  In the numerical modeling of the GRB afterglow, some approximations have been
made for simplicity, and different groups developed their codes. A robust test
of these models/approaches is challenging because of the lack of directly
measured physical parameters. Fortunately, the viewing angle inferred from the
afterglow modeling is widely anticipated to be the same as the inclination
angle of the binary neutron star (BNS) mergers that can be evaluated with the
gravitational wave (GW) data. Therefore in the future, it is possible to
calibrate the afterglow modeling with the GW inclination angle measurements. We
take three methods, including both analytical estimations and direct
simulations, to project the uncertainties of the inclination angle
measurements. For some BNS mergers accompanied with electromagnetic
counterparts detected in the O4/O5 runs of LIGO/Virgo/KAGRA/LIGO-India
detectors, we show that the inclination angle can be determined within an
uncertainty of $\leq 0.1$ rad, supposing that the Hubble constant is known with
an accuracy of $\leq 3\%$ and the uncertainty of Hubble flow velocity is within
$\sim 1 \%$. The off-axis GRB outflow will give rise to afterglow emission, and
the most energetic ones may be detectable at the distance of $\sim$ 100-200 Mpc
even for a viewing angle of $\geq 0.3$ rad. Such events can thus serve as a
robust test of the afterglow modeling approach. We have also evaluated the
prospect of resolving the so-called Hubble tension with a single GW/GRB
association event. We find out that a $\sim 3\%$ precision Hubble constant is
obtainable if the uncertainty of the viewing angle can be constrained to be
within $\sim 0.1$ rad, which is expected to be the case for some nearby ($\leq
250$ Mpc) bright/on-axis GRBs with a well-behaved afterglow light curve
displaying a clear achromatic break at early times.
