Abstract: A method performed by a computing system comprises determining an entry position and entry vector of an entry port in a surgical coordinate space. The entry port provides a passageway for insertion of a first medical instrument into a patient's body. The determination of the entry position and entry vector occurs while the first medical instrument is external to the entry port. The method also comprises positioning the first medical instrument based on the entry position and the entry vector of the entry port and advancing a distal end of the first medical instrument along the entry vector into the entry port.