# How is the coordinate system working in URDF I am a beginner and I can't seem to understand as I was going through some examples of URDF that how the Coordinate system is working here though, I am sure it's working normally but it's not making any sense to me. Below is an example.

<?xml version="1.0">
<robot name = "my_first">

<visual>
<geometry>
</geometry>
<origin rpy = "0 0 0" xyz = "0 0 0"/>
<material name = "yellow">
<color rgba= "1 1 0 1"/>
<material/>
</visual>

<joint name = "pan_joint" type = "revolute">
<origin xyz = "0 0 0.1"/>
<axis xyz = "0 0 1"/>
<joint/>

<visual>
<geometry>
<cylinder length = "0.4" radius = "0.04"/>
<geometry/>
<origin rpy = " 0 0 0" xyz = " 0 0 0.09"/>
<material name="red">
<color rgba="0 0 1 1"/>
<material/>
<visual/>

<joint name="tilt_joint" type="revolute">
<origin xyz="0 0 0.2"/>
<axis xyz="0 1 0" />
</joint>

<visual>
<geometry>
</geometry>
<origin rpy="0 1.5 0" xyz="0 0 0"/>
<material name="green">
<color rgba="1 0 0 1"/>
</material>
</visual>
</robot>


How are the Pan_link's and tilt's xyz is calculated ? Whats the differnce b/w origin rpy and xyz ? please help me out here

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Sort by » oldest newest most voted http://wiki.ros.org/urdf/XML/model ,
http://wiki.ros.org/urdf/XML/joint ,

joints represent connections between link / reference frames:

• origin rpy attribute: "Represents the rotation around fixed axis: first roll around x, then pitch around y and finally yaw around z. All angles are specified in radians" (Tait-Bryan xyz extrinsic rotations) relative to the parent link's reference frame (effectively the parent joint).

• origin xyz attribute: Represents the x, y, z translation relative to the parent link's reference frame (effectively the parent joint).

• origin rpy attribute: "Represents the rotation around fixed axis: first roll around x, then pitch around y and finally yaw around z. All angles are specified in radians" (Tait-Bryan xyz extrinsic rotations) relative to the parent joint.

• origin xyz attribute: Represents the x, y, z translation relative to the parent joint.

If you want to be confused: https://en.wikipedia.org/wiki/Euler_a...

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thanks a lot, I did not the read the above links, I will read it and see it though.

That video helped me when I started learning about urdf/ros!