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1 INTRODUCTION

Collecting data for nautical charts is one of the basic

tasks of national hydrographic organizations (HOs).

Data are being collected by hydrographic survey that

is standardized in terms of methodology and

requirements for accuracy and reliability of collected

data. Standards are international and national.

International standards for hydrographic survey are

issued by IHO, while the national ones are issued by

HOs. National standards for the accuracy and

reliability of data should be equal to or rigorous than

international ones. The collection of data for the

production of nautical charts is possible only by

hydrographic survey, while their verification and

updating can be done by some auxiliary methods.

International and national standards of hydrographic

survey are necessary in order to achieve the

maximum possible uniformity in the production of

nautical charts used in international and national

navigation. Nowadays we can say that relatively good

results have been achieved at the level of

hydrographic survey standardization. Nevertheless, a

relatively large part of the world's sea is not

adequately surveyed in line with current standards.

Data on surveyed areas vary depending on the source

and range from 1 to 15% [11], while other depth data

on nautical charts were largely estimated. For this

reason, the data on depths shown on nautical charts

are not reliable enough in certain parts of the world

sea. An interesting fact is that the distance between

two adjacent depths on nautical charts is about 10

kilometers for more than half of the world's sea [21],

while more than 80% of the oceans floor is still not

mapped even at a resolution of 1km using the echo

sounding method [14]. Although HOs make great

Analysis of Crowdsourced Bathymetry Concept and It's

otential Implications on Safety of Navigation

. Pavić & J. Kasum

University of Split, Split, Croatia

. Mišković

Croatian Military Academy, Split, Croatia

. Alujević

Croatian Navy, Split, Croatia

ABSTRACT: Crowdsourced bathymetry (CSB) is relatively new concept of collecting bathymetric data. CSB can

be defined as the collection and sharing of depth data (and metadata) measured and collected by non-

traditional survey vessels equipped with navigation instruments, while maintaining their usual operations at

sea. International Hydrographic Organization (IHO) has developed Guidance on CSB. This document provides

framework for data collection, processing and information about data uncertainty. IHO has also developed

model within CSB concept in order to make standardization of CSB data. The data collected using CSB may

represent valuable supplement to the existing data collected by hydrographic survey. Despite this fact it is

necessary to emphasize that CSB data cannot be used as official data. CSB data collection has also potential

legal issues due to the character of sounding passage within territorial and internal waters of coastal states. This

paper emphasized the differences between hydrographic survey and CSB. Advantages and disadvantages are

analyzed with it's potential implication on safety of navigation. Due to the CSB data collection model

limitations, development of bathymetric data collection model on national level is recommended.

http://www.transnav.eu

the

International Journal

on Marine Navigation

and Safety of Sea Transportation

Volume 14

Num

ber 3

September 2020

DOI:

10.12716/1001.14.03.21

682

efforts in performing the hydrographic survey it will

take a long time for the survey to be done in

accordance with the applicable standards. Therefore,

the IHO pointed to the need to introduce a new

concept of bathymetric data collection, which is based

on the use of other data sources than official ones. At

the 5th Extraordinary Hydrographic Conference 2014,

the IHO established a Crowdsourced Bathymetry

Working Group (CSBWG) tasked with developing

guidelines for collecting bathymetric data from public

sources, ie, from ships using standard echo-sounders

for navigation and positioning systems. [11].

Companies that produce electronic chart systems (eg,

Olex, Navionics, Garmin, Lowrance, Survice, etc.),

companies that create their own databases (eg, Active

Captain) and other voluntary organizations (SeaID,

TeamSurv, OpenSeaMap) are also engaged in

collecting data from public sources.[4, 19]. These

companies and organizations have their own CSB-

related protocols. The collection of bathymetric data

by the CSB cannot replace the hydrographic survey,

but this concept is a complement to the hydrographic

survey. Its main advantage is the fact that collection of

bathymetric data can be done by using any type of

vessel. The fundamental disadvantage is the fact that

the CSB cannot replace the hydrographic survey. The

paper analyzes the role of IHO in the development of

the CSB concept, legal problems that arise due to the

collection of bathymetric data and the possibility of

applying this data in order to increase safety of

navigation at the global and national level with

special emphasis on the development of the national

CSB model.

