# Inputting legal description into ArcMap using COGO tool

I have a legal description that I need to create in ArcMap, and I'm not certain how to input some of the descriptions.

Here are a couple of the descriptions I need to input:

If I only input the part that states:

"...the chord of which bears North 47° 52' 22" West 88.90 feet to a point of reverse curve"

From each section and leave out:

"...thence 90.89 feet along the arc of a 125.00 radius curve to the left"

Then it roughly follows the correct path with a straight line, but it should be slightly curved.

I believe each section is describing a single curved line, but there are 4 parameters, and with the COGO tool, the most I can enter for a curve is three!

So, for the underlined blue and green descriptions in the above image, if I enter these, then it does create straight line segments that roughly follow the path:

Blue:

Green:

But how do I add the

"...thence 90.89 feet along the arc of a 125.00 radius curve to the left"

So that it creates the curved line?

• Chord Lenght, Central Angle, Arc Lenght and Radius are not independent (two of them can be calculated from the other two). You need the Chord Direction and two any of the other variables to correctly define a curve. Commented Nov 25, 2019 at 16:24
• My answer could possibly be shorter and more conclusive if you gave us rather more contextual data for your parcel and its curves. Commented Nov 27, 2019 at 19:46

According to desktop.arcgis.com/en/arcmap/10.3/manage-data/editing-parcels/tangent-curve.htm you can enter curves via the Tangent Curve dialog.

The following assumes that you do have tangent data available. For each curve, you need the direction of the tangent to the curve, the arc length, the curve radius, and L/R (left or right). You would actually ignore both chord parameters (its direction and length).

Typically, the curve's tangent is the direction of the previous straight segment. For now, let's assume that's the case in your parcel: The two legal description snippets you show both cut off the previous course data so we cannot say exactly what to enter for them, but the radius and arc length would be `125.0 56.38 L` and `125.0 90.89 L` for your 'blue' and 'green' curves, respectively.

There are many different parameters that can be used to describe a curve and different land survey regulations follow different conventions. Your example curve descriptions show redundant data and, if you prefer, you could choose different parameters to enter after making another selection from the Circular Curve Parameters drop-down.

If a curve is not tangent to its previous line segment, you may have to infer the tangent's direction from other legal description data, if available. It looks like you may be able to do this via the Curve Calculator tool.

Thanks to a link given by Gabriel, it looks like you can enter non-tangential curves -- see desktop.arcgis.com/en/arcmap/10.3/manage-data/creating-new-features/about-creating-a-line-with-the-traverse-window.htm. In your case, you would use the Chord Direction option, as that's what you have.

If you cannot determine the tangent's direction from any other data or tool, it looks like you cannot use ArcGIS in this case. (I'm no expert, so someone else may have to chime in.) There are other tools out there that do allow entry of non-tangent curves. One such tool is Copan for Windows. It's completely free.

• There are not a few cases, in which the description of a curved segment of a plot does not imply that it is tangential to the previous or the next segment: i.sstatic.net/GoyBF.jpg Commented Nov 27, 2019 at 5:14
• @GabrielDeLuca - Good point. I added further notes/conditions/advice about tangency. Commented Nov 27, 2019 at 19:44
• From the following documentation site: desktop.arcgis.com/en/arcmap/10.3/manage-data/…, I understand that it is necessary to create a Curve Course from the Traverse window, set the Choord Direction as the direction of the curve, and any two of the other parameters. It does not look complicated to adjust the requirements to the data provided in the question. But I don't have an ArcMap license, so I'm not in a position to write an answer. Commented Nov 27, 2019 at 22:27
• @MartinF thanks, I just saw your reply. I will test ASAP and respond. Commented Dec 3, 2019 at 22:48