Defining Minimum Safe Altitude (MSA) settings

The Minimum Safe Altitude (MSA) circle is found in the plan view of Instrument Approach Procedure (IAP), Standard Instrument Departure (SID), and Standard Terminal Arrival Route (STAR) charts. The MSA circle, which may contain one or several sectors, indicates the minimum safe altitude that provides 1,000-foot or 300-meter obstacle clearance at a specific distance, from the Navaid, Airport, Waypoint, and so forth, at the center of the MSA circle. The MSA circle contains bearings, altitudes, Navaids, Airports, Waypoints, and so forth, that correspond to the chart on which the MSA resides. An MSA element is a graphical depiction of the altitude that allows adequate vertical clearance from nearby terrain and man-made obstacles, allowing proper navigational functions.

New MSA elements are created based on the Minimum Safe Altitude settings on the Element Settings pane on the Production Properties dialog box. These properties determine the default appearance and style of the newly created MSA elements. Changing the settings does not alter existing MSA elements. Existing MSA elements can be updated by clicking the MSA Element tool, which will regenerate the MSA element based on updates to the data and/or the settings. The significant point on which the MSA element is based is defined in the MSAGroup feature class in the production database.

Steps:

1. Start ArcMap.
2. On the main menu, click Customize > Production > Production Properties.

   The Production Properties dialog box appears.

3. Click the Element Settings pane.
4. In the Minimum Safe Altitude section, click the cell next to Circle Diameter Units, click the drop-down arrow that appears, then choose the unit of measurement of the circle diameter.
5. Click the cell next to Circle Diameter and type the value you want.
6. Click the cell next to Circle Line Symbol, click the ellipsis button (...) that appears, then modify the circle line symbol properties.
7. Click the cell next to Identifier Font, click the ellipsis button (...) that appears, then modify the identifier font properties.
8. Click the cell next to Altitude Font, click the ellipsis button (...) that appears, then modify the altitude font properties.
9. If necessary, click the cell next to Reset Settings, click the drop-down arrow that appears, then choose True if you want to undo all the changes made to the MSA settings and restore the default settings.
10. If necessary, click the cell next to Show Bounding Box, click the drop-down arrow, and choose True if you want the MSA element to render with a box surrounding it.
11. If necessary, click the cell next to Bounding Box Height and type a height value.

    The default value is 0.5 inches. You can change the unit type using the Bounding Box Units drop-down list.

12. If necessary, click the cell next to Bounding Box Width and type a width value.

    The default value is 0.5 inches. You can change the unit type using the Bounding Box Units drop-down list.

13. If necessary, click the cell next to Altitude Display Units, click the drop-down arrow, and choose an altitude unit.
14. If necessary, click the cell next to Bearing Arrow Symbol and click the ellipsis button (...) that appears.
15. If necessary, click the cell next to Bounding Box Units, click the drop-down arrow that appears, then choose a different unit.
16. If necessary, click the cell next to Box Fill Symbol and click the ellipsis button (...) that appears.

    This allows you to change several properties of the bounding box fill symbol, including fill color and outline width and color.

17. If necessary, click the cell next to Identifier Display Order, click the drop-down arrow that appears, and choose a different option.
    Note:

    This setting controls the order of elements in the identifier string. The Ident First option specifies MSA SNS 25 NM while the Ident Last option indicates MSA 25 NM SNS.

18. If necessary, click the cell next to Identifier Display Style, click the drop-down arrow that appears, and choose either Straight or Curved.
    Note:

    The Identifier Location setting determines where the Identifier is placed.

19. If necessary, click the cell next to Identifier Display Units, click the drop-down arrow that appears, and choose a unit.
20. If necessary, click the cell next to Identifier Display Location, click the drop-down arrow that appears, and choose either Top or Bottom.
21. If necessary, click the cell next to Show Altitude Bounding Box, click the drop-down arrow that appears, and choose either True or False.
    Note:

    An altitude bounding box is a rectangular box around an altitude value within the MSA element.

22. If necessary, click the cell next to Show Altitude Units, click the drop-down arrow that appears, and choose either True or False.
    Note:

    Altitude unit type is controlled by the Altitude Display Units setting.

23. If necessary, click the cell next to Show Center Symbol, click the drop-down arrow that appears, and choose either True or False.
24. Click OK to save the settings you have modified.

    These settings are applied to the new MSA elements you create in the future, unless the settings are modified again.