fix: adapt CRS depending on domain

src/icefabric/hydrofabric/subset_nhf.py

@@ -158,7 +158,12 @@ def load_columns(self, layer: str, columns: list[str]) -> pl.DataFrame:
 
 
 def pl_to_gdf(pl_df: pl.DataFrame, crs: str = "EPSG:5070") -> gpd.GeoDataFrame:
-    """Convert Polars DataFrame with WKB geometry to GeoDataFrame."""
+    """Convert Polars DataFrame with WKB geometry to GeoDataFrame.
+
+    NHF geometries are ingested into Iceberg as WKB without reprojection, so
+    the caller is responsible for supplying the native CRS of the source
+    domain (see ``HydrofabricNamespace.crs``).
+    """
     df = pl_df.to_pandas()
     df["geometry"] = gpd.GeoSeries.from_wkb(df["geometry"])
     return gpd.GeoDataFrame(df, crs=crs)
@@ -205,6 +210,7 @@ def generate_subset_from_ids(
 ) -> dict[str, gpd.GeoDataFrame]:
     """Subset hydrofabric to a given set of flowpath IDs."""
     logger.debug(f"Subsetting {len(flowpath_ids)} flowpaths")
+    crs = source.namespace.crs
 
     # Wave 1: fp_id/div_id filtered (parallel)
     with ThreadPoolExecutor(max_workers=6) as ex:
@@ -277,14 +283,14 @@ def generate_subset_from_ids(
     # Write output
     # ======================================================================
     output = {
-        "flowpaths": pl_to_gdf(subset_fp),
-        "nexus": pl_to_gdf(subset_nex),
-        "divides": pl_to_gdf(subset_div),
-        "virtual_nexus": pl_to_gdf(subset_v_nex),
-        "virtual_flowpaths": pl_to_gdf(subset_v_fp),
-        "waterbodies": pl_to_gdf(subset_wb) if len(subset_wb) > 0 else subset_wb.to_pandas(),
-        "gages": pl_to_gdf(subset_gages) if len(subset_gages) > 0 else subset_gages.to_pandas(),
-        "lakes": pl_to_gdf(subset_lakes) if len(subset_lakes) > 0 else subset_lakes.to_pandas(),
+        "flowpaths": pl_to_gdf(subset_fp, crs=crs),
+        "nexus": pl_to_gdf(subset_nex, crs=crs),
+        "divides": pl_to_gdf(subset_div, crs=crs),
+        "virtual_nexus": pl_to_gdf(subset_v_nex, crs=crs),
+        "virtual_flowpaths": pl_to_gdf(subset_v_fp, crs=crs),
+        "waterbodies": pl_to_gdf(subset_wb, crs=crs) if len(subset_wb) > 0 else subset_wb.to_pandas(),
+        "gages": pl_to_gdf(subset_gages, crs=crs) if len(subset_gages) > 0 else subset_gages.to_pandas(),
+        "lakes": pl_to_gdf(subset_lakes, crs=crs) if len(subset_lakes) > 0 else subset_lakes.to_pandas(),
         "reference_flowpaths": subset_ref_fp.to_pandas(),
         "hydrolocations": subset_hydrolocations.to_pandas(),
     }

src/icefabric/schemas/hydrofabric.py

@@ -184,6 +184,20 @@ def is_oconus_hf(self) -> bool:
             HydrofabricNamespace.GREAT_LAKES_HF,
         )
 
+    @property
+    def crs(self) -> str:
+        """Return the EPSG CRS string for this namespace's native geometries.
+
+        NHF geometries are ingested without reprojection, so the CRS differs by
+        domain and must be re-applied when reading WKB back out of Iceberg.
+        """
+        oconus_nhf_crs = {
+            HydrofabricNamespace.ALASKA_NHF: "EPSG:3338",
+            HydrofabricNamespace.HAWAII_NHF: "EPSG:32604",
+            HydrofabricNamespace.PUERTO_RICO_NHF: "EPSG:6566",
+        }
+        return oconus_nhf_crs.get(self, "EPSG:5070")
+
     @classmethod
     def _missing_(cls, value: object) -> HydrofabricNamespace | None:
         """Handle legacy string values."""

tests/app/test_source_parameter.py

@@ -229,6 +229,23 @@ def test_is_oconus_hf_for_hawaii(self):
         """Test is_oconus_hf returns False for HAWAII_HF namespace (it's OCONUS but not in the set)."""
         assert HydrofabricNamespace.HAWAII_HF.is_oconus_hf is False
 
+    def test_crs_for_conus_nhf(self):
+        """CONUS NHF is stored in EPSG:5070 (NAD83 / Conus Albers)."""
+        assert HydrofabricNamespace.NHF.crs == "EPSG:5070"
+        assert HydrofabricNamespace.CONUS_NHF.crs == "EPSG:5070"
+
+    def test_crs_for_alaska_nhf(self):
+        """Alaska NHF is stored in EPSG:3338 (NAD83 / Alaska Albers)."""
+        assert HydrofabricNamespace.ALASKA_NHF.crs == "EPSG:3338"
+
+    def test_crs_for_hawaii_nhf(self):
+        """Hawaii NHF is stored in EPSG:32604 (WGS 84 / UTM 4N)."""
+        assert HydrofabricNamespace.HAWAII_NHF.crs == "EPSG:32604"
+
+    def test_crs_for_puerto_rico_nhf(self):
+        """Puerto Rico / USVI NHF is stored in EPSG:6566."""
+        assert HydrofabricNamespace.PUERTO_RICO_NHF.crs == "EPSG:6566"
+
 
 class TestHydrofabricRouterSourceParameter:
     """Integration tests for the hydrofabric router source parameter."""