GPS TrackMaker Reference Manual page 66

Zoom Limits
Unlike the scale applied directly to Waypoints and Tracklogs, the zoom limits are applied to the whole MAP file.
This resource allows, for example, to create a general map with few details that is hidden in a specific zoom level.
At the same time, detailed maps may be shown in the same zoom level.
Zoom in Which the Map is Shown
Determines the level of zoom in which the map is shown on screen. Usually it is applied to detailed maps, with
many drawing elements that must be shown only in lower levels of zoom.
Zoom in which the Map is Hidden
Determines the level of zoom in which the Map is hidden on screen. This limit of zoom is mainly used in maps for
big scales and with few details that must be hidden in the moment that the detailed maps are shown.
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