Methods and apparatus for facilitating detection of a presence or an absence of at least one underground facility within a dig area. Source data representing one or more input images of a geographic area including the dig area is electronically received at a first user location, which may be remote from the dig area. The source data is processed so as to display at least a portion of the input image(s) on a display device at the first user location. One or more indicators are added to the displayed input image(s), via a user input device associated with the display device, to provide at least one indication of the dig area and thereby generate a marked-up digital image. In one example, the indicator(s) is/are added to the displayed input image(s) without acquiring geographic coordinates corresponding to the indicator(s).