  State-of-the-art techniques to identify H\alpha emission line sources in
narrow-band photometric surveys consist of searching for H\alpha excess with
reference to nearby objects in the sky (position-based selection). However,
while this approach usually yields very few spurious detections, it may fail to
select intrinsically faint and/or rare H\alpha-excess sources. In order to
obtain a more complete representation of the heterogeneous emission line
populations, we recently developed a technique to find outliers relative to
nearby objects in the colour-magnitude diagram (CMD-based selection). By
combining position-based and CMD-based selections, we built an updated
catalogue of H\alpha-excess candidates in the northern Galactic Plane. Here we
present spectroscopic follow-up observations and classification of 114 objects
from this catalogue, that enable us to test our novel selection method. Out of
the 70 spectroscopically confirmed H\alpha emitters in our sample, 15 were
identified only by the CMD-based selection, and would have been thus missed by
the classic position-based technique. In addition, we explore the distribution
of our spectroscopically confirmed emitters in the Gaia CMD. This information
can support the classification of emission line sources in large surveys, such
as the upcoming WEAVE and 4MOST, especially if augmented with the introduction
of other colours.
