COGO-Finding the Chord, Radial or Tangent Direction for a non-tangent curve

StephenRock1 — Fri, 03 Mar 2017 20:53:04 GMT

Hello, I am trying to use COGO to create a parcel boundary of a property from a tax map and am having trouble adding a non-tangent curve segment since the tax map does not have the chord direction for the curve. I have the radius, arc length, angle, and tangent length. The curve calculator in COGO doesn't seem to give the chord, radial or tangent directions. The tax parcel is rather large so the only option I see currently is to reverse the order I am traversing to get to the curve segment from the other end. Is there an easier way? I'm sharing a screenshot of the curve in question, I've outlined it. Thanks in advance.

Re: COGO-Finding the Chord, Radial or Tangent Direction for a non-tangent curve

NathanFreitas — Wed, 07 Jun 2017 17:28:24 GMT

Based on the image you shared it would seem that the segment with the bearing of N 19-29-58 W is tangent to the curve in question.

1. The radial bearing from this tangent line is simply a perpendicular bearing (90 degrees) - N 70-30-2 E

180+ N 70-30-2 E = S 70-30-2 W (you need the bearings to point away from the radius point for this calculation)

S 70-30-2 W + Angle 11-1-51 ( add because the curve approaches the West axis or S 90 W).

The radial bearing you want will be the opposite direction of the previous calculation or

S 81-31-53-W + 180 = N 81-31-53 E (Radial Bearing)

2. The Chord bearing can be calculated by taking half the delta which is approximately 5-30-55.5 and the (radial bearing + 180) = S 70-30-2 W then add the 2 together to get S 76-0-57 W this is the radial bearing of the midpoint of the curve. The chord bearing is perpendicular (90 degrees) to this bearing which my math tells me is N 13-59-3 W.

Personally I would use the radial bearing because it does not approximate like the Chord Bearing calculation does with the half angle.

These figures only work if one of the lines approaching the curve is tangential.

I have not found a way to calculate any bearings if both segments approaching the curve are non tangential.

I am open to suggestions if anyone knows how to that.

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COGO-Finding the Chord, Radial or Tangent Direction for a non-tangent curve

Re: COGO-Finding the Chord, Radial or Tangent Direction for a non-tangent curve