  * ` --rate-control-topic=RATE_CONTROL_TOPIC `
    * watch the given topic, and if the last publish was more than ` <rate-control-max-delay> ` ago, wait until the topic publishes again to continue playback


` --output-dir=DIR `


To use your own custom message, you have to tell ROS about it when you build
your package. More specifically, ROS needs to generate the message headers and
put them in the proper location (depends on build tool). The [ Creating a Msg
and Srv tutorial
](http://wiki.ros.org/ROS/Tutorials/CreatingMsgAndSrv#Creating_a_msg) has the
steps for doing this, and it's explained in the [ msg wiki
](http://wiki.ros.org/msg#Building_.msg_Files) .


$ rosbag record --chunksize=1024 /chatter


  * [ rosbag ](namespacerosbag.html)
  * [ MessageInstance ](classrosbag_1_1MessageInstance.html)
Public Member Functions  |  Private Member Functions  |  Private Attributes  |
Friends  | [ List of all members ](classrosbag_1_1MessageInstance-
members.html)
rosbag::MessageInstance Class Reference
A class pointing into a bag file. [ More...
](classrosbag_1_1MessageInstance.html#details)
` #include < [ message_instance.h ](message__instance_8h_source.html) > `
##  Public Member Functions

---
std::string  |  [ getCallerId
](classrosbag_1_1MessageInstance.html#a19296e5b4cc26d55fc923be34bac211d) ()
const
[ boost::shared_ptr
](../../../../api/roscpp_traits/html/classboost_1_1shared__ptr.html) < [
ros::M_string
](../../../../api/cpp_common/html/namespaceros.html#a3d75f50002c0066a51761a9bc5102f2b)
> |  [ getConnectionHeader
](classrosbag_1_1MessageInstance.html#a31de14637302da546b91123b7d4fcd26) ()
const
std::string const & |  [ getDataType
](classrosbag_1_1MessageInstance.html#aff3b030c574f3d70ee1ab86d9c19ca60) ()
const
std::string const & |  [ getMD5Sum
](classrosbag_1_1MessageInstance.html#af90423336da62fe93fed7b870f3b8ddf) ()
const
std::string const & |  [ getMessageDefinition
](classrosbag_1_1MessageInstance.html#a9ade29c291e338a09835a961177d1569) ()
const
[ ros::Time ](../../../../api/rostime/html/classros_1_1Time.html) const & |  [
getTime
](classrosbag_1_1MessageInstance.html#ac5e6e1832200a77b1fe8b2434b150306) ()
const
std::string const & |  [ getTopic
](classrosbag_1_1MessageInstance.html#a2f64c79f7230d0579866d1457648f138) ()
const
template<class T >
[ boost::shared_ptr


[ example ](readmessages.html#buqn1u_-1)


The ROS Wiki is for ROS 1. Are you using ROS 2 ( [ Humble
](http://docs.ros.org/en/humble/) , [ Iron ](http://docs.ros.org/en/iron/) ,
or [ Rolling ](http://docs.ros.org/en/rolling/) )?
[ Check out the ROS 2 Project Documentation ](http://docs.ros.org)
Package specific documentation can be found on [ index.ros.org
](https://index.ros.org)


    * Suppress console output.

                $ rosbag record -q /chatter


    * Split the bag when maximum size or duration is reached

                $ rosbag record --split --size=1024 /chatter
        $ rosbag record --split --duration=30 /chatter
        $ rosbag record --split --duration=5m /chatter
        $ rosbag record --split --duration=2h /chatter


Command and output:


    * Record to bag with name NAME.bag.

                $ rosbag record -O session2_090210.bag /chatter


` -e ` , ` --regex `


  * ` --wait-for-subscribers `
    * wait for at least one subscriber on each topic before publishing


[ ![](/custom/images/brought_by_horiz.png) ](https://www.openrobotics.org/)


Load the rosbag.


  * ` --pause `
    * Start in paused mode.

                $ rosbag play --pause recorded1.bag


  * ` reindex <bag-files> `
    * Reindex the given bag files.

                $ rosbag reindex *.bag


####  ROS 2 Documentation


` -n ` , ` --noplugins `


` -k KEY ` , ` --key=KEY `


    * Show the usage and exit.

                $ rosbag decompress -h


If for some reason one of your ` rostopic ` processes missed the messages,
just kill its process with **Ctrl + C** , restart it, and call the ` rosbag
play ` command again.


Do you have the custom message installed already?


  * Immutable Page
  * Comments
  * [ Info ](/action/info/rosbag/Tutorials/reading%20msgs%20from%20a%20bag%20file?action=info)
  * [ Attachments ](/action/AttachFile/rosbag/Tutorials/reading%20msgs%20from%20a%20bag%20file?action=AttachFile)
  * More Actions:  Raw Text  Print View  Render as Docbook  Delete Cache  \------------------------  Check Spelling  Like Pages  Local Site Map  \------------------------  Rename Page  Copy Page  Delete Page  \------------------------  My Pages  Subscribe User  \------------------------  Remove Spam  Revert to this revision  Package Pages  Sync Pages  \------------------------  CreatePdfDocument  Load  RawFile  Save  SlideShow


    * Force overwriting of backup file it it exists.

                $ rosbag decompress -f *.bag


  * ` topic `
    * the topic of the message


**Note:** This tutorial assumes that you have completed the previous
tutorials: [ Recording and playing back data
](/rosbag/Tutorials/Recording%20and%20playing%20back%20data) .
---

![\(!\)](/moin_static197/rostheme/img/idea.png) Please ask about problems and
questions regarding this tutorial on [ answers.ros.org
](http://answers.ros.org) . Don't forget to include in your question the link
to this page, the versions of your OS & ROS, and also add appropriate tags.
---

#  Reading messages from a bag file


    import rosbag
    import rospy  # Need this to create a rospy.Time object for Event.ts
    from std_msgs.msg import Int32, String
    from dvs_msgs.msg import Event  # Imports the custom message from its package

    bag = rosbag.Bag('test.bag', 'w')

    try:
        s = String()
        s.data = 'foo'

        i = Int32()
        i.data = 42

        e = Event()
        e.x = 23
        e.y = 17
        e.ts = rospy.Time.now()
        e.polarity = False

        bag.write('chatter', s)
        bag.write('numbers', i)
        bag.write('events', e)
    finally:
        bag.close()


That's it! You'll see it print out all 70 messages quickly. Here is what the
last little bit of the terminal output looks like:


[ ![Asdewar gravatar image](/m/default/media/images/nophoto.png?v=28)
](/users/71807/asdewar/) [ Asdewar ](/users/71807/asdewar/) (  2021-03-17
07:11:23 -0500  )  edit


  * [ fix ](/rosbag/Commandline#fix)
    * Repair the messages in a bag file so that it can be played in the current system.


