A computer-assisted medical system comprising: a computer-assisted medical device comprising an articulated arm , the articulated arm configured to have a distally mounted instrument , wherein the distally mounted instrument is configured to be inserted at a body opening into a patient on a surgical table; and a control unit coupled to the articulated arm ; wherein the control unit is configured to: determine a first motion of the surgical table based on information received from the surgical table , the surgical table being coupled to the control unit via a communications connection, the first motion of the surgical table causing a corresponding second motion of a control point of the articulated arm due to movement of a portion of an anatomy of the patient, the portion of the anatomy corresponding to the control point when the instrument is inserted at the body opening; characterized in that the control unit is further configured to: determine a first angular direction of a horizontal component of the first motion relative to an axis in a surgical table coordinate frame; determine a second angular direction of the second motion relative to an axis in a computer-assisted medical device coordinate frame; and determine a third angular relationship between the surgical table coordinate frame and the computer-assisted medical device coordinate frame based on a difference between the first and second angular directions. a computer-assisted medical device comprising an articulated arm , the articulated arm configured to have a distally mounted instrument , wherein the distally mounted instrument is configured to be inserted at a body opening into a patient on a surgical table; and a control unit coupled to the articulated arm ; wherein the control unit is configured to: determine a first motion of the surgical table based on information received from the surgical table , the surgical table being coupled to the control unit via a communications connection, the first motion of the surgical table causing a corresponding second motion of a control point of the articulated arm due to movement of a portion of an anatomy of the patient, the portion of the anatomy corresponding to the control point when the instrument is inserted at the body opening; characterized in that the control unit is further configured to: determine a first angular direction of a horizontal component of the first motion relative to an axis in a surgical table coordinate frame; determine a second angular direction of the second motion relative to an axis in a computer-assisted medical device coordinate frame; and determine a third angular relationship between the surgical table coordinate frame and the computer-assisted medical device coordinate frame based on a difference between the first and second angular directions. determine a first angular direction of a horizontal component of the first motion relative to an axis in a surgical table coordinate frame; determine a second angular direction of the second motion relative to an axis in a computer-assisted medical device coordinate frame; and determine a third angular relationship between the surgical table coordinate frame and the computer-assisted medical device coordinate frame based on a difference between the first and second angular directions. <EOS>