International Journal

on Marine Navigation

and Safety of Sea Transportation

Volume 5

Number 2

June 2011

167

1 INTRODUCTION

The International Hydrographic Organization (IHO)

is an intergovernmental consultative and technical

organization established in 1921 to support the safe-

ty of navigational, and to contribute to the protection

of the marine environment. One of its primary roles

is to establish and maintain appropriate standards to

assist in the proper and efficient use of hydrographic

data and information. (Ward et al. 2009)

This paper will describe the genesis of S-101 the

new Electronic Navigational Chart Product Specifi-

cation including its evolution from S-57 and S-52 –

“Specifications for Chart Content and Display As-

pects of ECDIS.” The primary purpose of the paper

is to communicate with the ENC user community

the activities underway at the IHO in the develop-

ment of this product specification and promote

comment and the involvement from the maritime us-

er community. The intent is not to develop S-101 in

a vacuum, but to actively solicit input from software

and equipment manufacturers and the ultimate end-

user: the mariner.

1.1 S-57

One of the primary standards that the IHO is respon-

sible for is IHO standard S-57, which is the current

IHO “Transfer Standard for Digital Hydrographic

Data.” It was formally adopted in May 1992 and

since that time it has become universally adopted as

the underpinning standard for Electronic Naviga-

tional Charts (ENCs). S-57 Edition 3.1 was “frozen”

in November 2000 and will remain so until no long-

er required. (Ward et al. 2009)

In January 2007, in response to an IMO update,

the IHO released a supplement to S-57 to include

new features and attributes required to encode Ar-

chipelagic Sea Lanes and Particularly Sensitive Sea

Areas on ENCs. One of the characteristic features

of S-57 is that the object and attribute catalogues de-

fining the content of all ENCs is an integral part of

the standard – thus a new supplement to S-57 was

required to implement these new features.

According to an information paper published by

the IHO, the following are current limitations of

S57:

− It has an inflexible maintenance regime. Any ad-

dition of new features and attributes to the soli-

tary catalogue for new products would have seri-

ous consequences for users of the ENC product

specification such as ECDIS manufacturers, data

production software vendors and regulatory au-

thorities. It would trigger continual new editions

because it freezes the object and attribute cata-

logues of the standard. Freezing the allowable

content within data standards for lengthy periods

is counter-productive for the end user.

− As presently structured, S-57 cannot support fu-

ture requirements (e.g., gridded bathymetry, or

complex time-varying information).

The New Electronic Chart Product

Specification S-101: An Overview

J. Powell

National Oceanic and Atmospheric Administration, Silver Spring, United States

ABSTRACT: The development of S-101 represents a major step forward in product specifications for Elec-

tronic Navigational Charts (ENC). Based on the IHO geospatial framework standard S-100, S-101 will be-

come the eventual replacement to S-57 ENCs. This paper will discuss the phased development approach that

will lead to an ENC with improved functionality and better data handling throughout the ENC supply chain

from producer to end-user, and will touch on several transition options that are under development.

168

− Embedding the data model within the encapsula-

tion (i.e., file format) restricts the flexibility and

capability of using a wider range of transfer

mechanisms while retaining data structure and

content.

− It is regarded by some as a limited standard fo-

cused exclusively for the production and ex-

change of ENC data.

As a result of these limitations, in 2000 the IHO

approved a major revision to S-57, resulting in the

new framework geospatial standard S-100 (Ed 1.0.0

- January 2010).

1.2 S-100

S-100 provides a contemporary hydrographic geo-

spatial data standard that can support a wide variety

of hydrographic-related digital data sources, and is

fully aligned with mainstream international geospa-

tial standards, in particular the ISO 19000 series of

geographic standards, thereby enabling the easier in-

tegration of hydrographic data and applications into

geospatial solutions such as coastal zone manage-

ment. S-100 extends the scope of the existing S-57

Hydrographic Transfer Standard. S-100 is inherently

more flexible than S-57 and makes provision for

such things as the use of imagery and gridded data

types, enhanced metadata and multiple encoding

formats. It also provides a more flexible and dynam-

ic maintenance regime for objects, attributes and

portrayal via a dedicated on-line registry.

