Fundamental domains in ${\rm PSL}(2,{\mathbb R})$ for Fuchsian groups

Abstract: In this paper, we provide a necessary and sufficient condition for a set in ${\rm PSL}(2,{\mathbb R})$ or in $T^1{\mathbb H}^2$ to be a fundamental domain for a given Fuchsian group via its respective fundamental domain in the hyperbolic plane ${\mathbb H}^2$.