  * [ info ](/rosbag/Commandline#info)
    * Summarize the contents of a bag file.


  * ` --hz=HZ `
    * Publish clock time at frequency HZ Hz (default: 100).

                $ rosbag play --clock --hz=200 recorded1.bag


Currently, there are two supported formats: [ BZ2 ](http://www.bzip.org) and [
LZ4 ](https://lz4.github.io/lz4) . BZ2 is selected by default. Which should
you prefer? BZ2 generally produces smaller bags than LZ4, so use it if disk
usage is your primary concern. However, BZ2 is typically much slower than LZ4,
both during compression and later when a bag's chunks are decompressed for
reading, so use it if you're willing to tolerate slightly larger bags. [ Look
here ](https://github.com/ros/ros_comm/pull/356) a more detailed discussion
and some benchmarks.


    * Print information only on the given field (requires ` -y ` ).

                $ rosbag info -y -k duration /path/to/my.bag


###  **Create rosbag Selection Using** **` rosbagreader ` ** **Object**


  * ` play <bag-files> `
    * Play back (publish) the contents of the given bags.

                $ rosbag play recorded1.bag recorded2.bag


##  How to Get Best Site Performance


` -q ` , ` --quiet `


Return the first ten messages as a cell array.


Return all messages as a cell array.


` rosbag decompress ` is a command-line tool for decompressing bag files. It
automatically determines which compression format a bag uses.


[ tags ](/tags/) [ users ](/users/) [ badges ](/badges/)


    * Show the usage and exit.

                $ rosbag filter -h


##  Comments


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Follow


You can now create messages as structures with fields matching the message
object properties. Using structures typically improves performance of
creating, updating, and using ROS messages, but message fields are no longer
validated when set. Message types and corresponding field values from the
structures are validated when sent across the network.


Main Content


  * ` --topics `
    * specify which topics to play back

                $ rosbag play recorded1.bag --topics /topic1 /topic2 /topic3


[ Source: this material was adapted from instructions first published in this
document here.
](https://github.com/ElectricRCAircraftGuy/eRCaGuy_dotfiles/blob/master/git%20%26%20Linux%20cmds%2C%20help%2C%20tips%20%26%20tricks%20-%20Gabriel.txt)


##  rosbag check


` -a ` , ` --append `


Someone knows how to write it in the bag file?


If a bag is currently unplayable and non-migratable, it may be necessary to
generate rules to bring the bag up to date. See [ Migrating Messages
](/rosbag/migration) for the preferred approaches to doing this.


` --udp `


` -a ` , ` --all `


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Hello everybody/ I'm new in ros and possible my question is very stupid. But
i've read huge amount of tutotials and posts on forum and still have
questions. I'm really stack with my task to setup 2 6dof robot on scene, I
cant figure out how to publush transform between robot base and world when
each robot has it own namespace and tf_prefix. So what I have: I have two 6dof
robot setup on table, camera and the box. I whant to detect box from camera
and publish box's coordinates in table/world coordinate system. Each robot
listen there coordinates topic and transform coordinates of the box in there
own frame, then robot touch a box. What I did. I can get the position of box
in camera frame and tranform it robot frame. But it transform likes robot base
in the [0,0,0] world frame. So I cant publish in TF static transformation from
robot base to the zero point, I run static_tranform_publisher node for that
but in tf tree I can't see the root node. So my questions is: \- if there some
recommended way to use namespases with MoveIt and Rviz? \- how could I build
and set the "world" for scene from several frames. Thanks a lot in advance and
sorry if it common question. Any information about topic would be very
appripricate.


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estimated offset from the ` map ` to the ` odom ` frame to publish the
transform from ` earth ` to ` map ` frame.
##  Transitions Between Maps
When a robot travels a long distance it is expected that it will need to
transition between maps. In an outdoor context map coordinate frame is a
euclidian approximation of a vicinity however the euclidian approximation
breaks down at longer distances due to the curvature of the earth. In an
indoor context this can be transitioning between two buildings where each has
a prior map in which you are navigating or the robot is on a new floor of a
building.
It is the responsibility of the localization frame authority to reparent the `
odom ` frame appropriately when moving between maps. The common implementation
of computing the ` map ` to ` odom ` frame as the results of subtracting the `
odom ` to ` base_link ` from the localization fix ` map ` to ` base_link `
will take care of this implicitly when the choice of which ` map ` frame
changes.
**odom Frame Consistency**
When transitioning between maps the odometric frame should not be affected.
Data retention policies for data collected in the odom frame should be tuned
such that old or distant data is discarded before the integrated position
error accumulates enough to make the data invalid. Depending on the quality of
the robot's odometry these policies may be vastly different. A wheeled vehicle
with multiple redundant high resolution encoders will have a much lower rate
of drift and will be able to keep data for a much longer time or distance than
a skid steer robot which only has open loop feedback on turning.
There are other contexts which will also affect appropriate retention policy,
such as the robot being moved by external motivators, or assumptions of a
static environment. An example is a robot in an elevator, where the
environment outside has changed between entering and exiting it. Most of these
problems come from the assumption of a static environment where observations
are in the same inertial frame as the robot. In these cases semantic
information about the environment and its objects is required to manage
persistent data correctly. Regardless, the inertial odom frame should always
remain continuous.
If the vehicle travels a long enough distance that the distance from the `
odom ` frame's origin to the vehicle approaches the maximum floating point
precision, degraded performance may be observed for float-based data persisted
in the ` odom ` frame. This is especially true of 32-bit floating point data
used in things like pointclouds. If distances on this order are encountered a
systematic reset of the ` odom ` frame origin may be required. If centimeter


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Finally, we can launch RViz again, add the TF visualisation, and see our
frames move as we adjust the sliders. We can also add a “RobotModel”
visualisation in RViz. Use the options to select ` /robot_description ` as the
topic, and a visual representation of the links should appear.


April 18, 2024, 11:05 am


In the URDF file each joint can be defined as “fixed”, or one of a variety of
movable types (e.g. continuous spinning, limited rotation, linear sliding).
For the joints that are fixed, ` robot_state_publisher ` can just publish a
static transform, but for the ones that move it needs an external value (e.g
an angle or distance) to calculate the dynamic transform for that point in
time. To get these values, it subscribes to a topic called ` /joint_states ` ,
which will contain ` JointState ` messages. These messages can contain
information about the position, velocity, or effort of a joint (but for now we
will only use position).


