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An overview of COGO

Release 9.3
Last modified November 10, 2008
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When surveyors or civil engineers need to record the location of human-made features, such as land parcels, road centerlines, utility easements containing transmission lines, oil and gas leases, and so on, they typically provide the results on a survey plan that describes the location of features relative to each other. Below is an example survey plan that diagrammatically shows a road centerline and the edge of the land properties adjoining the road. The road centerline and parcel boundaries comprise a number of straight and curved lines.

Example COGO survey plan

Each line has measurements that describe it. A straight line has a direction and distance, while a curved line has a radius, angle, arc length, direction, and so on. These measurements are coordinate geometry (COGO) descriptions. You can use these COGO descriptions to accurately re-create the features the surveyor captured. The survey plan also includes references to existing locations that help you to tie these new features into your GIS database. The reference could be the coordinates for a point or a measurement to a well known location such as a control point, a road intersection, or an existing parcel corner.

Building blocks for COGO

The basic building blocks for COGO are:

Creating features from COGO descriptions

The commands and dialog boxes in the ArcMap editing environment for creating features from COGO descriptions are integrated into the editing experience. The common commands and dialog boxes you will use include:

These are just some of the commands and dialog boxes available for creating features in ArcGIS. Refer to Common COGO workflows to understand how you can use these and other commands to build and maintain your land parcels.
When you are creating features, you still need to set the target layer so ArcMap knows which layer you want to update. For the Traverse and Offset Line windows, you also need to set the edit task to either Create New Feature or Create 2-Point Line Features.

Correcting for differences between the survey plan and GIS data

When you are using the COGO descriptions from a survey plan, you are using measurements the surveyor took on the ground and possibly adjusted to some coordinate system. However, a GIS stores coordinates relative to a projections coordinate grid. You can use the ground to grid correction to adjust the geometry of the features you create.

Reporting COGO descriptions

Before you begin adding features from COGO descriptions, you may need to investigate and understand how the new features will fit compared to the existing features. You can use the COGO Report dialog box to measure directions and distances between points you click on the map as well as query the COGO descriptions for line feature in your database. You can also use the COGO Area command to calculate the legal area of selected line features, useful when deciding which approach to use when modifying features.

Storing COGO attributes on line features

In ArcMap, you can store the COGO values that you enter when creating features as an attribute of the line feature. One reason to do this is to keep a record of the original COGO description of the line features. This is useful if you need to research the original value when you are modifying the line feature in the future.

Not every command and tool in ArcMap updates the COGO attributes of a line feature. The Traverse window, 2-Point Line window, Cul-de-sac command, and Proportion command are examples of those that do update. For a complete list, see About COGO descriptions. To get this behavior, you need a line feature class with the appropriate COGO attributes. You can use the Create COGO fields command in ArcCatalog to do this.

How is COGO different from other ESRI COGO capabilities?

The COGO functionality provided when editing in ArcMap with the COGO toolbar allows you to create and maintain your land parcels and other surveyed features in a geodatabase. There is other ESRI functionality that provides similar capabilities, such as the Survey Analyst extension to ArcGIS and the COGO extension to ArcInfo Workstation.

ArcGIS Survey Analyst and Cadastral Editor

ArcGIS Survey Analyst is an extension to ArcGIS that allows you to capture and maintain survey information collected from field notes, data collectors, and record information submitted by surveyors to public authorities. You can use this survey information to incrementally improve the accuracy of GIS feature geometry in the geodatabase. See the Survey Analyst documentation for more information.

Survey Analyst is comprised of a Survey Editor and Cadastral Editor. The Cadastral Editor provides a new cadastral fabric dataset, job tracking, and workflow functionality for maintaining a land records database.
How does this differ from COGO?

COGO extension for ArcInfo Workstation

The COGO extension for ArcInfo Workstation provides functionality for capturing and maintaining land records data in a coverage. How does this differ from COGO in ArcGIS?

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