6. Remove artifacts

Stratigraphic diagrams, and especially pollen diagrams, often have a lot of artifacts in it, that are informative for the reader.

In our case, the diagram is splitted into three temporal zones (HDC-2, HDC-3 and HDC-4, see the Zone column on the right part of the diagram) which are visually separated with horizontal lines. Additionally, the diagram has vertical, dashed lines at each column start (the y-axes for each column).

Before we digitize our diagram, those informative features have to be removed. You can do this in an external image editing software (e.g. Photoshop) but we also implemented several automated algorithms to detect common features and remove them easily.

For our tutorial, we use the Remove lines feature to detect and remove the vertical and horizontal lines.

Horizontal lines

  1. Expand the Remove features tab in the Digitization control

  2. Expand the item with the vertical lines and horizontal lines button by clicking on the small arrow on their left

  3. Set the minimum line width to 1 pixel

  4. Click the horizontal lines button. In the plot you will see, that the horizontal lines are red now (if necessary, go with the mouse over the plot and you will see it in the zoom window). You could edit the selection now using the selection toolbar (see The selection toolbar), but for our tutorial, this is not necessary.

  5. Click the Remove button to remove the lines

Vertical lines (y-axes)

  1. Enable the maximum line width and set it to 2 pixel

  2. Set the minimum fraction to 30%

  3. Click the vertical lines button and the vertical lines turn red and are marked to be removed.

  4. Click the Remove button to remove the y-axes

Additional automated removal tools are available and fully described in the documentation (see Removing features). But here, we can continue with the digitization.