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Howdy folks, I have question relating to the following transform tree:
**[/nav_frame]->[/base_link]->[/sensor_platform] -> [/IMU_AHRS]** The sensor
platform is literally a platform that has sensors mounted on it (GPS antenna,
IMU-AHRS, etc.) and is attached to the robotic platform (/base_link). The
nav_frame is a local ENU frame in which I do my navigation computations: it's
placed on the WGS84 ellipsoid at the same location as the base_link, and it
always points north. I got an IMU-AHRS system (with magnetometer and world
magnetic map) mounted on the sensor_platform that I will use to resolve the
transformation between nav_frame and base_link. So, I have the following
situation: [/nav_frame]->[/base_link] UNKNOWN, this is what I need to resolve
[/base_link] ->[/sensor_platform] is a known and fixed transform
[/sensor_platform] -> [/IMU_AHRS] is a known and fixed transform **My
Question: Can tf (or tf2) somehow automatically (internally) resolve the
hidden transform [/nav_frame]->[base_link] when it's given the measured
transform [/nav_frame] -> [/IMU_AHRS] as produced by the IMU-AHRS system, or
do I (as the programmer) have to explicitly compute this transform (which is
easy enough using the IMU-AHRS measurements and the fixed transforms relating
the IMU_AHRS frame w.r.t. the base_link) and explicitly publish this as the
[/nave_frame] -> [/base_link] transform?** if tf/tf2 can do this "internally",
then how? Thanks in advance Best regards, Galto


ROS provides a system called ` tf2 ` (TransForm version 2) to handle these
transformations for us. Any node can use the ` tf2 ` libraries to _broadcast_
a transform from one frame to another. As mentioned above, these transforms
will need to form a tree structure, where each frame is defined by one (and
only one) transform from another frame, but can have any number of frames
dependent on it. The picture below shows a portion of a tree that we’ll be
exploring later. In this tree, ` base ` and ` camera ` are defined relative to
` world ` , and ` l3 ` is defined relative to ` base ` .


![Skid-steering mechanism for wheeled mobile
robots](data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==)
![Skid-steering mechanism for wheeled mobile
robots](https://kshitijtiwari.com/wp-content/uploads/2023/07/skid-
steering-1024x538.png)


![Fixing reference frame](/media/assets/posts/ready-for-
ros/tf_screenshot_fix_frame.png)


October 8, 2011, 10:58 am


Then, to publish the joint states, we can run


As mentioned earlier, the transform data is published across two topics, ` /tf
` and ` /tf_static ` . We can try to listen to these topics directly using `
ros2 topic echo ` , but that can sometimes be tricky to interpret. To help,
ROS comes with a tool (do we need to install ` tf2_tools ` ?) called `
view_frames ` that lets us visualise the transform tree, along with
information about how it is being broadcast.


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> Note that RViz represents the transform as an arrow from child to parent,
> rather than parent to child as in the introduction and in ` view_frames `
> below.


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##  Ackermann Robot Steering


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In URDF, a robot is made up of a series of rigid components called _links_ ,
and the links are joined together in a parent-child tree structure, where the
relationships between different links are called _joints_ . Seem familiar?


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![TF Scene 2](/media/assets/posts/ready-for-ros/tf_scene_2.png)


###  Wheel Slippage


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4. Mecanum Robot Steering


##  Under the hood


It’s good to play around with this and get a feel for how transforms work. Try
changing the fixed frame (top-left) to be one of the robots instead of ` world
` , adjusting the frames to new positions and rotations, or adding some new
ones.


August 15, 2017, 10:52 am


#  [ Best practices for tf?
](//question2177.rssing.com/chan-36149602/article528-live.html)


The ROS transform system is a powerful tool and we’ve only just scratched the
surface of how we can use it. The details of how we use TF will depend on many
factors such as whether our robot is mobile, or a manipulator (or a mobile
manipulator), and whether we are running simulations or on physical hardware.
In future tutorials we’ll look more closely at how TF can be used for
particular projects.


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In conclusion, the steering mechanism is a critical component of mobile
robots, influencing their movement and capabilities. As technology continues
to advance, we can expect further innovations in steering mechanisms, enabling
robots to navigate even more complex and dynamic environments. Albeit,
challenges like [ operational range estimation
](https://kshitijtiwari.com/all-resources/mobile-robots/range-estimation/) to
avoid complete immobilization during the mission still remain.


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    ros2 run tf2_tools view_frames.py

---|---
`


      * map
      * earth
    * Relationship between Frames
    * Example of multi-robot tf graph using ECEF
    * Frame Authorities
    * Transitions Between Maps
    * Exceptions
  * Compliance
  * References
  * Copyright
#  Abstract
This REP specifies naming conventions and semantic meaning for coordinate
frames of mobile platforms used with ROS.
#  Motivation
Developers of drivers, models, and libraries need a share convention for
coordinate frames in order to better integrate and re-use software components.
Shared conventions for coordinate frames provides a specification for
developers creating drivers and models for mobile bases. Similarly, developers
creating libraries and applications can more easily use their software with a
variety of mobile bases that are compatible with this specification. For
example, this REP specifies the frames necessary for writing a new
localization component. It also specifies frames that can be used to refer to
the mobile base of a robot.
#  Specification
##  Coordinate Frames
###  base_link
The coordinate frame called ` base_link ` is rigidly attached to the mobile
robot base. The ` base_link ` can be attached to the base in any arbitrary
position or orientation; for every hardware platform there will be a different
place on the base that provides an obvious point of reference. Note that REP
103  [1]  specifies a preferred orientation for frames.
###  odom
The coordinate frame called ` odom ` is a world-fixed frame. The pose of a
mobile platform in the ` odom ` frame can drift over time, without any bounds.
This drift makes the ` odom ` frame useless as a long-term global reference.
However, the pose of a robot in the ` odom ` frame is guaranteed to be
continuous, meaning that the pose of a mobile platform in the ` odom ` frame
always evolves in a smooth way, without discrete jumps.
In a typical setup the ` odom ` frame is computed based on an odometry source,
such as wheel odometry, visual odometry or an inertial measurement unit.


