A typical fit to the data of one of our sources, HD 3379. On the left, we show the u − v coverage of the PIONIER observations. The different colours correspond to the telescope pair with which the particular data were acquired at the VLTI. In the middle, we show the closure phase (T3PHI) fit and residuals in terms of the spatial frequency (B_avg/λ; written as Bavg/wl on the axes). On the right, we show the fit to the squared visibilities (V2) and the associated residuals, again in terms of spatial frequency. The data are represented as points in the fits, whilst the model fits are shown as continuous lines.