If you’re using a custom image as the base layer, you can use this field (in conjunction with Top-most Coordinate, Left-most Coordinate, and Bottom-most Coordinate) to align your image with specific coordinates, so the nodes are displayed in your intended locations.

Enter a latitude in DD (decimal degrees) notation that coincides with the right border of the image. The default value is 180, which will place the right border of the image on the 180th meridian.