The destinations are normally given as the geographic centre of an ancient site, or the most visible remains, such as a theater; it is not necessarily the final water distribution structure of the aqueduct channel itself, since the position of these is in most cases unknown.
The accuracy of the position of aqueduct channels is strongly variable, since it depends on the accuracy of maps in the published literature. The green line is simply our best estimate of the position of the aqueduct channel. We are improving the accuracy of these tracks wherever possible.
Since aqueduct channels are nearly always highly curved, following contour lines, it is relatively easy to judge the accuracy of a certain aqueduct trace on our maps; a highly curved track with many nodes is more accurate than a straight one with few nodes. In some cases, where only source and destination are known, the aqueduct channels is simply indicated as a straight line connecting both, although the real track must have a more complex shape.