Can somebody shed some light regarding how to draw a spiral curve listed in a legal description? I am using AutoCad Civil 3d 2016.


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Hi Mason.

There are , I think 3 videos on transition curves parts 1-3 here at LSU I do not think they go over AutoCad 

But maybe some of it, there is a lot of info on the web for autocad. The thing is under standing spiral curves,and all of it parts. Which that you may not need. I have always like solving them long handed

with equation ,then checking it with a program. But I like math ,just for fun. But see if this can help.

I don't have a clue about autocad since I have never used it. I was using CAD long before anybody ever heard of Bill Gates or Windows & found autocad over priced & not cost effective. Assuming the curve data is mathematically sound, drawing it should not be a problem in any decent cad program. Any of the up to date co - go programs that run inside of autocad should be able to handle the task as well. Most of it doesn't float my boat but there is survey software out there that will do anything, maybe even drive the truck. If I couldn't draw any curve in my surveying program, I would be looking for different software.

Most lawyers here don't even attempt to write legal descriptions anymore & definitely not anything as complicated as a spiral curve. They generally just reference the plat. That way at least they get something right. The last legal description I had to deal with calculated two acres but the deed conveyed one acre. Oh yea!, the County name was also spelled incorrectly. They just copy the previous description, errors & all & it is rare that anything is updated. Why are lawyers allowed to write legal descriptions?

Then there was the case where the lawyer got me to survey & record a new plat to change a property line because the existing property line ran through a portion of the house. Then he conveyed the property by the old plat so the property line still ran through the house!

Many Australian states continue to use curve boundaries for legal descriptions to define physical boundaries on the ground such as canal walls. It is not generally used where it is intended to fence the boundary. A legal description of the boundary is to define the tangent points, provide a traverse connection across the cord and finally a fixed radius. Complicated spirals or the like are not used as they are too difficult to explain to non surveying people. The spirals are broken down to individual curves. This document is very helpful.
Set points on spiral; then use auto cad spline function to draw the spiral. It's like drawing contours between known elevation points

I'm still using autocad with LDD3 (Land development desktop)  There is a command that will automatically draw the spiral.

Realize that there's really no such thing as an offset and parallel spiral.  You can get close, but no cigar.

I'm not sure how your legal description is worded, but there's a SPIRAL command in C3D that seems to give you good control of the outcome.


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