Distributed mixed reality for diving and

International Journal on Computational Sciences & Applications (IJCSA) Vol.4, No.5, October 2014
Distributed Mixed reality for diving and
underwater tasks using Remotely Operated
Vehicles
Mehdi Chouiten1,Christophe Domingues2,Jean-Yves Didier3,Samir Otmane4 and
Malik Mallem5
1IRA2 Team,IBISC Laboratory,University of Evry,France Wassa, Boulogne
Billancourt, France
2,3,4,5IRA2 Team, IBISC Laboratory,University of Evry, France
ABSTRACT
Taking advantage of state of the art underwater vehicles and current networking capabilities, the visionary
double objective of this work is to “open to people connected to the Internet, an access to ocean depths
anytime, anywhere.” Today, these people can just perceive the changing surface of the sea from the shores,
but ignore almost everything on what is hidden. If they could explore seabed and become knowledgeable,
they would get involved in finding alternative solutions for our vital terrestrial problems – pollution,
climate changes, destruction of biodiversity and exhaustion of Earth resources. The second objective is to
assist professionals of underwater world in performing their tasks by augmenting the perception of the
scene and offering automated actions such as wildlife monitoring and counting. The introduction of Mixed
Reality and Internet in aquatic activities constitutes a technological breakthrough when compared with the
status of existing related technologies. Through Internet, anyone, anywhere, at any moment will be
naturally able to dive in real-time using a Remote Operated Vehicle (ROV) in the most remarkable sites
around the world. The heart of this work is focused on Mixed Reality. The main challenge is to reach real
time display of digital video stream to web users, by mixing 3D entities (objects or pre-processed
underwater terrain surfaces), with 2D videos of live images collected in real time by a teleoperated ROV.
Categories and Subject Descriptors
D.2.11 [SOFTWARE ENGINEERING]: Software architectures—Domain specific
architectures. H.5.1
[INFORMATION INTERFACES AND PRESENTATION]: Multimedia Information
Systems—Artificial, augmented, and virtual realities. C.2.1 [NETWORK ARCHITECTURE
AND DESIGN]: Distributed networks
General Terms
Design, Experimentation
Keywords
Augmented Reality, Mixed Reality, Distributed Architecture, Underwater, Telerobotics.
DOI:10.5121/ijcsa.2014.4501 1

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1.INTRODUCTION
Oceans represent 70% of earth surface, while those who have some knowledge of oceans and seas
depths (divers and marine scientists) represent less than 0.5% of world’s population. This is not
only due to the lack of knowledge but more to distance issues for people living in outback areas
and to the cost of safe diving experience. On the other hand, even though underwater equipment
has been greatly improved, marine scientists and divers still have to perform a lot of manual
repetitive tasks that could be automated. We address this issue in our work by providing an
assisted solution to marine wildlife monitoring and by setting a framework able to support
extension to other applications. Virtual diving in real time through web teleoperation of a ROV
and Mixed Reality is a new, innovative way to discover the undersea world on-line,
complementing or replacing scuba diving, giving access to knowledge and discovery of seabed.
The challenge is to mix 3D pre-processed underwater terrain surfaces of distant sites with the
video stream provided by the ROV. ROVs are presently operated by a distant operator through an
umbilical cable. Nevertheless it appears that technologies and experience already acquired in the
field of teleoperation via internet of robots, in general, and more specifically, in the field of
operation of underwater robots is now mature enough to seriously consider the development of
ROVs teleoperation by Internet ([1], [2], [3] and [4]), which may constitute a technical and
technological breakthrough.
In addition to teleoperation as it is meant classically, the main objective of this work is to enrich
the user’s experience with reliable, real time generated, graphical and textual entities helping to
understand the situation in a relatively unfamiliar environment, to ease and speed-up decision
taking in such environment and to automate tasks such as marine animals detection and counting
in real-time and allowing to create a log for further statistical studies over time.
As an additional feature, the whole architecture is designed to be distributable on several sites.
This makes the application more flexible and allows the involvement of multiple users.
2.ROV Teleoperation
In addition to exploration applications, a lot of commercial operational tasks require to dive (ex.
underwater structure and boat hull inspection tasks, wildlife monitoring). Industry has already
tried to ease these tasks using a variety of technological and functional ways, providing the diver
with special suits, detailed seabed map and specific hardware tools.
Even if these improvements helped the divers, there still were in-situ communication problems,
no ability to automate the tasks and numerous physiological effects on the divers. Health
specialists have studied effects of working in such a high pressure, viscous and weightless
environment. Beside the disorientation and affection of tactile-kinesthetic and vestibular systems,
some serious medical issues may appear.
We can quote Nitrogen Narcosis, Pulmonary Oxygen Toxicity, decompression Sickness (DCS),
Arterial Gas Embolism (AGE), Hypothermia, Barotraumas, etc. Those are discussed in [5], [6]
and [7]. The use of ROV (Remote Operated Vehicle) allows avoiding the largest part of these
issues (especially on exploration [8] and inspection tasks [3] and [4]). In addition, the ability to
operate distantly in a human friendly environment with all necessary information from a set of
sensors also improves the speed and the quality of decisions.