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![Viewing TF tree structure](/media/assets/posts/ready-for-ros/tf_frames.png)


Shown below are two examples of robotic systems where transformations are
helpful. In the first, two mobile robots are exploring and one has found an
object of interest. How will the other robot know how to get to it? In the
second, a mounted camera has spotted a target and a manipulator needs to move
the gripper over to it. How do we know the correct motion from the gripper to
the target?


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Steering robots, or programmable steering controllers, apply precise,
repeatable inputs to a test vehicle's steering system. Applications include
the development of advanced driver assistance systems (ADAS) and electronic
stability control (ESC) systems, as well as self-driving cars and other
autonomous vehicles.


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##  Deployment challenges with wheeled robots


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If we have a system where every frame is defined by its relationship to one
(and only one) other frame, this will create a _tree structure_ , and we will
be able to convert a known point in one frame to any other frame in the tree.


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The script is part of the ` tf2_tools ` package, so all we need to do is run:


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We can configure the data displayed in RViz using the left panel. For example,
we can open up the settings for the TF visualisation and enable displaying
frame names.


Wheel sinkage refers to the sinking of wheels into soft or loose terrains,
such as sand, mud, or gravel. When the wheels sink into the ground, the
robot’s mobility and maneuverability are affected, as the resistance from the
terrain increases. This can lead to difficulties in traversing through such
environments and may even result in the robot getting stuck.


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can only have one parent.
**Extra Intermediate Frames**
This graph shows the minimal representation of this graph. The basic topology
should stay the same, however it is fine to insert additional links in the
graph which may provide additional functionality.
**Pressure Altitude**
An example of a potential additional coordinate frame is one to represent
pressure altitude for flying vehicles. Pressure altitude is an approximation
of altitude based on a shared estimate of the atmospheric barometric pressure.
[5]  In flying applications pressure altitude can be measured precisely using
just a barometric altimeter. It may drift in time like odometry but will only
drift vertically. To be useful a ` pressure_altitude ` frame could be inserted
between the inertially consistent ` odom ` frame and the ` map ` frame. There
would need to be an additional estimator to estimate the offset of the `
pressure_altitude ` from the ` map ` but this extra coordinate frame can
support extra functionality and does not break the abstraction outlined above.
##  Example of multi-robot tf graph using ECEF
%% Example diagram graph TB odom_1(odom_1) --> base_link1(base_link1)
map_1(map_1) --> odom_1 earth(earth) --> map_1 odom_2(odom_2) -->
base_link2(base_link2) map_2(map_2) --> odom_2 earth --> map_2
This is an example of a tf tree with two robots using different maps for
localization and having a common frame ` earth ` .
The diagram above uses different frame ids for clarity. However for maximum
reusability it is recommended to use the canonical frame ids on each robot and
use a script to forward information off of the robot. When the information is
forwarded the frame ids should be remapped to disambiguate which robot they
are coming from and referencing.
##  Frame Authorities
The transform from ` odom ` to ` base_link ` is computed and broadcast by one
of the odometry sources.
The transform from ` map ` to ` base_link ` is computed by a localization
component. However, the localization component does not broadcast the
transform from ` map ` to ` base_link ` . Instead, it first receives the
transform from ` odom ` to ` base_link ` , and uses this information to
broadcast the transform from ` map ` to ` odom ` .
The transform from ` earth ` to ` map ` is statically published and configured
by the choice of map frame. If not specifically configured a fallback position
is to use the initial position of the vehicle as the origin of the map frame.
If the map is not georeferenced so as to support a simple static transform the
localization module can follow the same procedure as for publishing the


If we go back to our first terminal, and rerun the command with a larger
rotation of 90° (1.57 rad), we should see in RViz that the first robot’s
marker rotates, and the second robot moves too because its frame is defined
relative to the first robot.


I need a bag file for laser scanner data. The bag file should have a node
publishing tf2_msgs/TFMessage and sensor_msgs/LaserScan type messages to
topics. I started out with this tutorial - [Introduction to Working With Laser
Scanner
Data](http://wiki.ros.org/laser_pipeline/Tutorials/IntroductionToWorkingWithLaserScannerData#Converting_a_Laser_Scan_to_a_Point_Cloud)
but the bag file provided here has odometry data (nav_msgs/Odometry type
message). I just don't understand how to transform odometry data to tf data.
Either help is appreciated.


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September 11, 2017, 10:43 pm


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![Static TF Visualisation](/media/assets/posts/ready-for-
ros/tf_screenshot_static_1.png)


    ros2 run tf2_ros static_transform_publisher 2 1 0 1.57 0 0 world robot_1

---|---
`


The ` view_frames ` tool is actually a Python script which listens to the
transforms for a few seconds, then generates a file called ` frames.pdf ` (and
also ` frames.gv ` ) in whatever directory the terminal was in when the script
was executed (for a fresh terminal this will be your home directory).


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I have multiple tf frames which some of are dynamically published by the
robot_state_publisher and some are static transformations. When using the
tf.TransformListener i get the error message that there are two or more
unconnected trees. Running rosrun tf view_frames also shows the unconnected
trees. However, rosrun rqt_tf_tree rqt_tf_tree shows the correct tf tree, rviz
can show the correct tf tree and even rosrun tf tf_echo source_frame
destination_frame returns the transformation values. What am I doing wrong?
EDIT1: rosrun tf tf_monitor source_frame target_frame returns the correct
chain, however every frame is published by "unknown publisher" and the only
broadcaster node is called "unknown". Could this be the reason why view_frames
or the TransformListener are failing? EDIT2: TF2 can do the transformation
with the following piece of code: tf_buffer = tf2_ros.Buffer() tf2_listener =
tf2_ros.TransformListener(tf_buffer) tf_buffer.lookup_transform('world',
'halcon_camera', rospy.Time())


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2. Ackermann Robot Steering


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Originally developed by PMW for an actuator for a bomb disposal robot, the
modified motor retains the same winding specifications but incorporates a
different shaft and a bespoke casing that integrates directly into the Anthony
Best Dynamics steering robot.


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**Omni-directional steering** mechanisms offer the most flexibility and
versatility in terms of maneuverability.  Omni wheels feature small, freely
rotating wheels around the main drive wheels, allowing the robot to move in
any direction without changing its orientation. This holonomic steering
mechanism provides excellent maneuverability, making it ideal for navigating
tight spaces and performing agile movements. Omni wheels are commonly used in
applications such as warehouse automation, robotic arms, and omnidirectional
robots.


