How to get the point's position in PTAM?

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Hello! It is the first time for me to learn ros and ptam,so I am not familiar with them. Now I want to know whether we can get the point's position in PTAM. I have learned the node information and tried to use the topics and services, I just find topic which can help to get the information of the camera, but I didn't find any topic or service to give the point's position. If there is some topic or service or other things which will help, please tell me. Any information will be appreciated. Thank you!