We propose a novel method for constructing a pseudo-synoptic view of estuarine features from nonsynoptic observations captured by mobile platforms. The model-aided Lagrangian interpretation (MALI) method is based on relocating observations to a common reference moment in time along three-dimensional Lagrangian trajectories derived from a numerical model of estuarine circulation. The method relies on the model skill to capture large-scale circulation features, and on high-resolution in situ observations to characterize small-scale hydrographic structure. We demonstrate our technique by applying MALI to autonomous underwater vehicle observations in the Columbia River estuary, with the aid of a validated unstructured-grid finite-element numerical simulation. The method can be readily adapted to a broader range of environments, observational platforms, and model-data combinations.Hydrographic transects conducted with mobile platforms are invaluable to understanding the distribution and exchange of salt, sediments, nutrients, biota, and pollutants in estuaries. In the environments characterized by strong tidal and riverine flows, such as the Columbia River, transect surveys are rarely synoptic: As the speeds of the surveying platform and the natural flow are typically of the same order of magnitude, scalar and circulation features typically change drastically during the time window of the transect.The conventional presentation of results of estuarine surveys in the form of transects along geographic coordinates gives a false impression of synoptic "snapshots" of the tracer fields ( Fig. 1a-c). Even though the non-synopticity of the transects is typically acknowledged, the implied distorting effects of the concurrent advection is visually difficult to ascertain. As a result, distortions can be easily overlooked or dismissed, potentially leading to misinterpretation of the observed features or miscalculation of their spatial relationships, extent, and propagation speed.To alleviate the distorting effects of estuarine advection during surveys, we propose relocation of the observations along the model-derived three-dimensional (3D) Lagrangian particle trajectories to a common reference time, thus obtaining a synthetic pseudo-synoptic view (Fig. 1d,e).