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    ros2 run robot_state_publisher robot_state_publisher --ros-args -p robot_description:="$(xacro path/to/my/xacro/file.urdf.xacro)"

---|---
`


![URDF TF comparison](/media/assets/posts/ready-for-ros/urdf_tf.png)


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I am following this tutorial
[here](http://wiki.ros.org/laser_pipeline/Tutorials/IntroductionToWorkingWithLaserScannerData)
for understanding how to use laserscanner data. There is a bag file which
publishes laser scan data alongside odometry data. So it doesn't publish
anything on /tf topic but gives out Odometry message. Is there a way to
convert that Odometry info to TF ? I have rosbag file which Is there a way to
convert that odometry data to tf?


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To overcome wheel sinkage, wheeled robots can be equipped with larger wheels
or add-ons like wheel extensions or tracks that distribute the robot’s weight
over a larger surface area. By increasing the contact area with the ground,
the robot can minimize sinking and improve its ability to navigate challenging
terrains.


##  Transforms in ROS


##  Viewing Frames and Transforms in RVIZ


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Coordinate transformations (or transforms) play a huge role in the mathematics
of robotics. They are a a mathematical tool to take points or measurements
that are represented from one point of view, and represent them in a different
point of view that is more useful. Without using transformations, we would
need to perform the calculations with trigonometry, which quickly becomes very
complex with larger problems, and especially in 3D.


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I have seen quaternions in tf and bullet but I don't know what they are or how
to use them.


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September 7, 2017, 4:47 am


April 8, 2024, 1:08 pm


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You might expect the ` robot_description ` parameter to be a path to a URDF
file, but it actually expects the full _content_ of the URDF file to be passed
in at the command line. To achieve this we need to use the ` xacro ` software
on the URDF to preprocess it, run that inside a subshell ( ` $(...) ` ), and
enclose it in quotes ( ` "..." ` ) so that the spaces don’t break everything.
So our run command will look more like:


I'm wondering if there is a good way to get transforms (rotation and
translation) from tf data recorded in bag files. I'm working in python and I
don't want to replay the bag file as part of the solution. Instead I want to
be able to get other messages from the bag file and use tf to find the
euclidean distance between two frames on the robot at the same time instant as
my message of interest. Any thoughts? I could look at parent-child
relationships in a single tf message and string the transforms together, but
then I'd be recreating the functionality of tf. Is there a utility or tool for
getting a transformation from a single tf message (i.e. not using ROS to wait
for transform or having to replay the bag file). Thanks a lot for any ideas.


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Let’s pretend we have a second robot that always sits to the right of our
first one (like a sidecar). Using a second terminal, we can create another
static transform using the command below to create a new frame, ` robot_2 `
that sits 1m in the positive x direction of ` robot_1 ` .


To mitigate wheel slippage, several strategies can be employed. One approach
is to use wheels with high-friction materials or specialized tire treads that
provide better grip on different surfaces. Implementing traction control
algorithms can also help regulate wheel motion and optimize the robot’s
ability to navigate challenging terrains.


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November 22, 2016, 10:52 pm


I recorded tf-messages (while driving the robot) into a bagfile and wrote a
ros node that should extract the positions (base_link-frame) from that bag
file. My idea was to use a tf::Transformer and feed it with all the transforms
stored in the tf-messages: rosbag::Bag bag; bag.open("tf.bag",
rosbag::bagmode::Read); std::vector<:string> topics; topics.push_back("/tf");
rosbag::View view(bag, rosbag::TopicQuery(topics)); tf::Transformer
transformer; BOOST_FOREACH(rosbag::MessageInstance const m, view) {
//instantiate bag message tf::tfMessage::ConstPtr tfPtr =
m.instantiate<:tfmessage>(); BOOST_FOREACH(geometry_msgs::TransformStamped
const tfs, tfPtr->transforms) { tf::StampedTransform stampedTf;
tf::transformStampedMsgToTF(tfs, stampedTf); //setTransform returns true!
transformer.setTransform(stampedTf); ... } } The method setTransform(...)
always returns true, so I thought that it works... Each time I get a transform
with child_frame == /robot_1/base_link I want to get the map-base_link-
transform at the time of this last transform. But the transformer returns
false: if(transformer.canTransform(baseLink, mapFrame,
stampedTf.stamp_)==true){ //lookup transform
transformer.lookupTransform(baseLink, mapFrame, stampedTf.stamp_, temp); } A
few additional facts: The transformer's latest common time is always = 0:
transformer.getLatestCommonTime(baseLink, mapFrame, time, NULL) And printing
all tf-messages of the bag shows that the tf-tree should be consistent (I'm
using stage and used view_frames): /map -> /robot_1/odom ->
/robot_1/base_footprint -> /robot_1/base_link -> /robot_1/base_laser_link Is
something wrong with my code or idea? Any suggestions for a better solution?
Thanks in advance!


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** Mecanum steering  ** is a unique and versatile mechanism used in mobile
robots. It involves four wheels, each with a set of rollers mounted at an
angle  making it slightly different from the omni-wheels  . By rotating these
wheels independently and in different directions, the robot can move in any
direction, including sideways and diagonally. This omnidirectional movement
capability makes mecanum steering ideal for applications where precise
maneuverability is required, such as robotic arms or autonomous vehicles in
tight spaces. However, the complexity of the mechanism and the increased
number of wheels make it less efficient and more expensive than other steering
mechanisms.


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> Note, in ROS 1 there was a useful tool called ` rqt_tf_tree ` which did
> exactly this but with less hassle. At time of writing, however, this hasn’t
> been ported to ROS 2, and so we have to use ` view_frames ` instead.


> This tutorial is all about how ROS makes using transformations simple. If
> you’re particularly interested in the more complex and interesting
> underlying mathematics, I’ve written (most of) a series of tutorials on
> them, available _here_ .


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Given I have an occupancy grid map which I would want to transform with a
certain [tx,ty,theta] transformation. How do I do it? The tf tree is posted
below and also the rviz which contains the grid map. My ultimate goal is that
I would have two occupancy grid maps which I would have to apply a
transformation to either one of them so that they can be overlapped -- Map
Merging. I'm looking for the mechanism in ROS where I can transform the map,
particularly the whole /tf frame so that even the robot's pose will be
transformed into a new coordinate frame. http://postimg.org/image/d4xd3d39p/
http://postimg.org/image/vrdqce6x9/


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  5. Omni-directional Robot Steering
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August 12, 2017, 5:33 am


##  Skid-Steering


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We’ve learnt some cool tricks so far, but we’re still stuck publishing static
frames. We want our robot to move! Before we tackle this we need to install a
couple of extra packages:


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August 8, 2017, 7:07 am


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It’s not too hard to see how the link/joint pattern is very similar to the
frame/transform pattern. Because they are so tightly related, there is a ROS
node called ` robot_state_publisher ` which can take in a URDF file and
automatically broadcast all the transforms from it. It will also publish the
full contents of the URDF file to the topic ` /robot_description ` so that any
other nodes that need it can all use the same file.


