Error with waitForTransform (triggers can_transform) tf2

asked 2020-09-27 12:23:12 -0500

moshahin gravatar image

updated 2020-09-27 12:24:49 -0500

I am writing some python code to read coordinates from a textfile and transform the coordinates to a PointStamped in my odom frame, sending the goal to move_base for navigation. When the first set of coordinates are read, everything is fine however when it comes to the next set of coordinates I get this error:

Traceback (most recent call last):
  File "/home/moshahin/catkin_ws/src/monsterborg_navigation/src/", line 184, in <module>
    odom_point = PointTransformation(UTM_point)
  File "/home/moshahin/catkin_ws/src/monsterborg_navigation/src/", line 89, in PointTransformation
    listener.waitForTransform('odom', 'utm',, rospy.Duration(10.0))
  File "/opt/ros/melodic/lib/python2.7/dist-packages/tf/", line 74, in waitForTransform
    can_transform, error_msg = self._buffer.can_transform(strip_leading_slash(target_frame), strip_leading_slash(source_frame), time, timeout, return_debug_tuple=True)
  File "/opt/ros/melodic/lib/python2.7/dist-packages/tf2_ros/", line 124, in can_transform
  File "/opt/ros/melodic/lib/python2.7/dist-packages/rospy/", line 103, in sleep
  File "/opt/ros/melodic/lib/python2.7/dist-packages/rospy/", line 165, in sleep
    raise rospy.exceptions.ROSInterruptException("ROS shutdown request")
rospy.exceptions.ROSInterruptException: ROS shutdown request

The function PointTransformation has the following body:

def PointTransformation(UTMPoint_input):
    """ The purpose of this function is to transform the POI from the UTM frame
        to the odom frame (this can later be changed to transform to map frame instead).
        The input of this function is a geometry_msg/PointStamped w.r.t UTM frame.
        The OUTPUT of this function is a geometry_msg/PointStamped w.r.t odom/map frame. """

    TransformedPoint = PointStamped()
    listener = tf.TransformListener()
    notDone = True

    while notDone:
            UTMPoint_input.header.stamp =
            listener.waitForTransform('odom', 'utm',, rospy.Duration(10.0))

            # Transforms geometry_msgs/PointStamped message to frame target_frame=odom
            TransformedPoint = listener.transformPoint('odom', UTMPoint_input)
            notDone = False
        except tf.Exception:
            rospy.logerr("tf.Exception occured! ")

    return TransformedPoint

I have setup the robot_localization package such that the utm frame is the parent frame and its child is odom frame. The function takes in a PointStamped message w.r.t utm frame and this function transforms it to a PointStamped w.r.t to odom frame. Just to re-iterate, the first time the function is called, nothing is wrong (and I get the point w.r.t odom which I then use to build a move_base_goal)but I get the error I posted above when the function is executed for the second set of GPS coordinates. So my question is why do I get this error? What is the can_transform function?

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