measuring vertical movement in a container
many rang finding options exist .. take your pick


Ultrasonic (cheap, easy works over temperature accuracy is an issue)
Laser range finder (expensive, accurate, works over temperature)
inductive/capactive (depends on details of your application is this will be suitable)
77 GHz radar - for example has great resolution and is being used in automotive collision avoidance and cruise control as well as depth sensing of grain silos)
Pressure sensor ??  - not sure if there will be a pressure change due to your environment
many other possibilities: it really depends on your specific application requirement