How do you deal with mismatched directions in COGO traverse? Example provided.

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04-13-2023 05:53 AM
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HenryUnderwood1
New Contributor III

I'm confused about how to enter in a traverse in ArcGIS Pro. I'm used to keying in bearings and distances going around a parcel (but not curves). My experience is that plans mailing go around it in one direction (clockwise or counterclockwise). In the example below, it is indicated as mainly clockwise but there is a curve thrown in that goes the other way.

In the example below, you see NE bearings but then there is a SW for the curve. When I key it in, the curve goes the wrong way (see below). 

HenryUnderwood1_1-1681389839698.jpeg

Here it is as entered. The curve goes the wrong direction.

HenryUnderwood1_0-1681389730935.png

If I tell it to go NE, the curve doesn't match the plan.

HenryUnderwood1_2-1681390367586.png

Can someone correct my understanding of how to do this? Or do you see what is going wrong?

 

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jcarlson
MVP Esteemed Contributor

Curving to the left requires a negative radius value.

Edit to add: when we get plats that don't follow the "one-way" convention, I will just flip the bearings by 180 during entry to get the traverse to close, then go in afterward and flip the specific lines to match the plat.

- Josh Carlson
Kendall County GIS

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jcarlson
MVP Esteemed Contributor

Curving to the left requires a negative radius value.

Edit to add: when we get plats that don't follow the "one-way" convention, I will just flip the bearings by 180 during entry to get the traverse to close, then go in afterward and flip the specific lines to match the plat.

- Josh Carlson
Kendall County GIS
HenryUnderwood1
New Contributor III

Thanks for the help!

When you say flip the bearings by 180, can this be done in this case by Changing S 17-46-37 W to N 17-46-37 E? Is there another quick way to do this in the traverse window?

Am I right that the notation on the plan "R" is radius and "C LEN" is chord length? I wasn't able to find a document that explained these abbreviations.

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jcarlson
MVP Esteemed Contributor

For your first question, yes. A quicker way is to use the quadrant shorthand:

  1. NE
  2. SE
  3. SW
  4. NW

So the bearing S 17-46-37 W can be represented by 17-46-37-3. Note that the Traverse tool (or really anywhere you'd enter a bearing, like in the attribute panel, etc) will look at the last number after a "-" for a quadrant, so if your bearing had no minutes or seconds, you can omit them. The bearing N 45-00-00 W can be entered as 45-4.

In that way, you're just flipping the last digit, so 1 <-> 3, 2 <-> 4.

And yes, those abbreviations sound right. The way plats are written tend to follow a regional standard or convention. For instance, most plats I get do not give chord lengths, and unless otherwise stated, all curves are assumed tangent to the preceding segment, so often there's not even a bearing given on curves.

By the way, check out the "data entry shortcuts" section of the documentation: https://pro.arcgis.com/en/pro-app/latest/help/editing/enter-a-traverse.htm#GUID-5B9D1444-2C4D-4571-9...

You'll find there are many handy ways to enter different values. In the event that I do get a chord bearing, I can enter 17-46-37-1 cb and the tool will know to treat that value differently.

- Josh Carlson
Kendall County GIS