  We perform test-particle simulations in a 2D, differentially rotating stellar
disk, subjected to a two-armed steady state spiral density wave perturbation in
order to estimate the influence of spiral structure on the local velocity
field. By using Levenberg-Marquardt least-squares fit we decompose the local
velocity field (as a result of our simulations) into Fourier components to
fourth order. Thus we obtain simulated measurements of the Oort constants, A,
B, C, and K. We get relations between the Fourier coefficients and some
galactic parameters, such as the phase angle of the Solar neighborhood and the
spiral pattern speed. We show that systematic errors due to the presence of
spiral structure are likely to affect the measurements of the Oort constants.
Moderate strength spiral structure causes errors of order 5 km/s/kpc in A and
B. We find variations of the Fourier coefficients with velocity dispersion,
pattern speed, and sample depth. For a sample at an average heliocentric
distance of 0.8 kpc we can summarize our findings as follows:(i) if our
location in the Galaxy is near corotation then we expect a vanishing value for
C for all phase angles;(ii) for a hot disk, spiral structure induced errors for
all Oort constants vanish at, and just inward of the corotation radius; (iii)
as one approaches the 4:1 indblad resonances |C| increases and so does its
variation with galactic azimuth; (iv) for all simulations |C|, on average, is
larger for lower stellar velocity dispersions, contrary to recent measurements.
