Hi, I've been trying to get a simulated turtlebot to map an area using the slamgmapping node. I'm more or less following the turtlebotstage tutorial from the ros wiki, using the turtlebotinstage.launch file, modified to use gmapping slamgmapping instead of mapserver. Everything's working ok, except that when my robot begins moving around, it starts 'warping' all over the place, according to the map it's building, and ends up creating a really bad looking map. On the rviz window which shows the robot's actual position, it looks fine, and so I'm not sure what the problem is. I've (I think) turned off the noise which stageros adds to the odometer readout, by setting its mean and standard deviations to zero in the map .world file, so I don't think that's the problem. Anyone have any insight into what might be going wrong?