From c6ea2c1438eb33d5446464c8090240be21e16749 Mon Sep 17 00:00:00 2001
From: Sam Cranford <scranford@creare.com>
Date: Thu, 24 Sep 2026 16:12:33 +0000
Subject: [PATCH] FIX: Check CRS equality relying on string comparison

---
 podpac/core/coordinates/coordinates.py        | 26 ++++++++++++--
 .../core/coordinates/test/test_coordinates.py | 36 ++++++++++++++++++-
 2 files changed, 59 insertions(+), 3 deletions(-)

diff --git a/podpac/core/coordinates/coordinates.py b/podpac/core/coordinates/coordinates.py
index 6229ccf9..3abdc1a0 100644
--- a/podpac/core/coordinates/coordinates.py
+++ b/podpac/core/coordinates/coordinates.py
@@ -1691,7 +1691,7 @@ def merge_dims(coords_list, validate_crs=True):
 
     # check crs
     crs = coords_list[0].crs
-    if validate_crs and not all(coords.crs == crs for coords in coords_list):
+    if validate_crs and not all(_crs_equal(coords.crs, crs) for coords in coords_list):
         raise ValueError("Cannot merge Coordinates, crs mismatch")
 
     # merge
@@ -1728,7 +1728,7 @@ def concat(coords_list):
 
     # check crs
     crs = coords_list[0].crs
-    if not all(coords.crs == crs for coords in coords_list):
+    if not all(_crs_equal(coords.crs, crs) for coords in coords_list):
         raise ValueError("Cannot concat Coordinates, crs mismatch")
 
     # concatenate
@@ -1769,3 +1769,25 @@ def union(coords_list):
     """
 
     return concat(coords_list).unique()
+
+
+def _crs_equal(a: str | None, b: str | None) -> bool:
+    """Check if two CRS strings define the same coordinate reference system.
+
+    Parameters
+    ----------
+    a : str | None
+        The first CRS string or None.
+    b : str | None
+        The second CRS string or None.
+
+    Returns
+    -------
+    bool
+        True if the strings define the same CRS, otherwise False.
+    """
+    if a == b:
+        return True
+    if a is None or b is None:
+        return False
+    return pyproj.CRS(a) == pyproj.CRS(b)
diff --git a/podpac/core/coordinates/test/test_coordinates.py b/podpac/core/coordinates/test/test_coordinates.py
index 996e15dd..94c71520 100644
--- a/podpac/core/coordinates/test/test_coordinates.py
+++ b/podpac/core/coordinates/test/test_coordinates.py
@@ -16,7 +16,7 @@
 from podpac.core.coordinates.uniform_coordinates1d import UniformCoordinates1d
 from podpac.core.coordinates.cfunctions import crange, clinspace
 from podpac.core.coordinates.coordinates import Coordinates
-from podpac.core.coordinates.coordinates import concat, union, merge_dims
+from podpac.core.coordinates.coordinates import concat, union, merge_dims, _crs_equal
 
 _DIMENSION_MISMATCH = "Dimension mismatch"
 _MERCATOR_CRS = "+proj=merc +lat_ts=56.5 +ellps=GRS80"
@@ -1822,6 +1822,40 @@ def test_concat_crs(self):
         with pytest.raises(ValueError, match="Cannot concat Coordinates"):
             concat([c1, c2])
 
+    def test_crs_equal(self):
+        """Test CRS equality for WKT strings and shorthand codes."""
+        wkt = pyproj.CRS("EPSG:4326").to_wkt()
+        assert _crs_equal("EPSG:4326", "EPSG:4326")
+        assert _crs_equal("EPSG:4326", wkt)
+        assert _crs_equal(None, None)
+        assert not _crs_equal("EPSG:4326", None)
+        assert not _crs_equal(None, "EPSG:4326")
+        assert not _crs_equal("EPSG:4326", "EPSG:2193")
+
+    def test_merge_dims_equivalent_crs(self):
+        """Test coordinate merging with equivalent WKT strings and shorthand codes."""
+        wkt = pyproj.CRS("EPSG:4326").to_wkt()
+        clat = Coordinates([[2, 4, 5]], dims=["lat"], crs=wkt)
+        clon = Coordinates([[3, -1, 5]], dims=["lon"], crs="EPSG:4326")
+
+        c = merge_dims([clat, clon])
+        assert c.dims == ("lat", "lon")
+        assert c.crs == wkt
+
+    def test_concat_and_union_equivalent_crs(self):
+        """Test concatenation and union with equivalent WKT strings and shorthand codes."""
+        wkt = pyproj.CRS("EPSG:4326").to_wkt()
+        c1 = Coordinates([[0, 1]], dims=["lat"], crs=wkt)
+        c2 = Coordinates([[1, 2]], dims=["lat"], crs="EPSG:4326")
+
+        c = concat([c1, c2])
+        assert c.shape == (4,)
+        assert c.crs == wkt
+
+        c = union([c1, c2])
+        assert c.shape == (3,)
+        assert c.crs == wkt
+
 
 class TestCoordinatesGeoTransform(object):
     def test_uniform_working(self):