By adding the precovery observations of 1939, the orbit determination
becomes so accurate that the target plane uncertainty for the 2004
encounter is very much reduced. The semiaxes of the
ellipse
are 240 and 1200 km; the semilinear boundary has a similar size,
although its shape is distorted. This refers, however, to a portion of
the MTP centered at the nominal miss distance of
km from the
center of the Earth, that is well inside the Earth volume.
Since the Earth surface is 2-dimensional, basically the same
mathematical formalism described in Section 2.2 could be used to draw
confidence boundaries of the impact point.