Example of the baseline removal process for the GBT observations. Upper panel: raw data (in black) and the polynomial (green dashed line) used to remove the shape of the bandpass from the data. In this example a polynomial of order five was used. The red and blue dotted lines show the ranges where we expect the RRLs. These ranges are not considered while fitting the polynomial. Bottom panel: data after subtraction of the polynomial used to capture the bandpass shape. The velocity axis is referenced with respect to the rest frequency of the corresponding CRRL. This data is part of project AGBT12A_484.