A new project-level setting for the scale calculation method has been added, with choices for:

• at top of map
• at bottom of map
• at middle of map
• horizontal average
• scale at equator

Changing the scale method impacts numerous system behaviors, including:

• New layout scale bars will default to the project's scale calculation method
• The scale calculations will be adjusted, affecting project aspects including:
  • status bar widget map renders
  • @map_scale and similar scale-related API methods
  • scale based visibility of layers and symbols
• Processing algorithms which render maps will respect the project scale calculation method
• Scale method affects QGIS server map rendering

Note that symbology sizes determined in map units are NOT affected by this setting.
The new "scale at equator "scale calculation method always calculates the scale at the equator, regardless of the actual visible map extent. It can be used to provide a consistent, static scale for maps in geographic reference systems, regardless of the latitudes actually visible in the map. Note that this method is only applicable when calculating scales with a degree-based reference system.