  The accurate sky localization of gravitational wave (GW) sources is an
important scientific goal for space-based GW detectors. Due to the effects of
gravity on three spacecrafts, it is hard to maintain the equality of the arm
length, so the time-delay interferometry (TDI) method is needed to cancel out
the laser frequency noise for space-based GW detectors. By considering the
first-generation TDI combination, we employ the Fisher information matrix to
study the accuracy of sky localizations for future space-based GW detectors and
their combined network. The main difference between future space-based GW
detectors includes the time-changing orientation of the detector plane, the arm
length, the orbital period of spacecrafts and the noise curve. We study the
effects of these factors on the accuracy of source localization at different
frequencies. We find that the amplitude modulation caused by the rotation of
the detector plane can help LISA and Taiji not only to improve the accuracy of
source localization but also to enlarge the sky coverage at frequencies below 1
mHz. As the frequency of monochromatic GWs increases, the Doppler modulation
becomes dominate and the equatorial pattern appears in the sky map. The effect
of arm length on the angular resolution mainly comes from the noise curve and
it is almost the same for both heliocentric and geocentric constellations. The
orbital period of the spacecrafts has little effect on the angular resolutions.
The improvement on the angular resolutions by the network of combined detectors
is small compared with a single detector and the angular resolutions are almost
the same with and without the TDI combination.