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3.Augmented Reality Component System
Practically, AR applications which objective is assisting the users often share several common
components used in different ways. Due to heterogeneous input devices providing data at different
rates and due to different processing algorithms requiring different computation times, research
efforts were initiated to offer common frameworks aiming at offering flexible, reusable and
customizable components to build AR applications. These efforts have allowed the emergence of
component based AR dedicated frameworks.
Amongst the most remarkable ones, we cite Studiers tube [9]. It is based on the concept of
distributed scene graphs. Each user has a local scene graph which modifications are propagated
through the network to maintain the graph consistency.
One of the most accomplished state of the art frameworks is DWARF [10] (Distributed Wearable
Augmented Reality Framework). It is based on interdependent CORBA (Common Object Request
Broker Architecture) services. The architecture is decentralized and several applications proving
efficiency of the framework have been developed. Some other frameworks are based on the same
main concepts such as AMIRE [12] (Authoring Mixed Reality) and MORGAN [11].
The framework on which our application is built is called ARCS [14] (Augmented Reality
Component System). ARCS is a component-based framework dedicated to AR. Its components, as
classical components [15], can be configured and composed with other components. ARCS uses
the signal/slot paradigm (borrowed from user interface libraries) to connect components to each
other in order to make them communicate.
Tinmith[13], is a library written to develop mobile AR systems. The communication between
modules is made possible by client-server style architecture. A module providing data is the
server that listens to clients that request a subscription. When data on the server is changed, the
new values are sent to all clients that have registered their interest to this message. The clients can
then use the new data to perform the task of the module (e.g. refresh the display). The system is
asynchronous and data driven. If there is no new data, no new message will be generated and no
action performed by any software module.
In ARCS, every application is described as a set of threads. Basically, a finite state
machine,which states represent a specific configuration of the application’s data flow controls
each thread. Such a configuration is called a sheet and contains configuration values for
components as well as a list of signal/slot connections. Each change of state in the state machine
results in a change of global configuration of components and hence reconfigures connection
between components, that is to say the dataflow.
A simple example would be an application with one automaton (one thread), with a given number
of sheets (eg. each sheet representing a given scenario). Here, the state machine’s role would be
to switch from a scenario to another.
From the technical point of view, ARCS is written in C++ and is based on Qt Library, which
already implements the signal/slot concept. ARCS supports XML and JavaScript as scripting
languages to describe applications behavior.
The framework also supports distributed components via a specific middleware and webservices
in standard formats (XML, JSON). The performance of distributed applications based on ARCS
has been assessed with a methodology dedicated to AR distributed systems [19].

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4.ROV Teleoperation System
4.1.System architecture
The system is constituted of five main types of sites (network nodes) that are:
• ROV site (usually in the sea / pool);
• ARCS module (Mixed Reality application site);
• 3D repository site where are stored 3D content (e.g: fauna and flora models);
• Web server which hosts the web application;
• User site (can be several users on different sites).
Figure 1 illustrates the relationships and data streams exchanged between the five sites. Except
the ROV site, all the other sites may be regrouped depending on the application scenario. The
architecture has been built this way to offer more flexibility.
Figure 1. Data streams exchanged between the five sites
Basically, the system works as follows. The user controls the robot via the web user interface.
The web GUI allows high level commands that are composed of several instructions transmitted
to the ROV. The robot equipped with a set of sensors (including two cameras, but only one can is
used in our case) sends a continuous data stream to the ARCS main application, which creates the
augmented scene and sends out the final output data (video stream and other information) that is
then available to the user who can build a custom view of the scene.
The internal architecture (see figure 3) of the Web Application is divided into three parts. The
internal architecture involves as well: a web page written with HTML5, CSS 3 and JavaScript
(JS), a PHP script in order to communicate with the ROV using Modbus TCP protocol and a PHP
controller. Modbus is a serial communications protocol published in 1979. The controller is
designed to manage all data streams between modules:
• Robot instructions, which are high level commands, created by users by clicking on the
interfaces buttons (e.g. go forward, turn left, etc.). The PHP Modbus script will convert
those high level commands to Modbus commands (e.g.: ROV Address + Read/Write
code + First memory registry code + Number of bytes + Data to send + CRC16);