The S-100 standard provides a framework of

components that are based on, and designed to be in-

teroperable with, the ISO 19000 series of standards

and specifications. These standards and specifica-

tions are also used as the basis for most contempo-

rary geospatial standards development activities and

are closely aligned with other standards develop-

ment initiatives such as the Open Geospatial Consor-

tium (OGC).

The IHO has also developed an associated Regis-

try to be used in conjunction with the S-100 stand-

ard. The IHO Registry contains the following addi-

tional components;

− Feature Concept Dictionary (FCD) Register.

− Portrayal Register.

− Metadata Register

− Register of data producer codes.

A particularly significant aspect of S-100 is that it

provides the framework for the development of the

next generation of ENC products, as well as other

related digital products required by the hydrograph-

ic, maritime and GIS communities.(Ward, Alexan-

der, and Greenslade, 2009) S-100 contains all the

components necessary to create conformant product

specifications to exchange a variety of digital hydro-

graphic and marine geo-spatial information. S-100

contains multiple parts that were profiled from the

ISO 19000 set of standards.

2 S-101

S-101 is the new Electronic Navigational Chart

Product specification, currently under development

by the IHO TSMAD Working Group. S-101 draws

upon the concepts of S-100 such as exchangeable

and dynamic feature and portrayal catalogues, and

richer geometric models, information types and

complex attributes. The use of these new feature

types will allow ENC producers to overcome a

number of known encoding shortcomings in S-57

based ENCs such as the overuse of caution areas,.

In addition, the improved functionality will lead to

more efficient data handling and better portrayal def-

inition within ECDIS equipment, by eliminating or

reducing the number of conditional symbology pro-

cedures.

One of the major benefits in S-101 is the ability

to introduce additional functionality that is not avail-

able in S-57 ENCs. S-101 ENCs will eventually be

the base navigation layer within an S-100 enabled

ECDIS, but the true potential will not be realized un-

til additional product specifications are developed to

interact with S-101. Currently, the IHO has ap-

proved work for S-100 based product specifications

for high resolution bathymetry and for nautical pub-

lications. Other potential S-100 based product spec-

ifications may include real-time tidal information

and port operations information. A system capable

of handling multiple S-100 products will allow for

better navigational decision making by containing

information regarding real time tides and sailing di-

rections.

The key to the successful development of S-101

is the involvement of the maritime stakeholder

community. This list includes: Hydrographic Offic-

es, production software manufacturers, ECDIS

equipment manufacturers, end-users, such as mari-

ners, port authorities, and any other interested par-

ties. During this process both TSMAD and the IHO

are engaging in a continuous dialogue with stake-

holders. In each of the past two years the IHO has

held S-101 stakeholder workshops in order to pre-

sent the status of S-101, the phased development

process, and to receive feedback and suggestions on

how best to overcome the current limitations in S-57

ENCs and the associated ECDIS portrayal require-

ments.

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2.1 Dynamic ENC Content

The biggest advantage S-101 will have over the ex-

isting S-57 ENC product specification is the intro-

duction of dynamic feature and portrayal catalogues.

The term dynamic is used to characterize continuous

change. While similar in content to the current S-57

object catalogue and the S-52 presentation library,

S-101 implements the dynamic constructs prescribed

by S-100. In S-101, the relationship between fea-

tures, attributes and enumerants are defined within a

single feature catalogue. Although, part of the stand-

ard, the feature catalogue is built through a registry

responsible for defining data content and is machine

readable, thus allowing ECDIS to easily update

onboard systems via a software update. Under the

current S-57 ENC regime updates to feature content

may take up to five years to implement through the

existing supplement process. Under S-100 the con-

tent of the registry is continuously changing, but the

S-101 Feature and Portrayal Catalogues will be ver-

sioned, enabling the IHO to take advantage of the

dynamic register content, but implementing a con-

trolled update process for the end-users.

S-101 also defines a dynamic portrayal catalogue.

This catalogue will replace the S-52 standard presen-

tation library. The portrayal catalogue is a machine

readable file containing IHO approved symbology

and look-up table instructions to properly render

ENCs on an ECDIS. This and the machine readable

feature catalogue will make S-100 based ECDIS sys-

tems truly “plug and play”.

