refactor: use kilometers per mile from const

Author: danielolsen

prereise/gather/griddata/hifld/data_process/transmission.py

@@ -18,6 +18,7 @@
     add_interconnects_by_connected_components,
     get_mst_edges,
 )
+from prereise.gather.griddata.transmission import const as transmission_const
 from prereise.gather.griddata.transmission.geometry import (
     Conductor,
     ConductorBundle,
@@ -910,7 +911,10 @@ def build_transmission(method="line2sub", **kwargs):
     first_new_id = ac_lines.index.max() + 1
     transformers.index = pd.RangeIndex(first_new_id, first_new_id + len(transformers))
     ac_lines["type"] = "Line"
-    ac_lines["length"] = ac_lines.apply(calculate_branch_mileage, axis=1) * 1.6093  # km
+    ac_lines["length"] = (
+        ac_lines.apply(calculate_branch_mileage, axis=1)
+        * transmission_const.kilometers_per_mile
+    )
     branch = pd.concat([ac_lines, transformers])
     add_impedance_and_rating(branch, bus["baseKV"], const.line_design_assumptions)