[ros-users] Trouble converting points with TF

[Daniel Chavez]

I'm having some trouble getting TF to convert a point from /base_link frame
to /map frame.  I made a function for it, shown below, based on code in the
TF tutorials:

geometry_msgs::PointStamped baseToMapFrame(geometry_msgs::PointStamped p)
{
        tf::TransformListener TFlistener(ros::Duration(1.0));  //Used for
listening to transforms
        geometry_msgs::PointStamped q;
        try{  
                ros::Time now = ros::Time::now();
                geometry_msgs::PointStamped p,q;
                p.header.frame_id = "/base_link";
                p.header.stamp = ros::Time(0);
                TFlistener.transformPoint("/map",p,q);
        } catch (tf::TransformException ex){
            ROS_ERROR("%s",ex.what());
       }
        return q;
}

The error message I get when running is:

[ERROR] [1287786203.075208516, 13.800000000]: Frame id /map does not exist!
When trying to transform between /base_link and /map.

This is even after initializing the map frame with AMCL.  Strangely, if I do
tf_echo to see if TF knows this conversion, I get:

$ rosrun tf tf_echo /map /base_link
Failure at 75.200000000
Exception thrown:Frame id /map does not exist! When trying to transform
between /base_link and /map.
The current list of frames is:

At time 76.100
- Translation: [46.885, 45.869, 0.000]
- Rotation: in Quaternion [0.000, 0.000, 1.000, -0.022]
            in RPY [0.000, -0.000, -3.097]
At time 77.200
- Translation: [46.885, 45.869, 0.000]
- Rotation: in Quaternion [0.000, 0.000, 1.000, -0.022]
            in RPY [0.000, -0.000, -3.097]


Any thoughts on what might be happening?  It seems that tf_echo fails on the
first try but succeeds later on.

Help is appreciated.
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