The DOP (dilution-of-precision) coverage map shows the dimensionless DOP value for all receivers within the area or region. Example of a DOP coverage map (without thresholds):
More information and the possibility to update or export the map can be accessed through the [Update] menu entry of the window, which presents, for instance, a dialog like:
The threshold values provide a mean to color the map with only four colors, where the actual color depends whether a certain receiver point reaches at most the threshold as DOP value.