Example of the closure phase variation in 3C 279 over four epochs for the large ALMA-SMT-SMA, ALMA-LMT-SMA, and ALMA-LMT-SMT triangles. The points show the data, and their error bars include 1.5% systematic visibility errors (Paper III). The solid lines show the model closure phases corresponding to the images from each pipeline and day, and the dashed lines represent the model closure phases of the average images shown in Fig. 4. Regions constrained by predictions of the three independent image models are shaded.