  We present the CIDA-UCM-Yale (Centro de Investigaciones de Astronomia,
Universidad Complutense de Madrid and Yale University) survey for
Halpha+[NII]6549,6584 emission-line galaxies using objective-prism spectra. The
most important properties of a catalogue with 427 entries and significant
subsets are analysed. The complete sample contains 183 statistically confirmed
ELGs in a sky area of 151 sq.deg. and redshift up to 0.14. We determine the
parameters of the Halpha luminosity function using the Halpha+[NII] flux
directly measured on the ELGs spectra in this sample and the star formation
rate density derived is in agreement with the values reported in the
literature. Finally, we study the clustering properties of local star-forming
galaxies relative to quiescent ones from different perspectives. We find that
emission-line galaxies avoid dense regions of quiescent galaxies and we propose
a power-law expression to parametrise the relation between star formation rate
density and environment volume density of emission-line galaxies.
