The invention relates to methods of reliably and quantitatively determining the amount of an analyte of interest in a fluid sample using a flow-induced assay, such as an immunochromatographic assay, in which spatiotemporal measurements are recorded during the course of the assay reaction, generating a spatiotemporal dataset, and subsequently analyzed. The invention also relates to a system incorporating instruments for recording spatiotemporal datasets (spatiotemporal data recorders), devices comprised of flow-induced assays configured for analysis on a spatiotemporal recorder, and programs for analyzing the recorded spatiotemporal datasets.