This data set is part of the ESA Greenland Ice sheet CCI project. The data set provides surface elevation changes (SEC) for the Greenland Ice sheet derived from satellite (ERS‐1, ERS‐2, Envisat and Cryosat) radar altimetry. The ice mask is based on the GEUS/GST land/ice/ocean mask provided as part of national mapping projects, and based on 1980’s aerial photography. The data from ERS and Envisat are based on a 5‐year running average, using combined algorithms of repeat‐track (RT), along‐track (AT) or cross‐over (XO) algorithms, and include propagated error estimates.
It is important to note that different processing algorithms were applied to the ERS‐1, ERS‐2, Envisat and CryoSat data; for details see the Product User Guide (PUG), available on the CCI website and in the documentation section here. For ERS‐1, the radar data were processed using a cross‐over algorithm (XO) only. For ERS‐2 data and Envisat data in repeat mode, a combination of RT and XO algorithms was applied, followed by filtering. For across‐mission (i.e. ERS‐2‐Envisat) combinations, and for Envisat operating in a drifting orbit, an AT and XO combination was applied (the difference between RT and AT algorithms is that AT use reference tracks and searches for data in the vicinity of this track). For CryoSat data a binning/gridding and plane fit method has been applied, following by weak filtering (0.05 degree resolution).
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Public data: access to these data is available to both registered and non-registered users.
Use of these data is covered by the following licence: http://licences.ceda.ac.uk/image/data_access_condition/esacci_icesheets_greenland_terms_and_conditions.pdf. When using these data you must cite them correctly using the citation given on the CEDA Data Catalogue record.
Data were processed by the ESA CCI Greenland Ice Sheet project team and supplied to CEDA in the context of the ESA CCI Open Data Portal Project.
Files are provided in both NetCDF (.nc) and ASCII Gravsoft (.gri) format, as well as .png images. In ascii gravsoft format the data are stored row‐wise in E‐W rows, from N to S, headed by a two‐line label defining coordinate limits and projection. This format is the simplest possible ASCII grid format. Unknown values are flagged by 9999. The grid label for the CCI data is: ‐3350000. ‐650000. ‐650000. 850000. 5000. 5000. (this is N1, N2, E1, E2, dN, DE in meter) ‐70 ‐45 (minus reference latitude, central meridian in degrees) The CCI data grid contains a total 541 x 301 points. First data value in file is thus the NW cormer (N = ‐650 km,E = ‐650 km) and last value the SE corner (N = ‐3350 km, E = 850 km). Stereographic projections have by default (0,0) at the North Pole. The data use a Polar stereographic projection, WGS84 ellipsoid, with a reference latitude of 70N, and central meridian of 45W
- units: meters
- long_name: Cartesian x-coordinate - easting
- standard_name: projection_x_coordinate
- var_id: x
- names: projection_x_coordinate, Cartesian x-coordinate - easting
- units: meters
- long_name: Cartesian y-coordinate - northing
- standard_name: projection_y_coordinate
- var_id: y
- names: projection_y_coordinate, Cartesian y-coordinate - northing
- long_name: Error estimates associated with surface elevation changes
- var_id: SEC_error
- names: Error estimates associated with surface elevation changes
- var_id: landtype
- long_name: Land type definition.
- names: Land type definition.
- var_id: lat
- long_name: Latitude
- units: degrees north
- names: Latitude
- long_name: Number of observations in the grid used
- var_id: Grid_observations
- names: Number of observations in the grid used
- long_name: Surface elevation changes, filtered
- var_id: SEC
- names: Surface elevation changes, filtered
- var_id: grid_projection
- var_id: lon
- units: degrees east
- long_name: longitude
- names: longitude