How can we approximate tangent spiral curves?

Question

Hello,

We need to draw tangent spiral curves in our parcel fabric.  However, it appears that the parcel fabric at least at ArcGIS 10.3 does not allow us to draw tangent spiral curves.  In the meantime:

* How would be begin to approximate tangent spiral curves?
* Is there a tool out there that will calculate the beginning and ending XY coordinates of a tangent spiral curve?   That way we can at least draw the rest of the parcel accurately and then come back to the curve once ESRI allows us to draw tangent spiral curves.

Thanks

JeffWard · Answer

There was a post a few years ago about spiral curves and Tim Hodson​ replied asking how much interest there would be in Esri providing this capability.  Apparently there wasn't enough interest at the time.  From what I read on that post some folks are just using the chord in place of the spiral curve.  But to do that you would still need to be able to calculate where the spiral ends.  I bought a couple of the ebooks at this site and I am able to calculate the endpoint of the spiral using the formulas, but not quickly or easily.

What would be nice is if there were a tool that would calculate the chord bearing and the chord length of the spiral curve at least until Esri can get the capability into the traverse grid.