diff --git a/src/weather_model_graphs/create/base.py b/src/weather_model_graphs/create/base.py
index fbfa93b..792184b 100644
--- a/src/weather_model_graphs/create/base.py
+++ b/src/weather_model_graphs/create/base.py
@@ -157,9 +157,21 @@ def create_all_graph_components(
         G_target=grid_connect_graph,
         method=g2m_connectivity,
         **g2m_connectivity_kwargs,
-    )
+)
     graph_components["g2m"] = G_g2m
 
+    grid_nodes_in_g2m = {u for u, v in G_g2m.edges()}
+    all_grid_nodes = set(G_grid.nodes)
+    missing_nodes = all_grid_nodes - grid_nodes_in_g2m
+
+    if missing_nodes:
+        raise ValueError(
+            f"Found {len(missing_nodes)} grid node(s) with no g2m connection! "
+            f"Missing nodes: {missing_nodes}. "
+            f"This means these grid nodes won't participate in the encode phase. "
+            f"Try increasing g2m rel_max_dist or max_dist."
+        )
+
     if decode_mask is None:
         # decode to all grid nodes
         decode_grid = G_grid
@@ -407,6 +419,7 @@ def _find_neighbour_node_idxs_in_source_mesh(xy_target):
     for target_node in target_nodes_list:
         xy_target = G_target.nodes[target_node]["pos"]
         neigh_idxs = _find_neighbour_node_idxs_in_source_mesh(xy_target)
+        neigh_idxs = np.atleast_1d(neigh_idxs)
         for i in neigh_idxs:
             source_node = source_nodes_list[i]
             # add edge from source to target
diff --git a/src/weather_model_graphs/create/mesh/kinds/flat.py b/src/weather_model_graphs/create/mesh/kinds/flat.py
index 92f47b0..a371a4c 100644
--- a/src/weather_model_graphs/create/mesh/kinds/flat.py
+++ b/src/weather_model_graphs/create/mesh/kinds/flat.py
@@ -6,7 +6,7 @@
 
 
 def create_flat_multiscale_mesh_graph(
-    xy, mesh_node_distance: float, level_refinement_factor: int, max_num_levels: int
+    xy, mesh_node_distance: float, level_refinement_factor: int, max_num_levels: int,
 ):
     """
     Create flat mesh graph by merging the single-level mesh
diff --git a/tests/test_spherical_coords.py b/tests/test_spherical_coords.py
new file mode 100644
index 0000000..baaf273
--- /dev/null
+++ b/tests/test_spherical_coords.py
@@ -0,0 +1,47 @@
+import numpy as np
+import pytest
+import weather_model_graphs as wmg
+from weather_model_graphs.create.base import create_all_graph_components
+
+def test_flat_coords():
+    coords=np.array([[0,0],[0,1],[1,0],[1,1]])
+    graph=wmg.create.archetype.create_keisler_graph(
+        coords=coords,
+        mesh_node_distance=0.5
+    )
+    assert len(graph.nodes) > 0
+    assert len(graph.edges) > 0
+    print(f"Success flat graph has {len(graph.nodes)}nodes and {len(graph.edges)}edges")
+
+
+def test_spherical_coords():
+    coords=np.array([
+        [-10.0,0.0],
+        [10.0,0.0],
+        [0.0,10.0],
+        [0.0,-10.0],
+    ])
+    graph=wmg.create.archetype.create_keisler_graph(
+        coords=coords,
+        coords_crs="EPSG:4326",
+        graph_crs="EPSG:3857",
+        mesh_node_distance=500_000
+    )
+    assert len(graph.nodes) > 0
+    assert len(graph.edges) > 0
+    for _, _, data in graph.edges(data=True):
+        if 'len' in data:
+            print(f"Edge length in metres:{data['len']:.1f}m")
+    print(f"Success! Spherical graph has {len(graph.nodes)} nodes and {len(graph.edges)} edges")
+
+
+
+if __name__ == "__main__":
+    print("Running Test 1 --Flat Cartesian...")
+    test_flat_coords()
+
+    print("\nRunning Test 2 --Spherical....")
+    test_spherical_coords()
+
+    print("\nAll Tests Passed!")
+