Surface profile between sections on a curved surface

[[Ki...]]

Hi, 

I have been tasked with measuring a surface profile on a coned part. The patch I can select includes more surface than needed. I have attempted to use the deselection in 3D tools with no luck. 

The surface area is essentially where the black point is. The image shown is a section through the cone. The surface profile is on a quarter of the cone AND between two other sections. 

 

Any ideas on how to approach this? 
Thanks