One of the Lehmann's rules of plane tabling, is

• location of the instrument station is always distant from each of the three rays from the known points in proportion to their distances
• when looking in the direction of each of the given points, the instrument station will be on the right side of one and left side of the other ray
• when the instrument station is outside the circumscribing circle its location is always on the opposite side of the ray to the most distant point as the inter-section of the other two rays
• none of these.