Top (from left to right): (u,v) coverage, PIONIER V² and closure phases; for a given quadruplet, every baseline “observation” consists of 3 measurements at 1.58 μm, 1.67 μm, and 1.76 μm; For each closure phase, B_max is the projected length of the longest baseline of the triplet. Bottom (from left to right): (u,v) coverage, and AMBER K-band V²; every baseline “observation” consists of V² measurements between 2 μm and 2.5 μm.