S-101 will also make use of two new S-100 fea-

tures to enhance the encoding, transfer, and portrayal

of data. The first is a complex attribute, which has

similar characteristics to the ISO 19000 attribute of

attribute. A complex attribute is an aggregation of

other attributes, either simple or complex (Figure 1).

The second is the use of “information types”. An

information type does not have any spatial attribu-

tion and will provide information about a feature by

association. This can be used to represent a note as-

sociated with a pipeline or a buoy, for example. Un-

der S-57, chart notes are typically encoded as a Cau-

tion Area – which is an alarm feature in ECDIS.

Many of these notes contain relevant information

and the only way to convey that information is

through a Caution Area, however, most of the time

this information does not need to signal an alarm.

The creation of additional information type features

will help reduce the amount of caution areas, a

known encoding limitation within the current stand-

ard.

3 THE PHASED APPROACH TO S-101

DEVELOPMENT

In order to address the concerns of stakeholders, at

TSMAD 19 in October 2009, the membership

agreed to a four-phase approach in the development,

testing, and release of S-101. This approach will

follow the methodologies of System Development

Lifecycle Design.

The key benefits of this approach are: it allows

for iterative development, where each iteration is us-

able and testable. It also allows for controlled and

manageable change and does not try to solve every-

thing at once. A phased approach will enable stake-

holders to plan their development implementation of

S-100 and will allow the hydrographic community to

engage external stakeholders such as type approval

authorities in the new standard.

Figure 1: Example of a complex attribute for light sectors

170

3.1 Phase 1: S-57 Content Equivalent

Phase one of the development of S-101 is the “S-57

content equivalent”. During this phase the existing

feature content of S-57 is being replicated in an S-

101 based product, using S-100 as its underlying

framework.

The constraints for phase 1 are:

− The S-101 XML Feature Catalogue will be lim-

ited to only those features and attributes that are

currently in S-57

− Introduction of S-100 geometry and the utiliza-

tion of compound curves

− Use of the modified S-100 8211 encoding

− Use of complex attributes for light sectors and

structured text attributes.

The major deliverables for this phase are an ini-

tial product specification and a content equivalent

feature catalogue. The following benefits will be re-

alized from phase one development:

− Proof of Concept and validation of S-100,

− Feature Catalogue can be exchanged as data – not

specification,

− Utilization of a new 8211 encoding,

− Creation of an S-100 compliant product specifica-

tion (which can also be used as a template for

other S-100 product specifications),

− Proof that an S-57 based product can be built us-

ing S-100 mechanisms.

The last point is important as it will be the proof

of concept for the ECDIS stakeholder community

that S-101 will be similar to S-57, yet utilize the new

functionality that is provided in S-100. In doing so

it will pave the way for the development of addition-

al product specifications that will be interoperable

with S-101.

3.2 Phase 2: Enhanced Packaging and Data

Loading Mechanisms

Phase 2 of S-101 will include

− the addition of the S-101 new support file formats

and management,

− improved discovery metadata, from which EC-

DIS manufactures can inform the mariner which

notice the dataset is corrected through.

− The S-101 portrayal catalogue

− New ENC display scales matching standard radar

ranges that will be utilized for ECDIS loading.

During this phase TSMAD will also investigate

the possibility of introducing scale independent and

scale dependent data. If agreed by both TSMAD

and the associated ECDIS stakeholders, ENC pro-

ducers will be able to make the decision to partition

a set of navigational data into two separate datasets

based on whether their associated geometry is de-

pendent on the compilation scale of the chart or not.

The primary advantage of this structure is that re-

ceiving systems only need hold the scale independ-

ent features once, whereas in the current model mul-

tiple occurrences of features are required for

different display scales. This in turn effectively re-

duces the size of the ENC dataset and increases the

speed at which updates can be applied to datasets.

The deliverables for phase 2 will be an updated S-

101 product specification addressing metadata and

support file functionality, a revised feature catalogue

and the first portrayal catalogue – effectively a trans-

lation of the current S-52 standard. The anticipated

benefits from phase 2 are:

− Improved data delivery

− Improved data discovery

− Easily Accessible Metadata

− Comprehensive support for auxiliary file formats

(xhtml, jpeg)

3.3 Phase 3: Extending the Model

During phase 3 the following will be included:

− More complex attributes introduced into the fea-

ture catalogue as well as the introduction of in-

formation types.

