  Current and future galaxy surveys cover a large fraction of the entire sky
with a significant redshift range, and the recent theoretical development shows
that general relativistic effects are present in galaxy clustering on very
large scales. This trend has renewed interest in the wide angle effect in
galaxy clustering measurements, in which the distant-observer approximation is
often adopted. Using the full wide-angle formula for computing the
redshift-space correlation function, we show that compared to the sample
variance, the deviation in the redshift-space correlation function from the
simple Kaiser formula with the distant-observer approximation is negligible in
galaxy surveys such as the SDSS, Euclid and the BigBOSS, if the theoretical
prediction from the Kaiser formula is properly averaged over the survey volume.
We also find corrections to the wide-angle formula and clarify the confusion in
literature between the wide angle effect and the velocity contribution in
galaxy clustering. However, when the FKP method is applied, substantial
deviations can be present in the power spectrum analysis in future surveys, due
to the non-uniform distribution of galaxy pairs.