Hi, I'm unable to lookup tf transforms in my C++ node for some reason, unless
the parent and child are the same. I have done this many times before and
checked with the tutorials and wikis but am not having any luck. The tf tree
displays fine in RVIZ as well as command line with the tf_echo. I've tried
multiple different rosbags that worked fine in other ROS nodes but nothing is
working with this node. What is different is that this time I am working with
a ROS package where there are no classes, everything is in functions but I
don't think that should matter because that is how the tutorial is done. Here
is a code snippet: void laserCloudHandler(const
sensor_msgs::PointCloud2ConstPtr &laserCloudMsg) { tf::TransformListener
tf_listener; if (tf_listener.waitForTransform("world", "velodyne_frame",
laserCloudMsg->header.stamp, ros::Duration(0.2))) { // Get the tf transform.
tf::StampedTransform tf_transform; tf_listener.lookupTransform(world_frame,
velo_frame, laserCloudMsg->header.stamp, tf_transform); } else {
ROS_FATAL("UNABLE TO LOOKUP INITIAL TRANSFORM!"); } } Does anyone have any
idea what may be wrong? Thanks!


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    ros2 run tf2_ros static_transform_publisher 2 1 0 0.785 0 0 world robot_1

---|---
`


Furthermore, advanced navigation techniques, such as simultaneous localization
and mapping (SLAM), can enhance the robot’s ability to accurately map and
perceive its environment, aiding in avoiding potential slippage and sinkage
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Wheel slippage occurs when the wheels of a robot lose traction and fail to
maintain the desired motion. It can happen on slippery surfaces, uneven
terrains, or when the robot encounters obstacles. Slippage can lead to
inaccuracies in robot localization, reduced maneuverability, and compromised
control over the robot’s movements.


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Hey guys, I am all in all pretty new to computer science in general and
learning ROS now. came across some tutorials on tf after completing the
beginner tutorials. I want to use rososc but that's another story since it is
not updated for kinetic and catkin and I'm still trying to work out how to
make that work for me... anyway, -explain what tf is used for as if I am a 5
year old. -why would I use it in developing robots? -what type of applications
is it useful for?


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I see other similar questions here, but nothing that answered my specific
inquiries about tf: 1\. Is it recommended to use a separate tf server (as in
its own node)? 1\. Should URDF be used for statically-linked robots like
quadcopters with a few attached sensors? 1\. When is a tf_state_publisher used
(from a launch file, say), as opposed to a tf broadcaster in code?


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REP:  |  105
---|---
Title:  |  Coordinate Frames for Mobile Platforms
Author:  |  Wim Meeussen
Status:  |  Active
Type:  |  Informational
Content-Type:  |  [ text/x-rst ](https://ros.org/reps/rep-0012.html)
Created:  |  27-Oct-2010
Post-History:  |  27-Oct-2010

* * *
Contents
  * Abstract
  * Motivation
  * Specification
    * Coordinate Frames
      * base_link
      * odom


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May 17, 2011, 7:59 am


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** Skid  –  steering  ** is a mechanism often used in smaller mobile robots.
It involves controlling the speeds and directions of the left and right set of
wheels (group) independently, similar to  differential steering  . However,
instead of varying the speed of each wheel to turn, skid-steer steering relies
on driving the wheels on one side of the robot in opposite directions. This
causes the robot to pivot around a point between the wheels, allowing for
tight turns and maneuverability in confined spaces. Skid-steer steering is
commonly seen in robots like rovers and tank-like vehicles. However, it can be
less efficient and prone to slipping on certain surfaces.


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    ros2 run rviz2 rviz2

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August 29, 2017, 2:46 am


"Printed Motor Works took a complex design, generated production drawings and
manufactured it to meet all our performance requirements," said Colin Martin,
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Hopefully the above example worked, but sometimes when we’re working with
transforms things aren’t working properly and we need to figure out why.


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1. Differential Robot Steering


##  Conclusion


[ ](javascript:; "Ouch") 0


When using wheeled robots, one common challenge that arises is wheel slippage
and sinkage, which can significantly impact their performance and mobility.
Understanding these challenges is crucial for effective deployment and
operation of wheeled robots in various environments.


April 14, 2024, 8:14 am


level accuracy is required the maximum distance to the ` odom ` frame is
approximately 83km.  [6]  There is not a standard solution to this, systems
with this issue will need to work around it. Potential solutions include
additional coordinate frames in which to persist obstacle data or to store
obstacle data, or using higher precision.
##  Exceptions
The scope of potential robotics software is too broad to require all ROS
software to follow the guidelines of this REP. However, choosing different
conventions should be well justified and well documented.
#  Compliance
This REP depends on and is compliant with REP 103  [1]  .
#  References
[1]  |  _( 1  ,  2  ) _ REP 103, Standard Units of Measure and Coordinate
Conventions ( [ http://www.ros.org/reps/rep-0103.html
](http://www.ros.org/reps/rep-0103.html) )
---|---
[2]  |  Earth Centered, Earth Fixed Wikipedia article ( [
https://en.wikipedia.org/wiki/ECEF ](https://en.wikipedia.org/wiki/ECEF) )
---|---
[3]  |  Mean Sea Level ( [ https://en.wikipedia.org/wiki/Sea_level
](https://en.wikipedia.org/wiki/Sea_level) )
---|---
[4]  |  EGM1996 ( [ http://earth-
info.nga.mil/GandG/wgs84/gravitymod/egm96/egm96.html ](http://earth-
info.nga.mil/GandG/wgs84/gravitymod/egm96/egm96.html) )
---|---
[5]  |  Pressure Altitude ( [ https://en.wikipedia.org/wiki/Pressure_altitude
](https://en.wikipedia.org/wiki/Pressure_altitude) )
---|---
[6]  |  Floating Point Precision ( [ https://en.wikipedia.org/wiki/Single-
precision_floating-point_format ](https://en.wikipedia.org/wiki/Single-
precision_floating-point_format) )
---|---

#  Copyright
This document has been placed in the public domain.


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After running gmapping from intel.bag, while generating the map, if I run
rosrun tf view_frames, it gives me the frames.pdf. In this case, the transform
is map->odom->base_link and odom->laser,the broadcasting node for map->odom is
/slam_gmapping, the broadcasting node for odom->laser is
/play_1479118047019813325 node, the broadcasting node for odom->base_link is
/static_transform_publisher_1479118028670611586 node Please explain the tree.


