  We present a modification of the relativistic phase shift method of
determining the radio emission geometry from pulsar magnetospheres proposed by
Gangadhara & Gupta (2001). Our modification provides a method of determining
radio emission altitudes which does not depend on the viewing geometry and does
not require polarization measurements. We suggest application of the method to
the outer edges of averaged radio pulse profiles to identify magnetic field
lines associated with the edges of the pulse and, thereby, to test the
geometric method based on the measurement of the pulse width at the lowest
intensity level. We show that another relativistic method proposed by
Blaskiewicz et al. (1991) provides upper limits for emission altitudes
associated with the outer edges of pulse profiles. A comparison of these limits
with the altitudes determined with the geometric method may be used to probe
the importance of rotational distortions of magnetic field and refraction
effects in the pulsar magnetosphere. We provide a comprehensive discussion of
the assumptions used in the relativistic methods.
