The system includes a dual interferometer sub-system configured to measure flatness across a substrate. The system includes a mass sensor configured to measure the mass of the substrate. The system includes a controller communicatively coupled to the dual interferometer sub-system and the mass sensor. The controller includes one or more processors. The one or more processors are configured to execute a set of program instructions stored in memory, the set of program instructions configured to cause the one or more processors to determine a thickness distribution of at least one of the substrate or a film deposited on the substrate as a function of position across the substrate based on one or more flatness measurements from the dual interferometer sub-system and one or more mass measurements from the mass sensor.