For an upcoming expedition we need to survey relatively shallow waters and coastline. Parts of the coast are too shallow to use even a small ROV like the OpenROV or even to snorkel - so we needed a vehicle with a shallow draft that would also be stable enough to handle small waves.
There are, admittedly, quite a few autonomous marine vehicles around at the moment. A lot of them are very expensive and out of reach of small organisations and individuals. Some are a lot cheaper, but are aimed at ocean crossings or long journeys where large waves and the threat of being overturned mean that a deep draft or keel are required.
We needed something with a shallow draft that was capable of hugging the coast.
There are a lot of Kayaks available specifically designed to handle different types of water - from flat bottomed white-water kayaks that are capable of turning sharply, through to longer sea kayaks more suited to travelling in long straight lines quickly.
Because of the popularity of kayaking as a hobby, there are a lot of older, end of life, kayaks available to purchase cheaply on places like Facebook and eBay.
As we aren't concerned with the condition of the seats or outfitting, then we can pick up perfectly capable Kayaks that others might not consider.
Why Raspberry Pi?
The Raspberry Pi is an extremely low cost, yet very capable computer - the Raspberry Pi Zero even more so. A lot of people already own at least one, and schools tend to own a few for educational use.
It made sense to use something that a lot of people would be familiar with. Whilst there are existing autopilot boards available, some of them open source, for a lot of sensor recording and reading - a Pi or similar would be needed anyway.
Not all waterways are the same, and not all survey missions have the same conditions. Sometimes you may need something that can keep a straight line easily, other times something that can turn quickly to get around a rocky coastline.
By keeping all of the electronics in a self-contained unit, we hope to be able to simply swap the body of Julius to best suit the surveys that need to be done.
Placing him in a 13-15 foot long sea kayak with a skeg will help with long straight line surveys, but remove the ability to make tight turns.
Wheras placing him in a 6 foot white water kayak means that he will be able to turn very quickly to follow a winding or rocky coastline, but not have as much straight line speed or be able to handle larger waves.
To the best of our ability, everything we use, write or build will be open sourced. By the end of this project we aim to have a detailed Bill of Materials, designs for new hardware and assembly instructions so that anyone interested will be able to build, and hopefully improve on, the Julius system.