2 IHO CSB CONCEPT DEVELOPMENT

The IHO has developed the CSB concept with the aim

of increasing the amount of seabed data collected, in

order to improve seabed mapping. Since the term CSB

derives from the term "crowdsourcing", it means that

it is addressed to a large number of persons, ie ships

that can collect bathymetric data. In this way, it is

possible to collect a relatively large number of

bathymetric data in a relatively short time, all at low

cost. These facts, together with the limitations of

hydrographic survey, led to the development of the

IHO CSB concept. The IHO CSBWG has developed

the publication Guidance on Crowdsourced

Bathymetry, which defines the concept, equipment,

methodology, format and uncertainty of data

collection, processing and storage. [8, 23]. It should be

noted that this publication provides a framework for

the CSB and it is neither authoritative nor binding,

but has the character of guidelines: The IHO CSB

concept is based on the Trusted Node model

(Figure1).

Source: Authors (in accordance with [8])

Figure 1. CSB data flow through Trusted Node model

According to the model, bathymetric data can be

collected by any type of ship (e.g., passenger, cargo,

public, fishing, pleasure boats, etc.). Data are collected

voluntarily during navigation, or during other regular

ship activities. In doing so, ships use navigation echo-

sounders (usually single beam – SBES) for data

collection, while they use Global Navigation Satellite

System (GNSS) for positioning. The collected data are

submitted to the Trusted Node. Trusted Nodes are

organizations or individuals that serve as a liaison

between ships and the IHO Data Center for Digital

Bathymetry (IHO DCDB). In accordance with IHO B-

12 Trusted Node performs tasks and assist the

mariner by supplying data logging equipment,

providing technical support to vessels and

downloading data from data loggers [8]. The IHO

DCDB works with each individual Trusted Node to

standardize the data and metadata that will be

included in the database. The IHO DCDB assigns

unique keys for data authentication to each individual

Trusted Node. Authentication is performed to ensure

data integrity and an appropriate level of anonymity

of data sources [8]. Bathymetric data collected from

ships are provided to Trusted Node. The IHO

recommends that Trusted Node verify the data,

calculate uncertainty, and correct the data. After

verification and processing, the data is stored in the

IHO DCDB. This information is available to the public

online via interactive web map services for various

purposes related to seabed mapping [10]. Simply put,

the concept of IHO CSB means that data can be

collected by anyone and made available to anyone.

3 CSB DATA AVAILABILITY

The IHO established the DCDB in 1990 [9] as a global

database of bathymetric data for the development of

General Bathymetric Chart of the Oceans (GEBCO).

IHO DCDB is hosted by U.S. National Oceanic and

Atmospheric Administration (NOAA) National

Centers for Environmental Information [9, 17]. Data

are publicly available using the IHO DCDB Data

Viewer (Figure 2). The interactive menu map provides

access to data obtained using SBES, multibeam echo-

sounders (MBES), surveys conducted by NOAA, and

data obtained via CSB. Analysis of the IHO DCDB

interactive map shows that there is a relatively large

amount of data obtained from single beam and

multibeam surveys, while the amount of data

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obtained through the CSB is relatively small and

mostly data from the east and west coasts of the

United States. It is interesting to note that in the

Mediterranean Sea, only one measurement from the

CSB is currently included in the IHO DCDB.

Source: The IHO Data Center for Digital Bathymetry (tracks

in green belongs to the GEBCO Project, other tracks are CSB

Data)

Figure 2. Part of IHO DCDB interactive map

Currently, the IHO DCDB contains more than 117

million bathymetric data [17]. The number of

bathymetric data is very small in relation to the total

area of the world's oceans. It is assumed that over

time there will be a development of the CSB, which

will result in an increase in the number of these data.

