About us
It started with press-on nails.
The technique Caudal uses to measure a fish was built to measure fingernails.
A quarter and some algebra
“I’ve run a small custom press-on nail art business. To size customers’ nails remotely, I used a simple way to calculate real measurements from a photograph. I’d have a client photograph each of their fingertips over a quarter for scale, send me the pictures, and then I’d use a ruler over their photograph and my own quarter and some algebra to estimate how wide their nails are. It works pretty well!”
“I’m a Girls Who Code alum, and after finishing their AI coding course I decided to see if I could apply the same technique to another passion of mine, fly fishing.”
— Elsa Anderson, co-founder
From fingertips to fish
The quarter became a wallet card. The fingertip became a whole hand.
Caudal scans a photo of your whole hand next to any wallet-size card — a shopper card, a hotel key, the back of a driver’s license. They are all the same size, to the millimeter, which is what makes them work as a reference.
That measures your hand once — 22 separate distances across it: every bone in every finger, the spans between your knuckles, and your wrist to each knuckle. Caudal calibrates both hands, so it has more than forty measurements of yours to work from. They stay on your phone and are never uploaded.
From then on your hand is the ruler, and there is no card and no calibration to think about again.
What it does now
Length, weight and species, from one photo.
With her brother Ian, an engineering student at Duke, Elsa adapted the technique for fish. Caudal measures the fish against your calibrated hand, estimates its weight, and identifies the species — all from a single photo, and all on your phone.
The point is the time it saves. Nobody has to hold a fish out of the water while someone hunts for a tape measure or a scale. Take the photo, get it back in the water, read the numbers afterwards.
It was tested the unglamorous way first: hundreds of photos of Elsa’s parents holding foam fish ordered off Amazon, and then, once the numbers held up, on real fish on the water.
Measure fast, release faster.
We built Caudal for the catch-and-release angler and the conservation-minded fishery. Its core measurement methods are patent-pending.
Caudal is made by Phalanx Fishing LLC.