− Support for multiple languages

− Cartographic attributes that will support text

placement, similar to a paper chart and alleviating

the current cluttered text display associated with

S-57/S-52 portrayal

− Revised guidance on pick reports enhancing bet-

ter end user experience.

The updated feature and portrayal catalogues will

allow for testing of the dynamic nature of S-101.

The expected benefits from this phase are:

− Prove dynamic updating of feature and portrayal

catalogues

− Enhanced language support

3.4 Phase 4: Scalability and Finalization

Phase 4 is the final phase in the development of S-

101. At this point the first version of the product

specification, feature catalogues and portrayal cata-

logues will be ready for approval by the IHO mem-

ber states - probably in 2013. A tentative schedule

for the entire development process is listed in Ta-

ble 1.

171

Table 1. Tentative S-101 development schedule

______________________________________________

Phase Start Date End Date

____________ _____________

MM/YYYY MM/YYYY

______________________________________________

Phase 1 01/2009 12/2010

S-57 convertor 11/2010 04/2011

Phase 2 01/2011 08/2011

Phase 3 09/2011 03/2012

Phase 4 04/2012 12/2012

_____________________________________________

4 TEST BEDS

Another important element in the development of

the S-101 product specification is the requirement

for test beds during the development lifecycle and

beyond. TSMAD has begun the process of identify-

ing items needed for the test beds. The main items

are as follows:

− S-57 to S-101 open-source convertor

− S-101 open source data editor

− S-101 open source data viewer

− S-100/101 ECDIS reference Test Bed

In recognizing the need for test beds and to help

promote the development of the S-101 Product

Specification, the National Oceanic and Atmospher-

ic Administration (NOAA) contracted with ESRI to

develop an S-57 to S-101 open source convertor.

Once completed, NOAA will turn this over to the

IHO to be placed in the public domain. This conver-

tor is intended to convert existing S-57 ENC data in-

to S-101 ENC data by utilizing the feature catalogue

developed in phase one of the project plan. It will

also utilize the new ISO8211 encoding and provide

samples of S-101 test data for interested stakehold-

ers. It is expected that this convertor will be com-

pleted in March 2011.

TSMAD has also recognized the need for both an

S-101 data editor and a viewer to enable the creation

of S-101 data from scratch. This is so the functional-

ity of the exchangeable feature and portrayal cata-

logues can be proved and to allow the creation of

test data using new S-101 functionality.

The final test bed required will, in effect, be a

reference S-100 ECDIS. It will enable TSMAD to

test the updateable feature and portrayal catalogues

in an environment that is modeled on genuine dis-

plays suitable for type approval.

5 TRANSITION

Although, S-101 is not expected to be adopted by

the IHO as a standard before at least 2013, it is not

too early to begin the process of informing the mari-

time community of the development of S-101. That

is the purpose of this paper.

One of the major issues that will need to be

agreed by the IHO and relevant stakeholders is how

to transition from S-57 ENCs to S-101 ENCs. Ob-

viously current S-57 enabled ECDIS will not be able

to view S-101 data and there will have to be a

lengthy transition period to enable both end-users,

manufacturers, ENC producing countries and regula-

tory authorities to changeover. The successful de-

velopment of S-57 to S-101 data converters will

likely play a key part in determining how quickly the

changeover could be made.

Figure 2: S-101 Test Bed

REFERENCES

Ward et al. 2009. IHO S-100: The New IHO Hydrographic

Geospatial Standard for Marine Data and Information. In-

ternational Hydrographic Organization. Monaco

S-1

00 IHO Universal Hydrographic Data Model (Ed 1.0.0 –

January 2010). International Hydrographic Organization.

Monaco

S-57 IHO Transfer Standard for Digital Hydrographic Data,

Edition 3.1 November 2000. International Hydrographic

Organization. Monaco

ISO/IEC 8211:1994: Information technology – Specification

for a data descriptive file for information interchange. In-

ternational Organization for Standardization. Geneva, Swit-

zerland.

ISO 19100 Series – Geographic information/Geomatics. Inter-

national Organization for Standardization. Geneva, Switzer-

land.