Coordinate Geometry (COGO) is used to measure and locate features such as land parcels, road centerlines, and utility easements. COGO measurements typically describe features relative to each other and are recorded on survey plans, deed descriptions, and other types of physical or electronic land record documents.
Survey plans can include references to points with known coordinates that spatially locate or georeference COGO features within a coordinate system. These points are known as control points, monuments, or cadastral reference points.
In ArcGIS Pro, COGO descriptions comprise a set of measurements that define a line feature. Straight lines are described with a direction and a distance. Curved lines include a radius, angle, arc length, and chord direction.
Spirals are described with two radii. The second radius can be set to infinity. Spirals describe transitions to and from circular curves or straight tangents, for example, to record the designed alignment for a roadway or railroad.
The following example survey plan shows a road centerline and parcel boundaries adjoining the road drawn as lines with COGO measurements.
Ground to grid correction
Ground to grid correction is a drawing mode that converts COGO ground measurements to grid measurements defined by the coordinate system of your feature data. Ground to grid correction is applied automatically when you turn ground to grid on and use ground to grid aware tools.
It is common for ground measurements on a survey plan to be different than grid measurements. Setting accurate grid correction values ensures that feature geometry is correctly rotated and scaled for a specific plane coordinate system.
Ground to grid settings are available on the Edit tab, in the Correction group.
Projection on the fly
When you edit a feature in a projected coordinate system, all edits occur in the map coordinate space. If the feature layer source data is in a different coordinate system, this is referred to as projection on the fly.
For most editing operations and most coordinate system transformations, the integrity and accuracy of the feature is maintained. However, certain editing operations may produce unexpected alignment or accuracy errors, depending on the coordinate systems being used.
To get the best results in these situations, change the coordinate system used by the map to match the coordinate system of the layer or layers you are editing.
COGO feature types and usage
You can use simple point, line, and polygon features to represent COGO features or use a parcel fabric to manage, edit, and share parcel data in single-user and multi-user environments.
COGO can be used for the following features:
- Points that represent the endpoints of measured lines and curves. Points can also represent surveyed points and have known x,y,z coordinates. You can use a simple point feature class with x, y, z attributes to represent these points, or use a parcel fabric to manage parcel points.
- Lines that represent measured distances and directions. Measured lines can also represent curves and spiral curves. You can use a simple line feature class or manage parcel lines in a parcel fabric. COGO lines can be created with the 2-point line tool, the Circular Arc tool, or the Traverse tool.
- Polygons that represent parcel areas enclosed by COGO lines. You can use a simple polygon feature class or manage parcel polygons in a parcel fabric. Polygon features can be created with the Construct Polygon tool by starting from selected COGO lines. Polygons can also be created using the Traverse tool.
COGO-enabled line features
COGO-enabled line features contain additional attribute fields for storing COGO measurements independent of the geometry attributes. Features draw with COGO symbology and include a label expression that labels each line with its COGO dimension, when it exists.
To add or remove COGO fields, use the following geoprocessing tools:
| Tool | Description |
|---|---|
Enables COGO on a line feature class and adds COGO fields and COGO-enabled labeling to a line feature class. | |
Disables COGO on a line feature class and removes COGO fields and COGO-enabled labeling and symbology. |
COGO-aware editing tools
When a line feature class is COGO enabled, COGO-aware editing tools preserve, calculate, and proportion existing values in COGO fields. Similarly, dynamic constraints and tools that specify direction and distance update COGO fields.
When you create geometry, tools that appear on the construction toolbar are Ground to Grid aware. These tools include the segment construction tools and the intersection tools.
The COGO-aware tools listed in the following table are available in the Create Features pane.
| Tool | Description |
|---|---|
Creates two-point single-part line features. The sketch is automatically finished when you create the second vertex. | |
Creates two-point tangent arc segments based on your specified parameters. Note:To access this tool, right-click the map while sketching a feature. | |
Creates clothoid spiral curves based on your specified parameters. Note:To access this tool, right-click the map while sketching a feature. |
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The COGO-aware tools listed in the following table are available in the Modify Features pane:
| Tool | Description |
|---|---|
Creates a series of line features or a single polygon feature by typing values. This tool supports single-handed data entry using the numeric keypad. | |
Updates the direction and distance attributes of a COGO-enabled line feature to match the selected feature geometry. When ground to grid is turned on, the calculated values are rotated and scaled by the current correction settings. | |
Creates cul-de-sac geometry that is aligned with a selected line feature representing the centerline of a road. | |
Creates two-point COGO lines and arcs from selected line features. The feature is split at each vertex. | |
Extends or trims a line feature to an existing feature boundary. | |
Creates a tangent circular arc between two segments by reshaping the first segment and trimming the second segment. | |
Splits straight and curved line features at intersections or inferred intersections. You can extend a line to an inferred intersection or create a segment. | |
Splits editable and visible features into two or more features. You can draw a line to create the split or select input cutting features and split only selected target features. | |
Contains methods for dividing a single-part polyline feature into multiple features that have equal or varying distances, or a percentage of the total length. | |
Copies line features parallel or concentric to existing line features at a specified offset distance. | |
Creates features at specified distances along a line at a specified perpendicular offset from the line. |
