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How do you describe a curve?

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Mark R
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Curve to the right or left covers it. Once we add concavity, or convexity, it gets confusing to some, and don't we emulate the attorneys we all despise? Keep it simple and clear. No weasel words.


 
Posted : May 18, 2012 9:57 pm
dave-karoly
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I had a co-worker years ago, his birthday was one day after mine.

He got to call me "old man" for one day every year.


 
Posted : May 18, 2012 9:59 pm
Brad Foster
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> I thought radius and chord bearing and distance was a Sacramento County oddity that you don't see elsewhere.
>
> Maybe Joe Spink (a very busy CE from the 1930s to 1960s) brought it from Oregon.

That is also standard in Hawaii. However, if the curve is a tangent curve (and most are) I prefer to calc through the radius point instead of using the chord distance, (which is actually a calculated number).

For example, in a simple subdivision with rectangular lots, the M & B description would describe a 20' radius curve to accommodate a street intersection with the chord azimuth, and the distance as 28.28 feet. But the distance is actually 28.28427... feet. This way, it takes some of the slop out of the calculations.


 
Posted : May 18, 2012 10:20 pm
squinty-vernier
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> Thence with the arc of a tangent curve to the right having a radius of 160.00 feet and a central angle of 33 degrees 17 minutes 28 seconds, an arc distance of 92.97 feet to a point of tangency;
>
> more or less.

+1

Non-tangent curves (they show up from time to time), or narratives that intersect a curve, have the radial bearing added.

Rick


 
Posted : May 19, 2012 4:53 am
Neil Shultz
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I am not really sure. That is the info my grandfather always put on his plats. I think it may be that when he shot the curves in the field, he calculated them from the tangent. We always shot a PC, PT, and a few POC's on the road. My prefered method is to calculate a best fit radius based on an external and a delta to lay out the curves. Note, these are "undesigned" curves in the road in SWPA where nothing is straight for much more than 200'


 
Posted : May 19, 2012 7:16 am

GigHarborSurveyor
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Thence North 56°13'49" East, ###.## feet to the beginning of a 160.00 foot radius curve to the right;
Thence along said curve an arclength of 92.97 feet;
Thence North 89°31'17" East, ###.## feet...

If it were a non tangent curve then ...to the beginning of a 160 foot radius non-tangent curve with a radial bearing of South 33°46'11" East

On plans I always show the Delta, but I do not put it in my descriptions. I do like having the Delta when drafting up the descriptions though since the cad program I use works smoothest using it.

There are no requirements here that certain elements are required in descriptions. In fact, there is no requirement that they be prepared by a Surveyor (except within some ordinances pertaining to municipally approved adjustments or subdivisions), though many of us would like to see suck a law.


 
Posted : May 19, 2012 9:08 am
spledeus
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i would rather have the radial bearings and the radius than any other piece of data

i am sure to add radial bearing for all compound curves, but if the curve is tangent to two straight lines, i see no need to add more data. i will hold the two straight lines over the length and radius all day long.


 
Posted : May 20, 2012 7:31 pm
Kris Morgan
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>
>
> Given the information from the sketch, or whatever else you please, describe the curve from tangent in to tangent out in your format of choice.

THENCE Northeasterly along a curve to the right having a delta of 33°17'28", a radius of 160.00 feet, an arc length of 92.97 feet, and a long chord of North 72°52'33" East, 91.66 feet to a point for the end of said curve.


 
Posted : May 21, 2012 7:34 am
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