In this paper we characterize the family of secant lines of an ovoid of PG$(3,q)$ and the family of external lines to an ovoid of PG$(3,q)$.
Nicola Durante. Domenico Olanda. "A characterization of the family of secant or external lines of an ovoid of PG$(3,q)$." Bull. Belg. Math. Soc. Simon Stevin 12 (1) 1 - 4, April 2005. https://doi.org/10.36045/bbms/1113318124