fix: support context dict key for humble (autowarefoundation#328)

* fix: support context dict key for humble

Signed-off-by: wep21 <border_goldenmarket@yahoo.co.jp>

* add todo comment

Co-authored-by: Kenji Miyake <31987104+kenji-miyake@users.noreply.github.com>

Co-authored-by: Kenji Miyake <31987104+kenji-miyake@users.noreply.github.com>

perception_launch/launch/obstacle_segmentation/ground_segmentation/ground_segmentation.launch.py

@@ -48,8 +48,11 @@ def __init__(self, context):
         self.use_time_series_filter = self.ground_segmentation_param["use_time_series_filter"]
 
     def get_vehicle_info(self):
-        # TODO: need to rename key from "ros_params" to "global_params" after Humble
+        # TODO(TIER IV): Use Parameter Substitution after we drop Galactic support
+        # https://github.com/ros2/launch_ros/blob/master/launch_ros/launch_ros/substitutions/parameter.py
         gp = self.context.launch_configurations.get("ros_params", {})
+        if not gp:
+            gp = self.context.launch_configurations.get("global_params", {})
         p = {}
         p["vehicle_length"] = gp["front_overhang"] + gp["wheel_base"] + gp["rear_overhang"]
         p["vehicle_width"] = gp["wheel_tread"] + gp["left_overhang"] + gp["right_overhang"]