Schematic of the (3+1)D traveler kinematic for describing changes in map-position "x" regardless of speedP. Fraundorf (2012) "A traveler-centered intro to kinematics", arxiv:1206.2877 . using the traveler's perspective on time τ, velocity d"x"/dτ, and proper-acceleration "α". The method outlined here should in principle work with other metric equations as well.