4 CSB TECHNICAL REQUIREMENTS

The CSB is not a fully standardized bathymetric data

collection process, such as hydrographic survey.

Nevertheless, in publication B-12, the IHO set out the

basic principles relating to the CSB. Vessels

participating in voluntary CSB data collection should

be equipped with a GNSS for positioning and a SBES

for depth measurement. These equipment must meet

the requirements of Chapter V (Regulation 19.2.1.6

and 19.2.3.1) of the International Convention for the

Safety of Life at Sea [13]. The equipment must meet

IMO Recommendations on performance standards so

that ships have the ability to collect bathymetric data

(along with position and time) of standardized

reliability. Data from GNSS and SBES on ships are

transferred in the National Marine Electronics

Association (NMEA) 0183 standard protocol [8]. The

collected data must be stored on board. Data storage

is done using a data logger (which is delivered by

Trusted Node to the ship) or some other media on

board. The stored data is transferred from the ship to

the Trusted Node. The mode of data transfer in IHO

Publication B-12 is not strictly defined. This

publication sets out the principles of simplicity and

economy of data transfer, while the precise method is

defined between each individual Trusted Node and

the ship that collects data. [8]. In order to achieve the

required level of standardization, the IHO DCDB

accepts bathymetric data in certain (default) formats.

These formats are GeoJson, CSV or XYZT format.

The XYZ format contains longitude, latitude, and

depth. Since the depth at the same position changes

over time depending on the sea level, it is also

necessary to have time data (T). In this way, the user

of the measured bathymetric data can correct them at

the time of measurement. Therefore, bathymetric data

must be in XYZT format. For ships whose draught

changes significantly, there should be the possibility

of entering draught data (together with date and

time). Due to the vertical distance between the

waterline and the position of the echo-sounder

transducer draught can have a significant impact on

depth measurement. The IHO also recommends

automatically integrating or recording vertical and

horizontal sensors offset into the data. When

recording sensor offsets, seafarers provide this

information to Trusted Nodes. By applying these

principles, CSB is standardized because it can only

come from Trusted Node and in valid file types. The

data collected in this way have a certain value in a

whole range of activities related to the improvement

of seabed mapping.

5 CSB LEGAL PROBLEMS

CSB in its nature represents the collection of

bathymetric data, i.e., the measurement of sea depth.

Measuring the sea depth from ships is subject to

restrictions, except for navigation purposes.

Restrictions depend on the legal regime of maritime

areas. The legal regime of maritime areas is defined

by the provisions of the United Nations Convention

on the Law of the Seas (UNCLOS). According to the

provisions of UNCLOS, the level of rights of coastal

states decreases with distance from the coast. Internal

waters are under the sovereignty of the coastal state

as well as its mainland [16], therefore, any depth

measurement, except for navigational purposes, may

be considered prohibited. In the area of the territorial

seas, a foreign ship "carrying out research or survey

activities" violates the right of innocent passage in

accordance with the provision of Article 19.2 (j) of

UNCLOS [18]. In the straits, research or survey

activities shall be considered a violation of the right of

transit passage in accordance with the provision of

Article 40 of UNCLOS [18]. In the Exclusive Economic

Zone, the coastal state shall have sovereign rights and

jurisdiction over marine exploration in accordance

with the provision of Article 58.1 (a and b) of

UNCLOS. In the High Seas, all states have the right to

scientific research in accordance with the provision of

Article 87 of UNCLOS. According to the current

definition of CSB, coastal states have the right to

impose restrictions on the collection of bathymetric

data within CSBs in maritime areas in which they

have sovereignty, sovereign rights and jurisdiction.

