3.1.2 Solution along characteristic curves

Characteristics already discussed for a quasi-linear PDE (Sect. 2.1.5).

Velocity $v_{}$ is not globally constant anymore.

However, it is constant along characteristic

$$c(t) = v_{} \! \left( x_0 \right) t + x_0 \enspace .$$ (162)

That allows a graphical ``solution'' by using characteristics.