BUG: Fix transformer list for 3D transformations in TransformerGroup (#1075)

Author: snowman2

docs/history.rst

@@ -4,6 +4,7 @@ Change Log
 Latest
 -------
 - DEP: Minimum PROJ version 8.1 (issue #1011)
+- BUG: Fix transformer list for 3D transformations in :class:`pyproj.transformer.TransformerGroup` (discussion #1072)
 
 3.3.1
 -------

pyproj/_transformer.pyx

@@ -172,8 +172,8 @@ cdef class _TransformerGroup:
             )
             pj_operations = proj_create_operations(
                 self.context,
-                get_transform_crs(crs_from).projobj,
-                get_transform_crs(crs_to).projobj,
+                crs_from.projobj,
+                crs_to.projobj,
                 operation_factory_context,
             )
             num_operations = proj_list_get_count(pj_operations)
@@ -216,16 +216,6 @@ cdef class _TransformerGroup:
             ProjError.clear()
 
 
-cdef _CRS get_transform_crs(_CRS in_crs):
-    for sub_crs in in_crs.sub_crs_list:
-        if (
-            not sub_crs.type_name.startswith("Temporal") and
-            not sub_crs.type_name.startswith("Temporal")
-        ):
-            return sub_crs.source_crs if sub_crs.is_bound else sub_crs
-    return in_crs.source_crs if in_crs.is_bound else in_crs
-
-
 cdef PJ* proj_create_crs_to_crs(
     PJ_CONTEXT *ctx,
     const char *source_crs_str,

test/test_transformer.py

@@ -709,7 +709,7 @@ def test_transformer_group__get_transform_crs():
     if not grids_available("nl_nsgi_rdtrans2018.tif"):
         assert len(tg.transformers) == 1
     else:
-        assert len(tg.transformers) == 2
+        assert len(tg.transformers) == 6
 
 
 @pytest.mark.grid