Seismic data are routinely inverted for impedances to quantitatively predict reservoir properties. Calibrations between rock properties and impedances are used to make predictions away from well control. The quality of these predictions depends on many factors, including the amount of impedance variations in rock properties, quality of the seismic data, and reliability of the impedance volume. The rock property impedance variations are dictated by geology and are set. The seismic data quality can always be improved, but at some point we are left to work with the data in their current states.