Stack Exchange network consists of 183 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.
If $f$ is piecewise $C^2$, since your map is piecewise expanding it has an ACIM. See Lasota and York (Trans AMS, 1973).
See also the Chaos, Fractals, and Noise by A. Lasota and M. Mackey. One of the theorems in Ch. 6 might work for your maps.