It took most of this summer to get my tide clock to predict accurately, using NOAA harmonic constituents data crammed into an Arduino, a GPS module, and published formulas.
Thanks! I'm really glad you like the LunaKron. I make a couple other versions that have less wood aesthetic and more futuristic black acrylic with a photorealistic, silvery moon.
I connect a tiny GPS module to the Arduino via 3 wires: power, ground, and serial input, and use Mikal Hart's "TinyGPSPlus" module to parse the NMEA data streams.
Putting the marker inside the tide curve would give it a cleaner look.
I considered it, and figured it was more legible to have the hour marker directly under the numbers. People looking at the NautiKron from across the room or who have low vision might like it better this way.
Good idea to revisit -- I'm always tweaking the designs and responding to owner feedback.
They're all fully automatic GPS-enabled timepieces. For a couple of years I've been developing, hand-making, and selling these clocks that track the moon phase, the sun's position, etc.
My new idea is the tide clock "NautiKron." It's getting a lot of interest from US coastal buyers.
No pics of it yet but you can see the others here: Https://digitalhorology.com