About direction measuring systems and units

Some editing tools allow you to enter an angle, direction, or deflection when creating features. You can change the direction measuring system and units these tools use on the Units tab of the Editing Options dialog box. When you change the direction measuring system and units, the editing tools will all recognize inputs in the new system and units.

Sometimes when creating features using the coordinate geometry tools in ArcMap, you need to convert angles and distances measured in the field so they match the coordinate system of your data. This is known as a ground to grid correction. To learn more, see Applying a ground to grid correction.

Direction measuring systems

You can choose from the following direction measuring systems: north azimuth, south azimuth, quadrant bearing, and polar. By default, the tools accept angular measurements in the polar direction measuring system.

Direction measuring units

The editing tools use decimal degrees as their default units of angular measure. You can choose from the following direction measurement units: decimal degrees, degrees/minutes/seconds, radians, gradians, and gons.

Setting the ground to grid correction

When you read the COGO descriptions for boundaries on a survey plan or other legal document, the directions and distances are measured on the surface of the earth. These are referred to as ground measurements. However, the directions and distances in your GIS data are based on the spatial data's coordinate system, or the grid measurements.

Ground and grid measurements are often different. You set constants (the ground to grid correction) for directions and distances so that the software can correctly convert between the ground and grid measurements.

For details, see Applying a ground to grid correction.

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10/24/2012