On the structural result on normal plane maps

We prove the structural result on normal plane maps, which applies to the vertex distance colouring of plane maps. The vertex distance-t chromatic number of a plane graph G with maximum degree Δ(G) ≤ D, D ≥ 12 is proved to be upper bounded by $6 + [(2D+12)/(D-2)]((D-1)^{(t-1)} - 1)$. This improves a recent bound $6 + [(3D+3)/(D-2)]((D-1)^{t-1}-1)$, D ≥ 8 by Jendrol' and Skupień, and the upper bound for distance-2 chromatic number