The wording is misleading. You need to compute the angle of incidence of the incoming wavefront to a high accuracy in order to localize the source. The key qu

The wording is misleading. You need to compute the angle of incidence of the incoming wavefront to a high accuracy in order to localize the source. The key quantity is not the absolute delay introduced by the absolute distance from antenna to antenna (which is tens of meters, http://www.atnf.csiro.au/projects/askap/ska.html http://www.atnf.csiro.au/projects/askap/ska.html). It's the differential delay as a function of incidence angle.