Central Angle Curves??

[Anonymous User]

I'm attempting to complete this legal description below and not sure how to go about utilizing the Traverse tool to complete these central angle curves?

[jcarlson · Accepted solution]

The description is giving you a lot of details about these curves, but I am not sure you need to use all of them.

To take one of them as an example, look at:

A NON-TANGENT CURVE CONCAVE TO THE NORTHEAST
HAVING A RADIUS OF 2325 FEET
THE LONG CORD OF SAID CURVE BEARS NORTH 72-00-38 WEST 1737.58 FEET
THENSE NORTHWESTERLY 1780.79 FEET ALONG THE ARC OF SAID CURVE
AND ALONG SAID SOUTHERLY BOUNDARY THROUGH A CENTRAL ANGLE OF 43-53-05

What you've got here are

1. The radius: 2325
2. The chord bearing: N 72-00-38 W
3. The chord length: 1737.58
4. The arc length: 1780.79
5. The delta angle: 43-53-05

All you need in your Traverse are a few of these, and your curve can map properly. I prefer arc length and chord bearing when I have them. In the Traverse table, you'd enter the following:

Bearing	Distance	Radius	Arc Length
72-00-38-4 cb		2325	1780.79

You can click on the column headers in the traverse tool to change what kinds of values it's looking for. For instance, you could change the Arc Length column to look for Delta Angle instead, and enter the delta angle values. You can configure whether or not it assumes tangent bearing or chord bearing, too. (Putting "cb" after a bearing overrides the default and tells the traverse to treat it as a chord bearing instead).

[Anonymous User]

Thank you. What does the -4 before cb indicate?

[jcarlson]

That's quadrant bearing shorthand. 

1 = NE

2 = SE

3 = SW

4 = NW

When you're entering data into a field in Quadrant Bearing format, Pro can interpret a variety of entries. As long as the final character is a single digit from 1 to 4, it will assume you are referring to a quadrant.

These aren't real angles, but here's an illustration:

[Anonymous User]

Excellent! One more favor. Can you provide examples for next 2 curves in that legal. I would like a few examples to reference if possible. I really appreciate your time on this. You've been a HUGE help.

[jcarlson]

Sure thing!

First Curve

This one seems a bit incomplete, but we can see that because it says "continuing", this call will be tangent to the previous and will use the same radius. The traverse will automatically populate the exit bearing of the preceding call, but you can also put in "*" to make it tangent, too.

"1318.11 feet along the arc" --> arc length

Second Curve

This is a "non-tangent curve", so we'll need a bearing.

"the long chord...  --> chord bearing

"42.19 along the arc" --> arc length

"radius of 25 feet"

The Traverse Table

Direction	Distance	Radius	Arc Length
*		2325	1318.11
65-55-58-2 cb		25	42.19