Monochrome maps that show land and water face the challenge of finding a way to show which parts of the map are land and which are water in a reliable and intuitive manner. A careful map reader can always figure out which is which by doing things like looking for roads and cities, then noting what kind of shading of symbols lie underneath those features. Whatever that symbol is, it must mean land. Or the reader can look for marine features — shoals, wrecks, moorings, etc. — and correctly conclude that whatever symbol lies underneath those features must be water. A good map, and a responsible cartographer, does not make the map reader go through those mental gymnastics in order to interpret the map. A good map is easy to read quickly and interpret correctly, even if he map reader is not paying a lot of attention.

Color maps can dodge a lot of these problems. Almost any blue-ish color will be interpreted as water, though, again, a responsible map-maker will ensure that the water features actually look something like water, rather than just a blob of blue. A little bit of texture, or a hillshade of the bottom of the waterbody will make an area of water look, intuitively, like water.

For a monochrome map, making water and land intuitively obvious can be a bit trickier. Here are a few ways to attack the problem.

Shading the edge of the land area can create the illusion of land sloping downward, toward the water. This stippling shown below, which is denser and darker close to the shoreline then lightens away from the water’s edge, provides and even stronger visual signal that there is a downward slope toward the water. However, while this kind of shading is intuitively obvious for some map readers, some see the stippling as a symbol for a sandy beach that drops off into deep water as the dots get farther apart — exactly opposite the intended signal. The stylized trees are another way to get around that problem.

The dash-dot-dot-dot pattern on the map below is fairly common in 19th century maps. It has the same effect as the stippling shown above, by creating an illusion of a downward slope toward deep water. It also creates a bit of an illusion that the water area is slightly tinted, as though a very thin wash of ink had been applied. Both effects signal to the reader which part of the image is land and which is water. Some readers, however, find the dashes and dots visually distracting. They also make it impossible to put text close to shore.

An ink wash is perhaps the most effective way to signal the presence of water to a map reader. In the illustration below, the wash communicates additional information, by showing the map reader where the tide flats and deep channels are located. And, unlike the dash-dot technique, and ink wash can be made light enough that it’s possible to put text or other symbols — like the shoals and wreck in the map below — in the water area.

Ink washes, however, are very difficult to scan and reproduce clearly. Particularly when combined with black text, they often scan poorly or require hours of delicate adjustments to brightness and contrast (using the scanning software or something like Photoshop or the GIMP). After fighting with software for a very long time, I finally switched to a two-state workflow to get the grayscale of the ink wash and the black of the text and line are to reproduce well. The process (noted here to help my memory, too) goes like this:

1. Paint the gray for the waterbody on heavy paper that will not wrinkle. Don’t outline it with black ink; if an outline is needed for painting the water area, use a light pencil line.
2. Scan the ink wash of the waterbody and adjust the brightness and contrast so the lightest gray is clearly darker than the paper but so that the rest of the paper remains pure white.
3. Lay a piece of lightweight layout bond paper over the grayscale image (or over a printed copy of the scan of the grayscale image). Using a black pen (this is a Pigma Micron 01), draw the line art — the shoreline, shoals, islands, wrecks, etc. Then put a sheet of paper lined with the desired spacing of the text under the layout bond and do the lettering with black pen.
4. Scan the black and white line work and text. If you work in GIMP:

• Save it in .png file format
• Open it in GIMP. Change to RGB mode (not “indexed color”)
• Add a alpha channel layer
• Select (with the magic wand tool) the white, and delete it. You’ll need to repeat the select and delete for areas inside closed areas, like the area inside letters o, a, p etc.
• Save the finished work as a png or tif. Both formats support transparency, and both can be opened in Inkscape.

Then, working in Inkscape, put the transparent layer with the line art on top of the scan of the waterbody. Adjust the registration so they line up correctly, and save the finished product.