UNCLOS recognizes neither the term CSB nor the

term “passage sounding,” which IHO links to CSB in

Publication B-12. The IHO recommends that the CSB

can be considered equivalent to other voluntary

environmental data collection initiatives, which are

intended to be used for the common good. [8]. If the

coastal state interprets CSB as scientific research, then

CSB can be considered permissible only in the high

seas. However, coastal states may allow (with

restrictions) CSBs within maritime areas under

sovereignty, sovereign rights and jurisdiction. The

solution to these legal problems can be a clearer

684

definition of the CSB in order to eliminate issues with

the provisions of UNCLOS [15] with the aim of

resolving possible political or security problems for

coastal states. Because the data collected is publicly

available in the IHO DCDB, certain legal problems

may arise there as well. These problems may relate to

publicly available data, their redistribution, and

reliability. Therefore, the IHO in Publication B-12 has

fenced off in such a way that all participants in the

CSB need to be aware of the conditions of the

licensing regime under which the bathymetric data

will be made available [8]. In this sense, the IHO CSB

Program operates under the Creative Commons

licensing framework. The IHO also stressed that every

user should use the data in good faith, taking into

account the fact of the nature and the uncertainty of

the data [8]. Furthermore, the data user must list the

IHO DCDB as the data source, and indicate if he has

made any changes to that data. Thus, the IHO

assumes no legal responsibility for either the

collection or the use of CSB data. In order to, in some

way, solve the mentioned legal problems, IHO

envisaged ‘’filter’’ in its concept of CSB data flow.

This filter refers to the collection and availability of

the collected data. Coastal states, i.e., their HOs have

the option of setting limits on the collection and

disclosure of CSB data. The IHO filter is based on the

right of coastal states to accept in full, accept with

caveats or not to accept CSB in national waters of

jurisdiction. The same principle applies to the

availability of CSB data in the IHO DCDB [12, 8].

Thus, coastal state must give explicit consent to the

collection and publication of CSB data in waters

under national jurisdiction. In Circular letter 11/2019,

the IHO called on member states to comment on the

acceptance of CSB in national waters of jurisdiction.

So far, only 15 states have given their consent to

CSBs in these waters, of which only the United States

has given unrestricted consent in all waters [7].

6 APPLICATION OF CSB DATA

Although CSB data have certain shortcomings they

can be used for a whole range of offshore activities.

Since CSB data has the character of unofficial data,

they can be applied to:

− Support in different initiatives connected with

seabed activities,

− Support in different scientific studies,

− Supplemental data for safety of navigation,

− Support in coverage the sea areas with not

sufficient, not adequate or no data existence,

− Help to prioritize survey areas by HOs,

− Determination of survey priorities and

− Determination of charts adequacy.

Currently, a number of initiatives have been

developed around the world aimed at developing

programs and projects that encourage seabed

exploration. These initiatives can be global or

regional level. CSB data can make a significant

contribution to the implementation of these projects.

The possibility of using CSB data in order to increase

navigation safety is analyzed below.

6.1 Application of the CSB in increasing navigation

safety at global level

Regarding the application of the CSB concept in

navigation safety, there is currently no publicly

available comprehensive research. Possible reasons

are unofficial nature of this data and the fact that this

is a relatively new concept. Although IHO and HOs

point out that a relatively large amount of data on

charts was collected using old positioning and depth

measurement systems, there is still no way to include

CSB data in the information content of nautical charts.

Today's positioning and depth measurement systems

on ships are more reliable than the systems used by

hydrographic ships before the advent of GNSS and

SBES. Obviously, data collected through the CSB are

more reliable than a relatively large amount of official

data. According to Baxter CSB data meet the

requirements of 1b and 2 Order of 5th Edition of IHO

standards for hydrographic surveys (IHO S-44). He

also concluded that the analyzed data meet the IHO

S-57 Category Zone of Confidence (CATZOC) Class

C, although there are elements for both Class A1 and

A2 (but the CSB data are not considered satisfactory

as it is not a systematic hydrographic survey) [2].

Despite to these facts, CSB data cannot be included in

electronic navigational charts (ENC), because ENC is

an official database created by a national

hydrographic office for use with Electronic Chart

Display Information System. [22]. Although the data

are unofficial, their use could find application in

increasing navigation safety. The use of CSB data can

potentially detect new dangerous objects on

waterways. Furthermore, by identifying significant

deviations of existing official data on nautical charts

from CSB data can have a significant impact on the

safety of navigation in the area of Special and 1a

Order of hydrographic survey. Using the data, it is

possible to determine and display in more detail the

relief of the seabed in areas with low data density.

