1. Digitize vessel as an open entity (do not close to make a polygon).

2. Draw midline based on vessel diameter.

Set COORDS to 2, to measure distance from rim (radius) and angle (180); and use F8 (ORTHO) to have straight lines.

PLINE: start on point 1; move left watching coordinates (lower left), and click on point 2 when yo see 5<180 (if radius=5); then start a prependicular line down to draw the midline and stop in point 3.

3. TRIM overshots of profile and line.

Continue to step 2