Two questions stand between the ruling and the drawing: which hand the chart is drawn in, and how a flat map holds a round bead. Both are answered here in line, not in words.
The same object, the same light, drawn twice. Neither is a texture or a filter: every line is placed, and its weight is the shadow it sits in.
A printing technique. One line, laid mechanically, swelling into the shadow and tapering to nothing in the light; cross-hatch only where the form turns away. No outline — the form ends where the line ends, and the bare paper is the highlight.
A drawing technique. One nib of one weight; tone built by spacing and repetition, strokes laid across the form rather than around it, a contour visibly made by a hand, and the ends of the strokes left ragged.
The proposed boundary: engraving is a printing technique, sketching is a drawing technique. Carta takes the burin; Praesidio keeps the pen and pencil that §4.4.2 made its hallmark. They read as different at a glance, and neither borrows the other.
An engraved chart was already a three-dimensional medium — it is how relief was drawn before photography. The meld is not a compromise between a map and a 3-D look; it is one technique, and the map’s own furniture carries the navigation.
A fragment, at a tenth of the real strand. Oblique projection, no vanishing point, so the plate tiles and a bead can be added without redrawing anything. Depth by line density. One light, upper left, on every element.