Add more metadata from Sentinel-1 Prodict Specification

xarray_sentinel/conventions.py

@@ -1,24 +1,61 @@
+"""CF representation of metadata according to
+Sentinel-1 Product Specification: S1-RS-MDA-52-7441, DI-MPC-PB, MPC-0240, 3/7, 27/02/2020 See:
+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"
+        ),
+    },
+}
+
 VARIABLE_ATTRIBUTES = {
-    "azimuth_time": {"long_name": "azimuth time", "standard_name": "time"},
+    "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"},
-    "latitude": {"units": "degrees_north"},
-    "longitude": {"units": "degrees_east"},
-    "height": {"units": "m"},
-    "incidenceAngle": {"units": "degrees"},
-    "elevationAngle": {"units": "degrees"},
-    "q0": {"units": "1"},
-    "q1": {"units": "1"},
-    "q2": {"units": "1"},
-    "q3": {"units": "1"},
-    "roll": {"units": "degrees"},
-    "pitch": {"units": "degrees"},
-    "yaw": {"units": "degrees"},
+    "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"},
     "time": {"standard_name": "time"},
     "x": {"units": "m", "long_name": "position x"},
     "y": {"units": "m", "long_name": "position y"},
@@ -29,10 +66,11 @@
 }
 
 
-def update_attributes(ds: xr.Dataset) -> xr.Dataset:
+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-1.7"
     ds.attrs["history"] = f"created by xarray_sentinel-{__version__}"
+    ds.attrs.update(GROUP_ATTRIBUTES.get(group, {}))  # type: ignore
     for var in ds.variables:
         attrs = VARIABLE_ATTRIBUTES.get(str(var), {})
         ds.variables[var].attrs.update(attrs)  # type: ignore

xarray_sentinel/sentinel1.py

@@ -47,7 +47,7 @@ def open_gcp_dataset(annotation_path: esa_safe.PathType) -> xr.Dataset:
             "slant_range_time": sorted(slant_range_time),
         },
     )
-    conventions.update_attributes(ds)
+    conventions.update_attributes(ds, group="gcp")
     return ds
 
 
@@ -66,7 +66,7 @@ def open_attitude_dataset(annotation_path: esa_safe.PathType) -> xr.Dataset:
         data_vars=data_vars,  # type: ignore
         coords={"time": [np.datetime64(dt) for dt in time]},
     )
-    ds = conventions.update_attributes(ds)
+    ds = conventions.update_attributes(ds, group="attitude")
     return ds
 
 
@@ -102,7 +102,7 @@ def open_orbit_dataset(annotation_path: esa_safe.PathType) -> xr.Dataset:
         attrs=attrs,  # type: ignore
         coords={"time": [np.datetime64(dt) for dt in time]},
     )
-    ds = conventions.update_attributes(ds)
+    ds = conventions.update_attributes(ds, group="orbit")
     return ds