5
• Robot data, which are sent by the ROV (e.g. sensors status, error, etc.).
A specific module called Robot Computer Interface (RCI) permits to link the ROV to the network
(see figure 3). It is composed of four components:
• Power manager;
• Battery;
• Control and video module: convert LAN/WLAN data into RS485 data;
• Video demodulation: convert PAL/NTSC video signal into a numeric video signal.
Figure 2. Robot and Computer Interface – Electronic design
The web application can also receive data from ARCS. This is a specific data stream which
contains data computed by ARCS application in order to allow a local augmentation if many
users are viewing the live video (e.g. add sensors information on the video, build a custom view
for a custom user...). The web application will communicate with ARCS through a network
(possibly internet). ARCS will allow to mix live video from ROV with 3D contents. The 3D
contents is stored in a MySQL database. The ARCS application can also perform most of the
known computer vision state of the art algorithms (more than 150 reusable components are
available).
4.2.Web application user interface
The Web Application is written in PHP, HTML5, JavaScript and CSS3. The user interface (see
figure 4 below) is a human machine interface in order to send commands to the ROV
(teleoperation), supervise sensors data from ROV (virtual dashboard) or enable a user to interact
with other features (chat with other divers or get more information via web services, such as
weather, maps, geo-localized pictures, historical information about the area…) in the web page.
The web view is divided in six parts:
Mixed Reality live video from ARCS application;
Navigation panel to control the ROV (Moves, ROV lights, front or back cameras and Mixed
Reality On/Off switches);
HTML5 2D canvas to plot a virtual trajectory;
A chat to communicate with other users;
Data panel which displays data from ROV sensors;
Web services panel which displays or shares data from diving site.

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Figure 3. Software architecture of the web application – Data stream between modules
Figure 4. Web application – Graphical User Interface
4.3.Multimodal application user interface
The user interface of the multimodal application also permits to send commands to the ROV
(teleoperation), supervise sensors data from ROV (virtual dashboard) using natural gestures.
Users control a virtual ROV using the markers placed on the flystick device (Figure 5). Those
markers are tracked with the infrared cameras placed on both sides of the screen.
Figure 5. Hardware solution for multimodal application

This system tracks the user’s positions, so we can reproduce it on the ROV. Hence, by
manipulating a virtual ROV, the operator is controlling the real one. We also use the metaphor of
pulling a rope. Indeed, during his/her movements, the user must hold the trigger of the fly stick
pressed. When he/she releases it, the ROV stays in its last position and the user is free to move.
At the next displacement, the ROV starts from its last position and not from the user’s current
position. Therefore we do not apply directly the user's position to the one of the ROV, but we add
the movement vector performed by the user to the last position of the ROV. Users can manage the
robot’s features (camera switch, activate lights) or to show instructions for effective usage. Mixed
Reality (overlay both virtual and real worlds) is used here to help users to manipulate the distant
ROV. Indeed, assembling the different issues due to human, environment and teleoperation
factors, we observed some technical constraints (Loss of ROV maneuverability, transmission
delay/stop, etc.) affecting the application’s usage (navigation precision, safety of the robot and
spatial awareness for the diver).
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Figure 6. Multimodal application – Graphical User Interface
5.ARCS-based module
Built following the standard ARCS application pattern which itself is based on the generic
Augmented Reality application pattern introduced by Asa McWilliams [17], the application is
thought to support multiple distant users.
The architecture of the middleware that has been designed for ARCS can be found in [16].
The model of the application is data driven. Video stream coming from the ROV implies that for
each new frame processed by the video stream reader, the tracking component computes visible
3D entities and their position (3D registration). ARCS offers a framework to support several 3D
rendering engines and already supports OGRE 3D and OpenInventor. Depending on the chosen
rendering engine, the corresponding component creates then the final representation blending the
raw input with 3D contents taken from a potentially distant database. This final output is then
converted to a video stream, which is sent to the users. It is important to notice that the output
manager supports different kind of data that can be sent separately to users who will chose
different display modes and who may be interested in different textual information.
Figure 7 illustrates an example with OGRE as a rendering engine and video stream as the unique
input. We also assume in this example that the user site hosts the webserver.

