The Frauenhofer IOSB boat uses cameras to measure the exact dimensions of a lake.

Relying on the right map

(Semi-)Autonomous surface and underwater mapping for rivers and lakes

Up-to-date and accurate maps of the waterways are a prerequisite for safe and efficient shipping traffic in Germany. Authorities such as the Federal Maritime and Hydrographic Agency, but also private port operators, are obliged to provide these in an up-to-date form at all times. The main reason for this is to avoid accidents caused by an incorrect or outdated card. It deals with the classification of federal waterways, their length in kilometers, existing locks, lifting and barrages, other surrounding waters, places and borders. Currently, mapping is carried out by conventional ships with trained personnel, which is time-consuming and expensive. This can result in long intervals between measurements at a particular location.

(Semi-)automated monitoring of waterways by autonomous platforms with obstacle avoidance and traffic detection could optimize this process and provide maps in less time. As part of a three-year in-house research project, the Fraunhofer Institute of Optronics, System Technologies and Image Exploitation IOSB has developed an autonomous surface vehicle that is capable of autonomously surveying bodies of water. For this purpose, the river bed is recorded using sonar. Furthermore the bank areas and surface structures are monitored by an optical system with two integrated industrial cameras from IDS Imaging Development Systems GmbH. The information obtained in this way is then merged and transferred to a 3D map of the surroundings.

Application

The precise surveying of water bodies is a challenging task. TAPS, the Fraunhofer IOSB's semi-automatic direction finding system for rivers and lakes is able to perform this both under and above water. The vehicle, which measures approximately 2 x 1.5 x 1 meters, travels along the relevant waterway and automatically avoids obstacles, whether stationary or moving. At a speed of 2 knots - which corresponds to around 3.7 kilometers per hour - such a mission can last up to 20 hours. For visual mapping of the shore areas, TAPS has two cameras attached to a mast, each facing starboard and port, with no overlapping fields of view. Due to their high resolution, they allow a visual inspection of relevant infrastructure, such as quay walls, as well as 3D modeling of the shore area based on the recorded image data.

"We use an automatic system for intelligent image capture. As soon as one or both cameras are pointed at a predefined area of interest, image recording is started. The vehicle's own movement is also used to store only image data that is recorded from different angles and therefore offers added value in terms of content," explains Boitumelo Ruf, an expert in photogrammetry in the Autonomous Robot Systems research group at Fraunhofer IOSB. GNSS (Global Navigation Satellite Systems, such as GPS) and IMU (Inertial Measurement Unit for position determination) data serve as the basis for determining the position and orientation of the TAPS platform. "When the images are captured, they are enriched with the current GNSS position data. The latter are needed later for the assignment of precise coordinates," Ruf continues.

Result model of a shore area with crane
3D model of a surface structure
Sketch showing how TAPS autonomously circumnavigates a leaking inflatable boat.
The watercraft autonomously circumnavigates an inflatable boat.

After data acquisition, the recorded images are transmitted together with the GNSS data to a ground control station, where a photogrammetric reconstruction is carried out. Boitumelo Ruf describes the procedure in more detail: "Among other things, we use the COLMAP photogrammetric toolbox. It uses outstanding image features to first compare the input images, calculate their relative positions and create a true-to-life 3D model of the environment. We then use the tool to match the images pixel by pixel, i.e. we search for corresponding pixels and merge them exactly. The result is a dense 3D point cloud that is georeferenced using the GNSS positions, i.e. provided with the corresponding current coordinates." The 3D model can then be used for other tasks, such as visual inspections or bank monitoring.

Robust industrial cameras defy wind and weather

On the camera side, the Fraunhofer Institute relies on two uEye FA industrial cameras from IDS. The robust and resilient models with PoE are ideal for demanding environments. The camera housing, lens tubes and the screw-on connectors meet the requirements of protection class IP65/67 and are therefore optimally protected against dirt, dust and splash water.

Two IDS cameras mounted on a pole
TAPS has two uEye FA industrial cameras from IDS mounted on a mast to visually map the shoreline areas

The model used has the large-format 1.1" CMOS sensor IMX304 from Sony and delivers very clear, noise-free images with a resolution of 4096 x 3000 pixels. Thanks to its remarkable dynamic range and very high sensitivity, the global shutter sensor of the second pixel generation of the Pregius series is particularly suitable for applications in metrology, among others.

It was precisely these characteristics that were decisive for Fraunhofer IOSB's choice of camera. In addition to robustness and weather protection, important requirements for the cameras included a compact form factor and high image resolution to enable detailed visual inspections. The sensor should also offer a high dynamic range in order to capture images with a high level of detail in both sunny and shady areas. Integration via the standard GigE Vision interface enables the development and use of one driver for several systems with different cameras.

"The camera used delivers very clear, noise-free images. The sensor has a remarkable dynamic range and a very high sensitivity. It was precisely these characteristics that were decisive for our choice of camera."

— Boitumelo Ruf, expert in photogrammetry in the Autonomous Robotic Systems research group at Fraunhofer IOSB —

Outlook

The shortage of skilled workers is also a major issue in waterway surveying. Automated mapping of the waterways could not only reduce costs but also the time and, above all, personnel required. The aim of the TAPS project was to develop a prototype for this task and to demonstrate its potential in relevant scenarios. As a research institution, Fraunhofer typically develops technologies up to a level at which the functionality and suitability of the system have been proven. The next step is now cooperation with industrial partners. Dr. Janko Petereit, head of the Autonomous Robot Systems research group at Fraunhofer IOSB, explains: "We are actively looking for partners to take this final step towards commercialization together. In view of the positive results of our initial tests and the increasing demand for accurate, up-to-date waterway maps, we expect strong demand for our technology in the coming years. The knowledge gained can be used in a variety of ways. Autonomous watercraft can be used to transport people and goods by sea or inland waterways. The excavation of waterways and the autonomous surveying of fairways are also conceivable."

The project demonstrates the high potential of the interaction between robot systems and digital image processing. There might be totally new ways for surveying of shallow waters in the future, especially with regard to visual environment detection and scene interpretation.

uEye FA - the most robust and resistant industrial camera

uEye FA - the most robust and resistant industrial camera with PoE

Model used: GV-5200FA
Camera family: uEye FA

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