[ros-users] slam_gmapping messages problem

Enea Scioni enea.scioni at student.unife.it
Fri Mar 26 16:28:22 UTC 2010


Dear ROS-users,
I'm trying to build a map using slam_gmapping stack but without success.
I tried before to download and use the test bag file and everything works
fine.
I'm using a sick lsm200 laser and a pioneer(peoplebot) platform and for make
my bag file I used the sicktoolbox_wrapper package (sicklms), a version
modified of p2os driver wrapper and the old package teleop_base (in
particular I'm using teleop_base_keyboard to send cmd_vel commands).

I don't know if I make a mistake when I'm trying to make a bag file, or on
the second step, when I'm trying to elaborate the bag file; anyway in the
tutorial
http://www.ros.org/wiki/slam_gmapping/Tutorials/MappingFromLoggedData I
read:
Start recording scans and transforms (note that the scan topic may vary from
robot to robot):
rosrecord -f mylaserdata /base_scan /tf

But maybe I didn't understand the meaning of "transforms". I know that for
make a map from slam algorithm I need to save/record laserdata and odometric
data; In my case, I've the following topics:
Published topics:
 * /motor_state [p2os/MotorState] 1 publisher
 * /battery_state [pr2_msgs/BatteryState] 1 publisher
 * /rosout [roslib/Log] 3 publishers
 * /rosout_agg [roslib/Log] 1 publisher
 * /pose [nav_msgs/Odometry] 1 publisher
 * /scan [sensor_msgs/LaserScan] 1 publisher
 * /cmd_vel [geometry_msgs/Twist] 1 publisher

Subscribed topics:
 * /time [unknown type] 4 subscribers
 * /rosout [roslib/Log] 1 subscriber
 * /cmd_vel [geometry_msgs/Twist] 1 subscriber
 * /cmd_motor_state [unknown type] 1 subscriber
 * /clock [unknown type] 4 subscribers

So I recorded scan and pose messagges in this way (note: I don't have a tf
topic message) :
record -f mylaserdata /scan /pose

After, When I'm try to make a map, I ran:
rosrun gmapping  slam_gmapping scan:=scan
(scan:=scan it's not necessary I think)
and I used the rosplay command as well:
rosplay mylaserdata-<data_info>.bag

After this, I received form slam_gmapping command this warning:
[ WARN] 1269617084.120287000: MessageFilter [target=/odom ]: Dropped 100.00%
of messages so far. Please turn the [ros.gmapping.message_notifier]
rosconsole logger to DEBUG for more information.

The warning it's correct (I send a odom messages) and it doesn't receive
information from scanner data, like in the test.bag example.
So I suppose that something in topic name is wrong, or better, the
slam_gmapping expects a tf message, as described in the ros wiki
http://www.ros.org/wiki/gmapping 5.1 Subscribed topics, where I read
"Transforms necessary to relate frames for laser, base, and odometry (see
below) " but "below" I didn't find information necessary for understand how
convert odometric message in a tf message and why I need to to this...

Anybody can help me?
Thank You!

Regards,
Enea Scioni

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