  EUV waves are large-scale disturbances in the solar corona initiated by
coronal mass ejections. However, solar EUV images show only the wave fronts
projections along the line-of-sight of the spacecraft. We perform 3D
reconstructions of EUV wave front heights using multi-point observations from
STEREO-A and STEREO-B, and study their evolution to properly estimate the EUV
wave kinematics. We develop two different methods to solve the matching problem
of the EUV wave crest on pairs of STEREO-A/-B images by combining epipolar
geometry with the investigation of perturbation profiles. The proposed
approaches are applicable at the early and maximum stage of the event when
STEREO-A/-B see different facets of the EUV wave, but also at the later stage
when the wave front becomes diffusive and faint. The techniques developed are
demonstrated on two events observed at different separation of the STEREO
spacecraft (42$^\circ$ and 91$^\circ$). For the 7 December 2007 event, we find
that the emission of the EUV wave front mainly comes from a height range up to
90-104 Mm, decreasing later to 7-35 Mm. Including the varying height of the EUV
wave front allows us to correct the wave kinematics for the projection effects,
resulting in velocities in the range 217-266 km/s. For the 13 February 2009
event, the wave front height doubled from 54 to 93 Mm over 10 min, and the
velocity derived is 205-208 km/s. In the two events under study, the corrected
speeds differ by up to 25% from the uncorrected ones, depending on the wave
front height evolution.
