sp3: make t0 scalar dataset rather than attribute for netcdf4 write

fixes #95

Co-authored-by: linustan <[email protected]>

.github/workflows/ci.yml

@@ -27,7 +27,7 @@ jobs:
           experimental: false
 
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - uses: actions/setup-python@v4
       with:
         python-version: ${{ matrix.python-version }}

src/georinex/sp3.py

@@ -24,12 +24,14 @@ def load_sp3(fn: Path, outfn: Path) -> xarray.Dataset:
 
     http://epncb.oma.be/ftp/data/format/sp3_docu.txt  (sp3a)
     """
+
     dat: dict[T.Hashable, T.Any] = {}
+
     with opener(fn) as f:
         ln = first_nonblank_line(f)
         assert ln[0] == "#", f"failed to read {fn} line 1"
         # sp3_version = ln[1]
-        dat["t0"] = sp3dt(ln)
+        t0 = sp3dt(ln)
         # Nepoch != number of time steps, at least for some files
         dat["Nepoch"] = int(ln[32:39])
         dat["coord_sys"] = ln[46:51]
@@ -105,6 +107,7 @@ def load_sp3(fn: Path, outfn: Path) -> xarray.Dataset:
     ecefs.append(ecef)
     clocks.append(clock)
     vels.append(vel)
+
     aclock = np.asarray(clocks)
 
     # assemble into final xarray.Dataset
@@ -115,6 +118,8 @@ def load_sp3(fn: Path, outfn: Path) -> xarray.Dataset:
     ds["velocity"] = (("time", "sv", "ECEF"), vels)
     ds["dclock"] = (("time", "sv"), aclock[:, :, 1])
 
+    ds["t0"] = t0
+
     ds.attrs = dat
 
     if outfn:

src/georinex/tests/test_conv.py

@@ -71,6 +71,22 @@ def test_netcdf_write(tmp_path):
     assert obs.equals(wobs)
 
 
+def test_netcdf_write_sp3(tmp_path):
+    """
+    NetCDF4 wants suffix .nc -- arbitrary tempfile.NamedTemporaryFile names do NOT work!
+    """
+    pytest.importorskip("netCDF4")
+
+    fn = tmp_path / "sp3.nc"
+    obs = gr.load(R / "example1.sp3a", out=fn)
+
+    wobs = xarray.load_dataset(fn)
+
+    assert obs.equals(wobs)
+
+    assert obs.attrs == wobs.attrs
+
+
 def test_locs():
     pytest.importorskip("pymap3d")  # need to have this
     gg = pytest.importorskip("georinex.geo")