The proper motions of the H_2O masers in W49N have been measured
with multi-epoch very-long-baseline interferometry (VLBI) by
Gwinn, Moran, and Reid (1992). The number of motions measured is
large (105), and the spatial coverage of the source by maser-emitting
spots with measured motions is excellent, making this source a prime
candidate for investigation with model-independent analytic tools
involving diagonalization of the velocity variance-covariance
matrix (VVCM), as described by Bloemhof (1993).
Moreover, unlike the case of OH masers, the HII region is essentially
transparent at the frequency of the H_2O maser transition, so a full
three-dimensional treatment is straightforward.
In any VLBI proper motion experiment, the absence of an absolute
interferometric phase reference implies that absolute velocities
are not known, so the velocity dispersions (or relative velocities)
of VVCM diagonalization are the natural quantities with which to work.
In this paper, I report on the results of applying VVCM diagonalization
to W49N, deriving the kinematic axis of the outflow accompanying a region
of massive star formation. I then compare this local axis with the angular
momentum axis suggested by the morphology of the ring of HII regions that
accompany the one containing the H_2O masers, and with the axis of the
large-scale outflow seen in CO emission.