also used throughout to easily identify a specific dataset as follows: DataProvider_Year_CampaignName_TypeofData_BM3. The type of data used was separated into three categories: Airborne Radar (AIR), Ground-based Radar (GRN), and Seismic (SEI) data. The 'BM3' abbreviation at the end identifies the datasets was part of the Bedmap3 compilation to differentiate from the Bedmap 1 and 2 (BM1 and BM2) compilations. For instance, the file named 'NASA_2019_ICEBRIDGE_AIR_BM3.csv' refers to the ICEBRIDGE airborne campaign led by NASA in 2019.