The Tampa Bay map gets more questions than anything else I make, and most of them are some version of "is that real?" It is. The relief in the navy water panel is the actual floor of the bay, pulled from a government survey and cut down to fit a 12-inch frame. Here's how it gets from a dataset to a thing you can hang on a nail, including the parts that took a few tries.
Where the depth comes from
The data is NOAA's Coastal Relief Model, the one-arc-second version. One arc-second works out to a grid cell roughly a hundred feet across, which sounds coarse until you compare it with the alternative. My first attempt used NOAA's global ETOPO grid, where each cell covers closer to a quarter mile. At that resolution the main shipping channel simply vanished. A dredged channel is only a few hundred feet wide, and a quarter-mile cell averages it into the shallows on either side, so the bay came out as one smooth bowl. At one arc-second the channel comes back as a distinct cut, the flats read as flats, and the deeper water out in the Gulf reads as deeper.
Cleaning it up for a printer
Survey data is noisy, and a 3D printer will faithfully reproduce every bit of that noise as grit on the surface. So the depths get smoothed slightly before anything is built, and the coastline gets simplified: any wiggle smaller than about a millimeter on the finished panel is dropped. At this scale a millimeter is a few hundred yards of real shoreline, which is about the limit of what your eye can read at arm's length anyway. Too much simplification and the coast turns into a cartoon; too little and the printer chokes on it. Finding that line took longer than I'd like to admit.
The bridges are the hard part
Anyone who lives here knows the bay by its bridges, so if the Skyway lands in the wrong spot the whole map is wrong, no matter how good the water looks. The Sunshine Skyway, Gandy, Howard Frankland, Courtney Campbell and Bayside bridges are traced along their real paths, and then the entire map is fitted so that all ten bridge ends (two per bridge) land where they actually touch shore. Between that and a separate pass that registers the land outline to the depth grid, the coast and the water finally agree. In early versions they disagreed by a hair everywhere, and you could see it.
The bridges are printed as separate white pieces that sit a fraction below the tops of the land, so they read as crossings over the water rather than as spits of land. The land isn't one plate either. Every island and each piece of the mainland is its own part; land and bridges together come to sixteen separate pieces, each set into the navy water panel.
What it isn't
The compass rose and scale bar are there because a chart without them looks unfinished, not because you should navigate by this. It's decorative wall art built from survey data; use a real chart on the water.
Who ends up with one
Mostly people who know the bay: boaters who can point to their favorite spot on it, and people who just moved to St. Pete or Tampa and want the place on the wall. It's a 12 × 12 frame, under a hundred dollars, and made a few miles from the water it shows. You can see the current photos and details on the Tampa Bay depth map page, and if you want a different bay, lake or stretch of coast, ask the studio; the same process works anywhere NOAA has surveyed.
If you're new to the idea, what bathymetric wall art is covers the basics, and how each piece is made explains what's inside the frame.