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2011-09-01 17:45:07 -0600 answered a question Converting laser_scan_matcher demo to use hokuyo node input

The demo.bag file only contains:

sensor_msgs/LaserScan [90c7ef2dc6895d81024acba2ac42f369]

topics: /scan 360 msgs : sensor_msgs/LaserScan

Are you getting any message from the laser scanner?

you can type: "rostopic hz scan"

to find out if the your laser scanner is publishing to ros correctly.

Can u also post your launch file?

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2011-08-29 20:46:21 -0600 commented answer What are the differences between stage and stageros ?
simulations in ros.
2011-08-29 20:46:05 -0600 commented answer What are the differences between stage and stageros ?
Nope, there's only one excutable for gazebo. stage is useful for 2D simulations. It's easier to setup and is good for simple model. However for more complex models, gazebo would be able to model them more accurately. You can take a look at the provided launch files to get an idea of how to launch
2011-08-28 17:18:07 -0600 answered a question What are the differences between stage and stageros ?

hmm good question. There are 2 stage executable files in the stage bin directory. stage and stageros.

stage is the one compiled from the original stage files. It can be used as the original stage simulator if the libraries are linked correctly. (By default the libraries are not linked for stage, the stage library has to be added to ldconfig)

However, stage does not provide the interface to ros. So if you use stage, the simulation data will not be available to ros although it will probably still work with player.

stageros on the other hand makes a portion of the stage interface available to ROS. It published the following topics to the ros interface, so that it would work with nodes written for ROS.







So if you want to run simulation in ros, you gotta use the stageros instead of stage; in order for ros to interpret the simulation data.

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2011-08-22 15:27:11 -0600 commented answer External Library Link Error
Can you post your edited CMakeLists.txt? And perhaps you might want to consider posing your comments as comments
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2011-08-17 15:18:18 -0600 answered a question storing 3d range data for localization

It depends on your needs. 3D would provide would allow you to localize in a 3D space. However there are other considerations.

Firstly, localizing in the a 3D space would increase the complexity of the localization problem. It would thus impose a significant computation load on the system.

Secondly, it would also takes more memory just to store a 3D map as opposed to a 2D map. say you have 10 points for 1D, that would be 100 points for 2D and 1000 points for 3D.

Thirdly, the laser scanner only provides 2D data. So you might need to get a tilting mechanism to be able to build a 3d pointcloud. Or use other kind of sensors such as a kinect camera.

Most of the time when you are driving you just need to know your 2D location. It's nice to know what's your height with reference to AMSL; and you can install a fancy altimeter in your car. However you probably won't be looking at it much, simply because you don't really need the data.

So at the end of the day, it really depends on your needs.

2011-08-17 04:59:37 -0600 commented question segmentation fault in reading PointCloud2 data from rosbag
Just to add on, i also encountered an error when trying to extract data from pointcloud2 that's playing back from a rosbag file. But the difference was me using the plot function from the rosbag gui and trying to export to cvs. They might be related but i can't be sure.
2011-08-17 04:53:56 -0600 answered a question Is there a laser assembler that produces PointCloud2?

although point_cloud_converter has been deprecated you can still use the package. It'll probably work just fine during the transition period till all the nodes has migrated to the new pointcloud2.

2011-08-16 23:59:55 -0600 answered a question Getting 11.0 as output data for all the scans when using pointcloud_to_laserscan node

Seems like it's because the pointclouds i have are assembled from a tilting laser scanner instead of a kinect camera. Therefore the direction conventions are different. I edited the direction conventions in the pointcloud_to_laserscan node and the laserscan are now published correctly.

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2011-08-15 17:21:20 -0600 edited question Getting 11.0 as output data for all the scans when using pointcloud_to_laserscan node

I have a bunch of pointcloud which i need to convert to laserscan. The data i have are in pointcloud and cannot be used directly. So i converted them to pointcloud2 using the point_cloud_converter and fed the pointcloud2 data to the CloudTOScan Nodelet. However the resulting published data is 11.0 for all the scans which corresponds to range_max + 1.0. I tried verifying the input data. Both the pointcloud and the converted pointcloud2 data can be viewed correctly in rviz. Any idea on what might be causing the issue?

2011-08-15 16:33:02 -0600 answered a question displaying point cloud in rviz from .bag files, error

Does the tf exists between the /base_link frame and /narrow_stereo_optical_frame?

You can verify this by adding "tf" in the rviz display, and checking the tf tree.

They should appear cascaded

/base_link (parent)

/narrow_stereo_optical_frame (child)

If it does exists try adding playing the rosbag with the clock command:

rosbag play -l refined_point_clouds.bag --clock

If that doesn't work, you might need to look at the actual setup from which the data was recorded.

2011-08-15 16:16:54 -0600 edited answer Problems with laser scan

1. Is your laser mounted on a mobile platform? If it is mounted low enough, the slight unevenness of the ground will cause the laser to tilt and the beam to be reflected off the ground. You can verify by the laser data by checking it when it is stationary.

2. check if the inflated obstacles are published correctly. if they are not, try checking the local costmap file params yaml file. make sure that the frames are correct.

global_frame: /odom

robot_base_frame: base_link

hope this helps

2011-08-15 16:06:39 -0600 commented answer cannot specify link libraries for target
in the target_link_libraries, there should be a space after ${BINNAME} , i've edited the original post to reflect the changes
2011-08-13 05:21:31 -0600 answered a question External Library Link Error

change the following line

from target_link_libraries(dssp dssp_rs232_drive_module)

to target_link_libraries(dssp /pathto/

where pathto is the path to ur file

2011-08-13 05:14:18 -0600 answered a question cannot specify link libraries for target

Change the lines with these, and make sure they are in the same order as shown.

rosbuild_add_executable (${BINNAME} ${SRCS})

target_link_libraries(${BINNAME} /pathto/

replace pathto with the full path to your library file

give it a try and let me know if it works for u.