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"""CF representation of metadata according to Sentinel-1 Product Specification.
See: S1-RS-MDA-52-7441, DI-MPC-PB, MPC-0240, 3/7, 27/02/2020
https://sentinel.esa.int/documents/247904/1877131/Sentinel-1-Product-Specification
"""
import xarray as xr
from . import __version__
GROUP_ATTRIBUTES = {
"orbit": {
"title": "Orbit information used by the IPF during processing",
"comment": (
"The dataset contains a sets of orbit state vectors that are updated along azimuth."
" The values represent the interpolated values used by the IPF"
" and are derived from the sub-commutated ancillary data from the ISPs"
" or from an input auxiliary orbit file"
),
},
"attitude": {
"title": "Attitude information used by the IPF during processing",
"comment": (
"The dataset contains a sets of attitude data records that are updated along azimuth."
" The values represent the interpolated values used by the IPF"
" and are derived from the sub-commutated ancillary data from the ISPs"
" or from an input auxiliary orbit file"
),
},
"gcp": {
"title": "Geolocation grid",
"comment": (
"The dataset contains geolocation grid point entries for each line/pixel"
" combination based on a configured resolution."
" The list contains an entry for each update made along azimuth"
),
},
"calibration": {
"title": "Calibration coefficients",
"comment": (
"The dataset contains calibration information and the beta nought, sigma nought,"
" gamma and digital number (DN) Look-up Tables (LUT) that can be used for"
" absolute product calibration"
),
},
}
VARIABLE_ATTRIBUTES = {
"line": {"units": "1", "long_name": "product line number"},
"pixel": {"units": "1", "long_name": "product pixel number"},
"azimuth_time": {"long_name": "zero-Doppler azimuth time", "standard_name": "time"},
# NOTE: `slant_range_time` is not expressed as `np.timedelta64[ns]` in order to keep enough
# accuracy for interferometric processing, i.e. c * 1ns / 2 ~= 15cm.
"slant_range_time": {"units": "s", "long_name": "slant range time / two-way delay"},
"ground_range": {"units": "m", "long_name": "ground range"},
"axis": {"units": "1", "long_name": "coordinate index"},
"degree": {"units": "1", "long_name": "polynomial degree"},
"latitude": {"units": "degrees_north", "long_name": "geodetic latitude"},
"longitude": {"units": "degrees_east", "long_name": "geodetic longitude"},
"height": {"units": "m", "long_name": "height above sea level"},
"incidenceAngle": {"units": "°", "long_name": "incidence angle"},
"elevationAngle": {"units": "°", "long_name": "elevation angle"},
"q0": {"units": "1", "long_name": "Q0 attitude quaternion"},
"q1": {"units": "1", "long_name": "Q1 attitude quaternion"},
"q2": {"units": "1", "long_name": "Q2 attitude quaternion"},
"q3": {"units": "1", "long_name": "Q3 attitude quaternion"},
"roll": {"units": "°", "long_name": "platform roll"},
"pitch": {"units": "°", "long_name": "platform pitch"},
"yaw": {"units": "°", "long_name": "platform yaw"},
"wx": {"units": "° s-1", "long_name": "X component of angular velocity vector"},
"wy": {"units": "° s-1", "long_name": "Y component of angular velocity vector"},
"wz": {"units": "° s-1", "long_name": "Z component of angular velocity vector"},
"position": {"units": "m", "long_name": "ECEF position"},
"velocity": {"units": "m s-1", "long_name": "ECEF velocity"},
"sigmaNought": {"units": "m m-1", "long_name": "sigma nought calibration LUT"},
"betaNought": {"units": "m m-1", "long_name": "beta nought calibration LUT"},
"gamma": {"units": "m m-1", "long_name": "gamma calibration LUT"},
"dn": {"units": "1", "long_name": "original digital number calibration LUT"},
"noiseRangeLut": {"units": "1", "long_name": "range thermal noise correction LUT"},
"noiseAzimuthLut": {
"units": "1",
"long_name": "azimuth thermal noise correction LUT",
},
"gr0": {
"units": "m",
"long_name": "ground range origin for slant range calculation",
},
"grsrCoefficients": {
"units": "1",
"long_name": "polynomial to convert from ground range to slant range",
},
"sr0": {
"units": "m",
"long_name": "slant range origin for ground range calculation",
},
"srgrCoefficients": {
"units": "1",
"long_name": "polynomial to convert from slant range to ground range",
},
"t0": {
"units": "s",
"long_name": "Two-way slant range time origin",
},
"data_dc_polynomial": {
"units": "1",
"long_name": "Coppler centroid estimated from data",
},
"azimuth_fm_rate_polynomial": {
"units": "1",
"long_name": "Azimuth FM rate coefficient array",
},
"measurement": {"units": "1", "long_name": "digital number"},
}
def update_attributes(ds: xr.Dataset, group: str = "") -> xr.Dataset:
# NOTE: keep the version in sync with the capabilities of CF compliance checkers
ds.attrs["Conventions"] = "CF-1.8"
ds.attrs.update(GROUP_ATTRIBUTES.get(group, {}))
ds.attrs["history"] = f"created by xarray_sentinel-{__version__}"
for var in ds.variables:
attrs = VARIABLE_ATTRIBUTES.get(str(var), {})
ds.variables[var].attrs.update(attrs)
return ds
|
