Multiple studies demonstrate that bathymetry can be effectively measured using non-sonar methods, including satellite altimetry, airborne gravity data, and multispectral satellite imagery.
The claim states that bathymetry can be measured using methods other than sonar. Papers [0], [1], [2], [3], [6], and [11] all explicitly discuss and demonstrate non-sonar methods for measuring underwater depth and seafloor topography (such as satellite altimetry, airborne gravity, and satellite-derived bathymetry from optical imagery). There are no papers refuting the claim, and the evidence entirely supports it.