Procedure to compute the BSVR. A sample GALEX image is displayed in the leftmost panel, as well as the central square used to compute the BSVR. This central square rebined into an image of 64 × 64 resels which is displayed in the central panel. From the inverse of this image, a vector, V, is constructed by re-arranging its elements (see text); they are plot in the right panel. The envelopes in this panel are constructed as follows: every 400 elements, the mean (white line), the maximum, and the minimum (bold dashed lines) are computed. The BSVR is determined from these values (see text for further details).