We find some new expressions of density for straight lines and planes in euclidean spaces of dimension two and three. Also, we show the density for straight lines in surfaces which is expressed in terms of the coefficient of the first fundamental form. Finally, the density for tangent lines to a differentiable plane curve and for tangent plane of a differentiable surface are presented.
"About the Densities for Straight Lines in Semi-Riemannian Spaces." J. Geom. Symmetry Phys. 14 1 - 11, 2009. https://doi.org/10.7546/jgsp-14-2009-1-11