Sefran broom wagon might deteriorate images when the archive source is not complete

[beaudu]

The sefran3 broom wagon (BW) rebuilts any image on fixed criteria (thresholds on dead channel number and % of gap). An issue might happen if the archive source is less complete or inaccessible, thus the BW will make an image with less data than the original, or worth, delete all channels making a blank image.

We propose to compare the data quality/completeness of the old and new image and update only the process improves the image. An other advantage will be an optimization of the BW process when the archive and realtime sources are identical (no improvement of the image): presently the BW rebuilts the image.