The state machine is a specific component of the general application (written in XML or built via
the application designer that generates the XML description), it manages the connections between
the other components and is initialised by the profile (a configuration file containing given values
to application constants).
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Tracking World Model
Video Stream
Reader
ARCS_OGRE
Rendering
Component
Marker
file
Application
DB Site
3D
Content
Tracking
component
3D content
manager
Automaton
State machine
Context
ROV
Presentation
ROV Site
User Site
Web GUI
Output
manager
Profile
Figure 5. ARCS main application architecture (View based on McWilliams generic architecture)
As stated in the introduction, the architecture of the whole system is meant to be distributed
(figure 1). In addition, the ARCS module itself can be built as a distributed application
constituted of native ARCS components, exogenous components interfaced with ARCS, and even
external webservices (figure 8).
ARCS Engine
ARCS components collection – more than 150 are developed
Capture
Triangulation
Feature detection
Matching
Service 1 Service 2
Feature detection
Matching
Rendering
ROV StreamRead
ROV Stream
reader
Dynamically generated
webservices
ARCS dynamic application (service) description generator
ARCS JSON Parser
Service 2 interface Service description (
Component 3
Service 2 interface
ARCS JSON Serializer
ROV Video Stream
reader
ARCS Services Site
Application Site
Component 2
Virtual component
Component 1 Component 4
Figure 8. Example of an application using ARCS components as services (ARCS applications can be
accessed as services and can also use external webservices)

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6.Mixed Reality video streaming
In order to transmit the MR video over the Internet the ARCS output manager needs to digitalize
the created MR video (ROV video + 3D content). For encoding and delivering, we have chosen
Ogg format. Ogg is an open standard, open source–friendly, and unencumbered by any known
patents. Ogg is based on three technologies: a container (Ogg), a video codec (Theora) and an
audio codec (Vorbis). The output manager will stream over the Internet using the HTTP protocol
on 8080 port. This protocol is chosen to avoid firewall issues and proxy servers filtering that
usually don’t block the standard HTTP traffic necessary for people using the web.
7.Scenarios
The application being designed to be distributed and relatively generic, different scenarios have
been identified to explore the feasibility of the global solution. ARCS has already been assessed
and proved to be real time capable for state of the art AR applications. However, applications
involving network communications depend not only on the used framework but also on their
consumption of network resources.
The simplest scenario is to have a ROV that communicates with the operator site on which all the
other sites are regrouped. Here we have a unique user, and no intricate network communication.
Performance issues rely only on the operator machines capabilities depending on the kind of
application.
In the general case, each site is on a different machine and there may be several users. The only
point where serious network performance issues emerge is when having multiple user terminals.
This issue may be avoided by multicasting the output to users.
8.Applications and tests
8.1.Set-up of the teleoperation system
Tests have been performed on November 2011 at UCPA Aqua 92 diving pit at Villeneuve-la-
Garenne. Those tests were performed to detect potential waterproof sealing problems in the ROV
and also the WWW demonstrator with the use of ARCS. The ROV is wired (umbilical cable) to
its own box (see figures 9 and 10). This box permits to charge the ROV batteries and connect it to
LAN/WLAN network (for control and video). For those tests, we have set-up a local network
using a router. A computer was connected to this network. This computer (x86 based-Windows
XP)was running ARCS and the web application with the use of a local Apache server(see figure
1).
Figure 9. On the left: ROV box – On the middle: the computer used as a client and server – On the right:
the Wifi router used for the test

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Figure 10. The ROV in the UCPA Aqua 92 pit at 5 m depth
8.2.Mixed Reality with ARCS
Real-time scene augmentation has been performed following three custom scenarios. First is
contextual scene augmenting (figure 11), that only consists in adding virtual entities for
immersive and decorative goals (ex. Adding specific species of fish depending on the
environment or adding virtual funny fish in a swimming pool, etc.).
The second test is based on marker tracking (ex. Display information on a marked zone or object
such as a pipe or a wreck).
Figure 11. Markerless contextual augmentation
In our example (figure 12), those markers are set on buoys. Applications such as collaborative
treasure hunting game and virtual fish encyclopedia have been developed (Figure 13). This virtual
encyclopedia provides 3D models of fish, and information from a database such as name, natural
environment and zones of the world where it can be found. Other information such as maximum
size, maximum depth, etc. are available in the database and can also be displayed. One can easily
build new applications with very little effort of development since ARCS offers great reusability
of components and parametrisation ability. The third and last one is based on natural features
tracking (ex. Automatic fish classification). A preliminary test has been made with the SURF [18]
(Speeded-Up Robust Features) component of ARCS (which is based on OpenSURF library), but
a more complex application is being built based on several descriptors.

