# Setting Options

Options contains user configurable settings.
The full Options Setting page is here: Options Setting
OpenCPN uses some basic settings or limitations.

- Courses are by default true, not magnetic. Change this in Options → Display → Units.
- All distances and routes are calculated using Mercator Sailing. Great Circle Sailing is an option in route creating.
- For Windows: only one instance of OpenCPN is allowed. Use the portable option if more instances are needed.
- Do not edit the opencpn.ini (opencpn.conf) file when OpenCPN is running.