find 3D location of the sensor when a depth image arrives

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Hey buddies! I went through the forum and couldn't find a satisfying answer. Sorry, if I reopened an already-answered question.

Basically, I need to write a ROS node that will print the 3D location of the sensor and the timestamp in a text format when it detects a depth image.

Here is what I think I should do (tho I don't know how to):

1. Build a robot with odometer and mount a web camera on it.
2. Create a node that will publish odometer's data. ->odom_node
3. Create a node that will detect 3D images. -> cam_node
4. I somehow will make the odom_node to listen to the cam_node.

I have thousands of questions to ask but that would make it too broad, I don't really know where to start. Could someone direct me to some good tutorials and projects where I can learn and finish the project on my own?

I appreciate all the answers. Thank you in advance.