Certainly, the use of CSB data contributes to a better

situational awareness of seabed relief in areas that are

not adequate or not measured at all. These examples

of applications are possible both globally and

nationally. However, one should take into account the

fact that currently only 15 countries are included in

the CSB concept. The reason for this should be sought

in the fact of confidentiality of hydrographic data,

vagueness of legal concept, relatively small number of

hydrographic vessels and limited resources of HOs. In

order to expand the application of the CSB concept in

national waters of jurisdiction, a model of application

at the national level is proposed below.

6.2 Application of the CSB in increasing navigation

safety on national level

Figure 3 shows a proposal for a model for applying

the CSB concept in national waters of jurisdiction. In

order to meet the preconditions for the application of

the proposed model, it is necessary to define the legal

framework at the coastal state level. Given the fact

that HOs have a relatively small number of

hydrographic vessels in relation to the sea area for

which they are responsible, it is proposed to hire

public and commercial ships flying the coastal state

flag to implement the CSB concept. In this way, the

number of vessels engaged in data collection would

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be multiplied by the CSB concept. Public and

commercial ships would send the collected data on

the principle of the CSB concept according to the

appropriate Trusted Node. Trusted Node would

verify data according to the same principles as

specified in the IHO CSB concept. At the national

level, it is possible to organize the Trusted Nodes

system in the relevant ministries or within the HO.

Public or commercial ships would collect data on the

principle of the CSB concept as part of their voyage,

or usual operations at sea. Trusted Nodes sends the

collected and verified data to the national HO, which

consolidates them into a national database and, on

behalf of the coastal state, filters the data which will

be sent to the IHO DCDB.

Source: Authors

Figure 3: Model of application of CSB in national waters of

jurisdictions

The proposed model has a general character. At

the particular level of application, variations adapted

to the organizational structure of each coastal state are

possible. Applying this model significantly increases

the number of ships participating in data collection.

7 CONCLUSION

The IHO has developed the CSB concept with the aim

of increasing the amount of sea depth data. The

concept is based on crowdsourcing which means that

a large number of ships can participate in the data

collection. The condition for participation is the

possession of GNSS and SBES and a data logger

device provided by Trusted Node. GNSS and SBES

should meet IMO recommendations on performance

standards. Data is delivered to Trusted Node via the

NMEA standard protocol. Trusted Node verifies the

data and forwards it to the IHO DCDB. The IHO

DCDB accepts data in GeoJson, CSV or XYZT format.

The data was publicly used in the IHO DCDB data

viewer. This means that the data is available to the

user at any time. This concept also has legal issues

related to the collection and publicly available data.

Data collection is primarily carried out on the high

seas and secondarily in national waters of jurisdiction

with the express approval of the coastal state.

Approval information is available on the IHO

website. As a possible solution to legal problems, the

IHO has provided filters that can protect coastal states

from collecting and publishing data in national waters

of jurisdiction. In this way, relatively large areas of

the World Seas may remain outside the IHO CSB

concept. Therefore, a national CSB model is proposed

that envisages the use of governmental and public

ships of the coastal state. This significantly increases

the ability of coastal states to collect data in national

waters of jurisdiction which has a direct impact on

navigation safety. From the examples of possible

application of CSB data, it can be seen that they can

relate to increasing navigation safety primarily as

additional data, and secondarily as basic data in

marine areas where there are insufficient, inadequate

or no official data obtained by hydrographic survey.

In this sense, these data can be used to determine the

adequacy of nautical charts and as an efficient tool to

HO in determining priorities for performing a new

hydrographic survey or re-survey in some areas with

data deficiency. Despite all the advantages of this

concept, it is necessary to emphasize once again that

these data have an unofficial character.

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