Setting up the digitization station

and how to solve contrast issues...

The COBECORE project relies on the optimal digitization of the meteorological records, the first step in valorizing the data. In a conventional digitization setup it is suggested to use a black background to the works you digitize. This enhances the contrast between the work you digitize and the surroundings and makes it easy to automatically extract (crop) this work from the frame. The latter is especially important if the size of the work varies, or the setup is altered between digitization runs.

Given that the meteorological records are recorded on various formats the setup is not truly fixed. As such the conventional black background would be desired. However, through experimentation we found that the carbon copy paper on which a lot of these data are stored transmit a fair amount of background colour. This was less than desired, as the writing on the paper is often low contrast to begin with. In technical terms, the combination of a black background with highly transparent carbon copy paper decreased the signal to noise ratio (Fig 1, showing the same section on either a black and white background).

Fig 1. - comparison between a white and black background

We resolved this issue by creating dedicated black cardboard cutout masks for the most common paper formats on which data was noted (Fig 2). These masks make it easy to automatically crop the images to their approximate page size, while still keeping the high contrast due to the white background of the reproduction stand’s baseboard. With these issues resolved the digitalization station or digitstation is now fully configured and ready for some long runs (Fig 3).

Fig 2. - Mask setup, with black cardboard cutout
Fig 3. - Digistation setup, including the reproduction stand, lights, computer for direct image transfer and a background mask.

BLOG
digitization image_processing