[ros-users] Trouble converting points with TF

[Josh Faust]

Creating the listener in each call to the function means it will never have
any tf data in it.  You need to create it somewhere long-lasting and pass it
in to the function.

Josh

On Fri, Oct 22, 2010 at 4:51 PM, Daniel Chavez <dchavez at stanford.edu> wrote:

>
> 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.
> --
> View this message in context:
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