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In ROS 2, RViz (the ROS visualisation tool) is called ` rviz2 ` , and is in a
package with the same name. So we just need to run:


** Ackermann  ** **steering,** sometimes also referred to as [ Rack & pinion
steering
](https://mae.ufl.edu/designlab/class%20projects/background%20information/steering.htm)
**__,_ _ ** is another popular steering mechanism that provides better
maneuverability and stability compared to differential steering. This
mechanism uses a steering angle for each wheel, calculated based on the
desired turn radius. By adjusting the steering angles, the robot can make
precise turns without skidding or slipping. Ackermann steering is commonly
used in vehicles such as cars and trucks, where precise steering control is
necessary. However, it may not be suitable for all types of mobile robots,
especially those with limited space for steering mechanisms.


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August 23, 2017, 7:39 am


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Any node can also use the ` tf2 ` libraries to _listen_ for transforms, and
then use the transforms to convert points from any frame to any other frame,
as long as they are connected in the tree.


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September 7, 2017, 2:11 am


If we’re writing our own nodes, we can code them to broadcast whatever
transforms we like, but most of us starting out aren’t ready to write custom
nodes or calculate transforms. To help with this, ROS comes with some built-in
nodes that perform some common broadcasting tasks.


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Is robot_state_publisher designed to handle multiple sources of /joint_state
information? For example, let's say I have the R2D2-like robot from this
[tutorial](http://wiki.ros.org/urdf/Tutorials/Using%20urdf%20with%20robot_state_publisher).
If I have one node publishing the state of the 'periscope' on `/joint_states`,
and another node publishing the rest of the joints, also on `/joint_states`,
will `robot_state_publisher` do the right thing? (i.e., 'merge' the
`/joint_state` messages?). I'm currently studying the source code to
definitively figure this out, but I see that others have asked this in the
past, so I figured I'd raise the issue again.


##  Differential Robot Steering


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#  Getting Ready for ROS Part 6: The Transform System (TF)


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The command below will broadcast a static transform, with the translations and
rotations provided, from ` parent_frame ` to ` child_frame ` . Note that the
rotations are in radians, and are processed after the translations, in order,
with respect to the local coordinate system.


###  Wheel Sinkage


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##  Omni-Directional Robot Steering


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August 12, 2017, 6:09 am


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    ros2 run joint_state_publisher_gui joint_state_publisher_gui

---|---
`


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The system helps provide a repeatable test environment for quantitative
testing of road vehicles on the track. The compact design of the motor enables
the assembly to be mounted behind the steering wheel, allowing normal driver
operation between tests. The three-phase permanent magnet motor is a
customised version of PMW's IR9 series. Its conventional internal rotor design
combined with dovetailed NdFeB rare earth magnets gives it exceptional
performance and long service life.


##  Mecanum Robot Steering


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**Differential steering** is one of the most common steering mechanisms used
in mobile robots. It involves controlling the speeds of the left and right
wheels independently, allowing the robot to turn by varying the speed of each
wheel. This mechanism is simple and efficient, making it suitable for many
applications. However, it has limitations in terms of maneuverability and
stability. Differential steering works better in open spaces and can struggle
with tight turns or uneven terrains.


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Comment or Message  *


The “Global Status” should become healthy and our two frames should appear,
with a line between them to indicate the transform.


> If you’re not familiar with it, the big numbers starting with “16314……” are
> times, represented in “Unix Time” which is commonly used in Linux systems,
> and so in robotic platforms. For more info on Unix Time (a.k.a Epoch Time)
> check out the [ Epoch Converter ](https://www.epochconverter.com/) . When
> running simulations, Gazebo will generate its own time source, and the
> numbers will be in seconds since Gazebo was started.


#  [ How to transform the whole /tf frame?
](//question2177.rssing.com/chan-36149602/article529-live.html)


    ros2 run robot_state_publisher robot_state_publisher --ros-args -p robot_description:=(something here)

---|---
`


During the design process the two companies' engineering teams worked closely
together to ensure the exacting specifications of the motor package were met.


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Next up, [ we’ll see how to write our own URDF files ](/ready-for-ros-7-urdf/)
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    sudo apt install ros-foxy-xacro ros-foxy-joint-state-publisher-gui

---|---
`


Figuring out all the mathematics and code behind this can be quite tricky, so
ROS provides us with a whole subsystem just to make working with transforms
easier. In this tutorial we’ll learn how to set up a transform tree for some
example cases.


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#  5 Wheeled robot steering mechanisms


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i have a bag file containing a transform tree and want to make a map from
gmapping and hector slam. i want to know what all changes i have to make in
the transforms in order to get the result..


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By addressing the challenges of wheel slippage and sinkage, wheeled robots can
effectively navigate various terrains and environments, enabling their
successful deployment in applications such as search and rescue missions,
agricultural automation, warehouse logistics, and many more.


I am trying to build ros hydro from source on ubuntu 12.04 it requires boost
1.46.1 but the version of boost installed on my machine is 1.48 so I
downloaded boost 1.46.1 and installed it in a local folder. I also added skip-
keys flag in rosdep to stop it from installing boost (because it would remove
the newer version). After installing these dependencies I did
./src/catkin/bin/catkin_make_isolated --install -DCMAKE_BUILD_TYPE=Release as
mentioned here : http://wiki.ros.org/hydro/Installation/Source this started
building plain cmake and catkin packages but gave an error while building tf:
CMakeFiles/tf_monitor.dir/src/tf_monitor.cpp.o: In function `main':
tf_monitor.cpp:(.text.startup+0x3cf): undefined reference to
`boost::thread::start_thread_noexcept()' tf_monitor.cpp:(.text.startup+0x46f):
undefined reference to `boost::thread::join_noexcept()' I specified the boost
library path using CMAKE_LIBRARY_PATH variable cmake is able to find the local
boost installation using this. I also tried changing the CMakeCahe.txt file in
tf package by specifying the location of libboost_thread.so but still no luck
can someone please help .


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The first way is to manually broadcast them using ` static_transform_publisher
` . As you might guess, this tool can’t broadcast dynamic transforms, only
static ones. That might seem a bit useless, but it’s very helpful for learning
transforms, doing quick tests, and acting as the “glue” in a bigger system
(e.g. if two different nodes expect a frame to have different names, or be in
slightly different spots).


