  We propose a continuous data assimilation (CDA) method to address the
uniqueness problem for steady Navier-Stokes equations(NSE). The CDA method
incorporates spatial observations into the NSE, and we prove that with
sufficient observations, the CDA-NSE system is well-posed even for large data
where multiple solutions may exist. This CDA idea is in general helpful to
determine solution for non-uniqueness partial differential equations(PDEs).
