In ArcGIS Explorer, you can specify how two-dimensional (2D) symbol units (originally expressed as printer's points) should be converted to real-world units such as feet or meters. As part of the Open Content wizard, you can specify the number of real-world units to which to convert symbol units. Take care when assigning the value, as symbols remain the same size in relation to the globe. They'll appear larger as you zoom in and smaller as you zoom out. If the real-world size is too small, the features may not be visible when viewed from a high altitude.