Fitting of the CME shock with the GCS model at four different times: (a) 11:05, (b) 11:10, (c) 11:15, and (d) 11:20 UT. The panels show the fit as seen from STEREO-B (left) and Earth (right). In addition, panel a shows the location of the observing spacecraft relative to the Sun. The GCS model (blue) is overlaid on the EUV and white-light running difference images. The EUV observations consist of STEREO/SECCHI/EUVI-B at 195 Å and SDO/AIA at 211 Å. The white-light observations were mainly made by STEREO/SECCHI/COR1-B, with the exception of the right panel in c where SOHO/LASCO C2 data was available. The time interval between the images used to produce the running difference images is 5 min for both EUVI-B and COR1-B and 12 min for LASCO C2.