This blog explores five commonly used mobile robot steering mechanisms,
including differential drive, Ackermann steering, omni wheels, mecanum wheels,
and skid-steering. We will also delve into different types of wheels commonly
used in wheeled mobile robots, such as omni wheels, castor wheels, and mecanum
wheels. Understanding these steering mechanisms and wheel configurations is
essential for optimizing the performance and capabilities of wheeled mobile
robots, enabling them to navigate efficiently and effectively in a wide range
of applications such as [ mapping ](https://kshitijtiwari.com/all-
resources/mobile-robots/robot-mapping/) , [ localization
](https://kshitijtiwari.com/all-resources/mobile-robots/robot-localization/)
or, [ simultaneous mapping and localization (SLAM)
](https://kshitijtiwari.com/all-resources/mobile-robots/slam-for-beginners/) .


[ 10 Types of robot motors for navigation  ](https://kshitijtiwari.com/all-
resources/mobile-robots/robot-motors/)


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NAVIGATE BY SITE AREA


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ros/tf_screenshot_rviz_add.png)


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December 20, 2014, 9:43 am


In the [ field of mobile robotics ](https://kshitijtiwari.com/all-
resources/mobile-robots/introduction-to-mobile-robotics/) , steering
mechanisms and wheel configurations play a critical role in controlling the
movement and maneuverability of wheeled mobile robots. These robots rely on
various steering mechanisms and [ specialized wheel designs
](https://youtu.be/rP_KmfsfzFg) to navigate diverse environments and perform
specific tasks.


3. Skid-Steering


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April 8, 2024, 1:08 pm


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#  [ Two 6 DOF robots on scene
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Suddenly our job got a whole lot easier! Instead of having to broadcast whole
transforms, all we need to do is publish ` JointState ` messages. Normally,
this data will come from actuator feedback sensors on the robot such as
encoders or potentiometers (and in a simulation environment those can be
simulated). For now, we will just fake the joint states using a tool called `
joint_state_publisher_gui ` . This node will look at the ` /robot_description
` topic published by ` robot_state_publisher ` , find any joints that can be
moved, and display a slider for them. It reads the values from these sliders,
and publishes them to ` /joint_states ` .


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##  Explore  →


**Table of Contents**


#  [ robot_state_publisher design: multiple publishers on /joint_states ok?
](//question2177.rssing.com/chan-36149602/article536-live.html)


* [ LATEST BLOG POST ](/page.asp?obj_id=190807)


As an example, we might want to have a frame ` robot_1 ` that is across and up
from a ` world ` frame, at a 45° (0.785 rad) angle. To do that we’d use the
following command:


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Dear all, If I use robot_localization with [9 Degrees of Freedom - Razor
IMU](https://www.sparkfun.com/products/retired/10736), do I need to provide TF
between base link and imu link? Is TF between base_link and imu_link important
for robot_localization internal processing? Since this IMU uses three
different chips for an accelerometer, gyroscope and magnetometer, which
sensor's location will determine the TF value? Based on this [Q
&A](https://answers.ros.org/question/9957/what-frame_id-to-put-in-a-
sensor_msgsimu-message/), we may need to mount IMU to be aligned with
base_link. In that case, how should I align this IMU due to three separate
chips locations in the PCB?


August 9, 2017, 1:30 pm


which is commonly rectilinear and have limited global localization methods,
aligning the map with building is recommended especially if the building
layout is known apriori. Similarly in an indoor environment it is recommended
to align the map at floor level. In the case that you are operating on
multiple floors it may make sense to have multiple coordinate frames, one for
each floor.
If there is ambiguity fall back to the conventions for unstructured
environments above. Or if there is limited prior knowledge of the environment
the unstructured conventions can still be used in structured environments.
###  earth
The coordinate frame called ` earth ` is the origin of ECEF.  [2]
This frame is designed to allow the interaction of multiple robots in
different map frames. If the application only needs one map the ` earth `
coordinate frame is not expected to be present. In the case of running with
multiple maps simultaneously the ` map ` and ` odom ` and ` base_link ` frames
will need to be customized for each robot. If running multiple robots and
bridging data between them, the transform frame_ids can remain standard on
each robot if the other robots' frame_ids are rewritten.
If the ` map ` frame is globally referenced the publisher from ` earth ` to `
map ` can be a static transform publisher. Otherwise the ` earth ` to ` map `
transform will usually need to be computed by taking the estimate of the
current global position and subtracting the current estimated pose in the map
to get the estimated pose of the origin of the map.
In case the ` map ` frame's absolute positon is unknown at the time of
startup, it can remain detached until such time that the global position
estimation can be adaquately evaluated. This will operate in the same way that
a robot can operate in the ` odom ` frame before localization in the ` map `
frame is initialized.
Earth Centered Earth Fixed diagram
A visualization of Earth Centered Earth Fixed with a tangential ` map ` frame.
##  Relationship between Frames
We have chosen a tree representation to attach all coordinate frames in a
robot system to each other. Therefore each coordinate frame has one parent
coordinate frame, and any number of child coordinate frames. The frames
described in this REP are attached as follows:
%% Example diagram graph LR O(odom) --> B(base_link) M(map) --> O E(earth) -->
M
The ` map ` frame is the parent of ` odom ` , and ` odom ` is the parent of `
base_link ` . Although intuition would say that both ` map ` and ` odom `
should be attached to ` base_link ` , this is not allowed because each frame


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When a node broadcasts a particular transform, it can either be _static_
(doesn’t change over time), or _dynamic_ (may change over time, but doesn’t
have to). The reason for this distinction is that robust systems will need to
know if their information is out of date, and can flag an error if the
broadcaster hasn’t updated a dynamic transform for some time. Static
transforms, on the other hand, can be broadcast once and are assumed to be
correct until a new one is broadcast.


Kshitij Tiwari is a Freelance Robotics Consultant, Career Mentor and Educator
for early stage researchers. He obtained his Ph.D. from JAIST, Japan (2018),
MSc from University of Edinburgh (2014) and BEngg from University of Hong Kong
(2013).


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May 21, 2014, 1:49 am


> Note, For the case of a mobile platform, things will get a bit more
> complicated. ` robot_state_publisher ` can broadcast all the transforms
> within the robot, but you’ll need other nodes to publish transforms such as
> the robot’s location within the environment. There are existing nodes to
> handle this kind of thing, but they’ll be covered in later tutorials.


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August 15, 2017, 10:54 am


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