Figure 12. Marker based approach. It’s used to display animated entertainment content in the UCPA aqua
11
92 pool
Figure 13. Marker-based pedagogical purpose application
8.3.ROV Localization
The location of the ROV's camera position and orientation in real time can be done using several
methods. These methods are based on the knowledge of the intrinsic camera parameters, as we
suppose that the extrinsic parameters that constitute the pose of the camera may change over time.
The principle of these methods is to use markers (or coded targets) in the real world to calculate
the camera’s position and orientation. In this case, instead of trying to directly recognise the
objects in the real world, we can only recognise those different markers placed in specific
locations in the diving site (see Figure 14). These markers are recognised by the ROV's camera
while exploring the diving path, using algorithms of the MR module.
Figure 14. Localization system using 2D markers

International Journal on Computational Sciences & Applications (I
8.4.Marine wildlife monitoring
IJCSA) Vol.4, No.5, October 2014
One other application, proving the abilities of our architecture to support state of the art com
computer
vision algorithms is the Tethys Project. Its objective is to detect marine animals and specifically
fish in real time. The application is composed of distinct components allowing different uses.
After acquiring the video stream from a stream reader
15), one of the most important components of the application is the fish detector. It is based on
regions of interest detection algorithms taking in consideration colors, texture and shape of the
region of interest. A basic non refined blob detection is shown in Figure 16.
Figure 15. Marine wildlife application: Test image
The second step is to refine the results with morphology algorithms (erode or dilate and then
smooth) and eliminate irrelevant detected
characteristics of the fish to detect (color, size…) as shown in figure 13. Then, for classification
and identification purposes, each region of interest is described with a features vector including
statistical moments of the shape, color information extracted from the color histogram and texture
descriptors.
Figure 16. Marine wildlife application: Detected regions of interest
.(a result similar to what is shown in figure
est. regions. The user can also define specific
oments JCSA) 12

13
Figure 17. Marine wildlife application: example of specific detection (reddish colored fish)
The shape descriptors are usual blob descriptors (centroid, area, elongation, and statistical
moments). Color descriptors are also based on statistical moments. For texture descriptors,
several options have been studied. Haar-like features being very sensitive to rotation, we decided
to combine statistical properties with spectral and structural texture analysis methods.
The feature vector is then matched with the features vectors in the known fish database (the
application has been tested only with 3 different species at the moment). A score is then
computed and if it satisfies a minimal threshold, the detected fish is identified as a member of a
specific species.
This application is still in development and it still needs implementation of some of the feature
descriptors and validation with a dataset of decent size.
The final goal is to identify fish and augment the scene with in real time with information about
the identified fish using any distant tablet or even smartphone with access to Internet. Within this
project, a special device has also been developed to visualise augmented reality contents
underwater [20].
9.Conclusion and Future work
We have specified and built a customizable software and network architecture in order to enable
enriched teleoperation of a ROV involving a wide variety of Mixed Reality content and computer
vision applications. Augmented scene is computed on a distant site using any relevant ARCS-based
application. This makes the system more flexible and allows the involvement of multiple
users. We have set-up three scenarios. The first was to augment the distant scene by adding 3D
content for decorative purpose. The second scenario is a marker based approach. And finally, a
complex scenario based on natural features (fish classification). The three previously described
applications are only to illustrate a proof of concept. The possible applications are very numerous.
There are way more scenarios to develop. As an example, one useful and interesting application
is the 3D reconstruction that we are working on. We already explored this research area using a
monocular SLAM (Simultaneous Localization And Mapping) approach providing valuable
feedback indoors. Taking advantage on the ARCS decentralised hybrid architecture [14], a
collaborative multi-robot and multi-sensor (including sonar-based approach) will be explored for
real-time 3D reconstruction of seabed and submarine natural environments. We are also
investigating the use of VR devices as optical tracking and haptic devices to control more easily
and feel the remote ROV.

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10.Acknowledgements
Some parts of the work described in this article are made for the Digital Ocean Project (FP7
262160) which is a collaborative project funded through European Community's Framework
Program FP7.
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