Patent ID: 6904697

Claim:
A method of approximately field marking an arc of a circle having an obstructed center, the method comprising: identifying an eccentric ellipse that will substantially overlap the arc, the ellipse having a first focus and a second focus, both of which are field accessible and unobstructed; securing a first point of a first line indicating means at or near the first focus; securing a second point of the first line indicating means at or near the second focus while pulling the first line indicating means tight between the first and second points; securing a first point of a second line indicating means at or near the first focus; identifying a second point of the second line indicating means, wherein the second point is located a distance from the first point of the second line indicating means equal to the length of the major axis length of the ellipse; securing the second point of the second line indicating means at or near the second focus; pulling the second line indicating means tight between the first and second points of the second line indicating means in order to mark out where the ellipse substantially overlaps the arc; and using a marking instrument to mark out a plurality of points of the ellipse wherein the ellipse substantially overlaps the arc.