About COGO descriptions

This topic applies to ArcEditor and ArcInfo only.

The geometry of a straight line can be described using a direction and a distance. Similarly, you can describe the geometry of a circular arc with parameters such as arc length, chord distance, radius, central angle, and tangent length.

Parameters describing a line
Parameters describing a circular arc

COGO lines

A COGO line is a feature that is either completely straight or completely circular. If the feature has any vertices between the endpoints, every vertex must fall within the x,y tolerance of a line or curve created between the endpoints. Only these types of line features have valid COGO descriptions.

The lines on the left are COGO lines, the ones on the right are not.

COGO lines can be created a number of ways. For example, you can create them when you use the following:

Required COGO fields

The table below lists and describes the required table fields to maintain COGO attributes.

Field name


Field alias


Direction (or Angle)

If the feature is straight, this is the direction of the line. If the feature is a circular arc, this is the direction of the chord line. The field is named either Angle (to be compatible with ARC/INFO coverages) or Direction (if you use the Create COGO Fields command).

COGO Direction

Text Length=12


If the feature is straight, this is the distance between the endpoints. If the feature is a circular arc, this is the distance along the chord line.

COGO Distance

Text Length=10


The central angle formed between the endpoints of the curve and the center point. When editing in ArcMap, this is typically referred to as the Angle.

COGO Delta

Text Length=10


The length from the center point to the curve.

COGO Radius

Text Length=10


The distance between the endpoint and the point of tangency. The point of tangency is determined by intersecting a perpendicular line from each of the endpoints of the curve.

COGO Tangent

Text Length=10


The length along the curve. When editing in ArcMap, this is typically referred to as Arc.

COGO ArcLength

Text Length=10


The side on which the center point of the circular arc is located.


Text Length=1

Outputting COGO descriptions

Specific COGO commands in ArcGIS can store the COGO descriptions you enter as attributes on COGO line features. The values added include the direction and length for straight features and curve characteristics such as chord distance, chord direction, arc length, radius, tangent length, and side. The current direction type and angular units for the ArcMap editing environment are used when populating these attributes. The map's current coordinate system linear units are used when populating distance attributes.

The COGO commands in ArcGIS should be used to update line features to maintain COGO attributes. For example, to split a line, use the Proportion tool on the COGO toolbar so the COGO attributes will be automatically updated. Using the Split command or tool will not update COGO attributes.

The following commands write COGO descriptions to the COGO attributes of a line feature class:

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