The mercator scale bar is a customized scale bar displayed on aeronautical charts using a mercator projection.
![Mercator Scale Bar Mercator Scale Bar](GUID-3F99AED4-270E-4DC8-AAB3-1C8F718C51FD-web.gif)
- Start ArcMap.
- On the main menu, click View > Layout View.
- On the main menu, click Customize > Toolbars > Aviation Layout.
- Click the Mercator Scale Bar button
on the Aviation Layout toolbar.
By default, the mercator scale bar represents the current focus map scale if it is not zero.