The map interface displays the effective spatial domain reconstructed from the GRIB grid (computed from grid-point centres expanded by half the grid resolution).

The user must place a station reference point inside this domain and confirm the selection using the “Use pin coordinates” button.

Inserting and managing the station pin

The map follows a simple macOS interaction logic:

• “+” button
  Enables pin insertion mode at the center of the map.

• Pin drag & drop
  Once inserted, the pin can be repositioned by dragging it to a new location.

• “−” button
  Removes the currently placed pin.
  After deletion, a new pin can be inserted using the “+” button.

Only one station pin can exist at a time.

When confirmed:

• WindRose identifies the nearest ERA5 grid node physically contained in the GRIB dataset.

• That grid node becomes the projection point in case of point-based analysis.

If a station reference point was previously confirmed, WindRose remembers it and restores it automatically when reopening this window.
The stored reference is reset only when a new GRIB file is opened.

Depending on the selected projection policy:

• Point-based projection uses the nearest grid node to the confirmed station reference point.

• Area-averaged projection computes averages across all grid nodes physically contained within the GRIB domain.

The exported spatial files (SHP or KML) reflect the chosen projection policy and include:

• The effective spatial domain

• All grid-point centres contained in the GRIB file

• The selected projection grid node (in point-based mode).