Autonomous boats without GPS

Autonomous boats have many names: roboats, unmanned surface vessels, unmanned surface vehicles and self-steering boats. It is the same thing. Autonomous robots are just a variant of autonomous robots operating on the surface of the water.

There are many use cases for autonomous boats:

  • Delivering goods and passengers
  • Navigating channels and harbors for inspections
  • Patrolling
  • Autonomously docking to larger ships, for example, after performing a rescuing operation
  • Using underwater sonars for underwater inspections and object detection

We clearly focus on autonomous boats without GPS – not on maritime boats or large vessels. The article below discusses self-steering boats working in channels, tunnels, indoor, underground – in any GNSS denied areas – not in the open sea or lakes with easy positioning and navigation using GPS.

Example of precise tracking of racing boats without GPS

How autonomous boats work

Autonomous boats like autonomous robots or self-driving cars rely on several key systems in order to be autonomous:

  • Localization
  • Obstacle detection and avoidance
  • Mobility or propulsion

Since unmanned surface vehicles interact with the world, users, and perform some useful tasks, they also has to be capable of:

  • External communication and connectivity
  • User interface
  • Payload carrying capability

Autonomous boats get tasks from the end users or operators or larger ships and perform their tasks autonomously based on the localization systems and systems of obstacle detection and avoidance. They are relying on the controllers and processors, memory and the programs to operate with the given rules. They are indeed simply a subset of autonomous robots.

Thus, like any autonomous robots, autonomous boats have sensors, processors, and actuators.

Self-steering boats are typical autonomous robots, but on the water surface.

There many other ways for localization, for example, LIDARs. But those are not recommended for the boats positioning, because:

  • Expensive
  • Don’t work well in fog or rain
LIDARs are useful for obstacle detection – not for positioning

Cameras seem to be better than LIDARs in theory. But in practice, still, robust and precise positioning purely based on cameras is very challenging to implement and their performance is heavily affected by lighting conditions, water reflections, fog, rain.

Therefore, for autonomous boats in GNSS denied areas we recommend external RTLS systems such as Marvelmind Indoor “GPS” or UWB as the main source of positioning. The best performance, as usually, is provided but a sensors fusion approach.

Problem

When GPS/GLONASS/Galileo/Beidou is available, navigation of autonomous boats is a relatively straightforward task, particularly, when some flavors of RTK GPS is available. But it is a significantly more challenging task in GPS/GNSS denied areas, for example:

  • Channels surrounded by tall buildings
  • Tunnels
  • Closed viaducts
  • Under the bridges
  • Underground

Even when GPS is available, but RTK GPS is not available, but an autonomous boat must dock to a moving ship.

Another type of problems arises when several boats must be moving in sync close to each other maintaining the distances, like swarm boats.

Solution

The solution is a real-time locating system (RTLS) or indoor positioning system (IPS), for example, Precise Indoor “GPS” by Marvelmind.

Don’t be confused with the word indoor. If it is indoor, it can work indoor AND outdoor. But the majority of outdoor navigating systems, for example, GPS, can’t work indoor, because GPS satellites’ radio signal doesn’t propagate through walls or ceiling.

How RTLS for self-steering boats work

Navigation for autonomous boats without GPS relies one of the types of real-time locating system (RTLS). Such a system doesn’t substantially differ from a similar RTLS system for autonomous robots or AGVs, for example.

The RTLS consists of three main elements:

  1. Stationary beacons (anchors) – equivalent of GPS satellites. They are used as reference coordinate points for positioning
  2. Mobile beacons installed on the boat
  3. Modem/router – a central device to control the system and to get the location data of the boat in one place – ground stations in GPS

Self-steering boats can get location data, including gyro and accelerometer data from an inertial measurement unit (IMU) directly from the mobile beacon.

Or they can be remotely controlled by an external brain getting their location and IMU data via the modem – central controller of the system. Though the self-steering boats will be remotely controlled, it doesn’t make the boats non-autonomous. They will remain autonomous. Simply their main controller will be outside of their main body.

Quick and dirty recommendations on configurations

If mobile beacons are not exposed to water or dust:

In this case, tracking of boats is not different from tracking of robots/AGVs/vehicles in 2D. Check the Robotics page for more details. In short:

  1. Starter Set Super-MP-3D – the simplest and the most versatile set to start with
  2. Starter Set Super-MP-3D + Super-Beacon – if you want Location+Direction
  3. Starter Set Super-MP-3D + Super-Beacon + 2 x Omni-Microphones – if your area is large (20x20m or more) or your stationary beacons are 30 degrees from the horizon or lower. You will be able to build robots with this kind of driving capabilities

If mobile beacons are not exposed to water or dust:

Then, the recommended configurations are exactly the same, but the mobile beacons shall be Super-Beacons-Outdoor – they are IP protected.

Customized configurations

For the most recommended configuration for your particular case with your specific requirements just send us an email to info@marvelmind.com.

Autonomous boats vs. other types of autonomous robots

Autonomous boats vs. autonomous wheeled robots/AGVs:

  • Both types operate mostly in 2D
  • There are typically more obstacles and obstruction for the wheeled robot
  • Wheeled robot has odometer as an additional source of location information
  • Water is a serious hazard for electronics – more problematic for boats. Salt water is even more dangerous

Autonomous boats vs. autonomous drones:

  • It easier for the boat, because it is 2D
  • There is typically less obstruction
  • Drones fall. Boats sinks. Still drone’s life is more dangerous and typically short
  • Boats can stay autonomous much longer than drones, because of batteries and energy supply in general

"Lie, fishing stories, election promises, statistics, and IPxx" - be realistic

Remember, that the right level of ingress protection guarantees that the devices won’t be killed with a short-time exposure to splashes of water or rain. The IPxx certificate doesn’t say anything about the prolonged exposure, or exposure to something that it is not a clean fresh water, for example, dirty, oily or salty water; or to snow, etc.

Yes, most likely the IPxx devices will survive thous exposures as well. But not guarantees. That is an open secret with all IPxx fine prints. Be aware and be realistic with expectations.

What to do?

  • Clean with fresh water after use so that dirt or salt or similar pollutants wouldn’t destroy the protective membranes
  • Make sure that ice or frost won’t puncture the membranes. Don’t let the water freeze on the beacons
  • For the long-time rain exposure use special umbrellas – similar to outdoor cameras, for example – maintain line of sight to stationary beacons
  • The outdoor beacons can withstand exposure to rain or splashes of water, but the tracking performance is not guaranteed. The devil is in detail

If anything is unclear, contact us via info@marvelmind.com