Use ground to grid corrections

Ground to grid correction is a drawing mode used with editing that converts ground measurements from grid geometry defined by the coordinate system of the feature data. It is turned on or off using the status bar at the bottom of the active map.

When ground to grid is turned on, direction values are rotated by the enabled offset angle, and distance values are scaled by the enabled distance factor.

When you use ground to grid corrections, consider the following:

• The scale factor can be specified as a constant value or as a combined scaled factor referencing elevation surfaces.
• Ground to grid correction is not available with 3D scenes.

Caution:

Changing correction settings while creating or modifying features can introduce slight differences in the geometries you create. As a best practice, confirm the correction settings before creating features.

Turn on ground to grid correction

To turn on ground to grid correction, on the status bar at the bottom of the active map, click the Ground To Grid button . Alternatively, hover over the button until the pop-up dialog box appears, turn on the Corrections toggle button, and move the pointer back to the map.

Set a direction offset

The direction offset specifies the rotation angle that is applied to direction values provided with ground to grid-aware tools:

• A positive angle rotates values counterclockwise.
• A negative angle rotates values clockwise.

For example, setting a direction offset of -5° and providing a ground direction of N40°E constrains the new segment at N45°E.

To set a direction offset, complete the following steps:

1. On the status bar at the bottom of the active map, hover over the Ground To Grid button until the pop-up dialog box appears.
2. Check or uncheck the Direction Offset check box.

   Checked	Line segments are rotated by the specified value when you are using ground to grid tools.
   Unchecked	Line segments are not rotated when you are using ground to grid tools.

3. Click the Direction Offset drop-down arrow and set the direction units.
4. In the Direction Offset text box, provide the offset angle for the specified units.
5. Click the map to close the dialog box and save your settings.

Set a distance factor

The distance factor specifies the scale factor that is applied to ground distance values you provide when using editing tools.

For example, setting a distance factor of 0.95 and providing a ground distance of 100 feet creates or constrains the new segment to 95 feet.

To set a distance factor, complete the following steps:

1. On the status bar at the bottom of the active map, hover over the Ground To Grid button until the pop-up dialog box appears.
2. Check or uncheck the Distance Factor check box.

   Checked	Line segments are scaled by the specified value when you are using editing tools.
   Unchecked	Line segments are not scaled when you are using editing tools.

3. Configure how the distance factor value is specified by doing one of the following:
   • Provide a value in the Constant scale text box to scale all distances by this value.
   • Use Compute from elevation mode to compute a combined scale factor using z-values generated by the current elevation mode and the coordinate system for the active map. You can set the elevation mode to a constant z-value or set it by clicking an elevation surface using the pointer.

     Note:

     This setting computes a combined scale factor using map projection information and the location and elevation of the data being edited. The scale factor updates dynamically on the corrections display as you move the pointer and create features.

4. Click the map to close the dialog box and save your settings.

Provide the ground line and draw the grid line

You can compute correction values by comparing provided ground values with the equivalent grid line drawn in the map.

For example, you can provide a known basis of bearing values for direction and distance and click the two monuments in the map to compute the correction. A ground direction of N40°E and a drawn grid line at N45°E sets the direction offset to -5°. A ground distance of 100 feet and a drawn grid line at 95 feet sets the distance factor to 0.95

To provide the ground line and draw the grid line, complete the following steps:

1. On the status bar at the bottom of the active map, hover over the Ground To Grid button until the pop-up dialog box appears.
2. Click Enter the ground line and draw the grid line .
3. Provide the known ground values for direction and distance.
   1. Click the Direction Offset drop-down arrow and set the direction units.
   2. In the Direction Offset text box, provide the offset angle for the specified units.
   3. Click the Distance drop-down arrow and set the units.
   4. In the Direction text box, provide the distance for the specified units.

      To preserve the current constant scale setting and update only the direction offset, provide or accept the default value of zero (0).

4. Click Next.
5. Draw the grid line using the pointer by following the on-screen prompts that appear in the upper right corner of the map.
   1. Click the start point of the grid line.
   2. Click the end point of the grid line.

Draw a ground line and a grid line

You can also compute correction values by comparing a line drawn in the map using direction and distance values with an equivalent grid line also drawn in the map.

For example, drawing a ground line at N40°E and a grid line at N45°E sets a direction offset of -5°. Drawing a ground line of 100 feet and a grid line of 95 feet sets a distance factor of 0.95.

1. On the status bar at the bottom of the active map, hover over the Ground To Grid button until the pop-up dialog box appears.
2. Click Draw the ground line and draw the grid line .
3. Draw the ground line using the pointer by following the on-screen prompts that appear in the upper right corner of the map.
   1. Click the start point of the ground line.
   2. Click the end point of the ground line.
4. Draw the grid line using the pointer by following the on-screen prompts that appear in the upper right corner of the map.
   1. Click the start point of the grid line.
   2. Click the end point of the grid line.