International Journal
on Marine Navigation
and Safety of Sea Transportation
Volume 5
Number 2
June 2011
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
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.
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
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-
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-
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-
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-
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
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
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
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
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.
Table 1. Tentative S-101 development schedule
Phase Start Date End Date
____________ _____________
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
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.
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
Ward et al. 2009. IHO S-100: The New IHO Hydrographic
Geospatial Standard for Marine Data and Information. In-
ternational Hydrographic Organization. Monaco
00 IHO Universal Hydrographic Data Model (Ed 1.0.0
January 2010). International Hydrographic Organization.
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-
ISO 19100 Series Geographic information/Geomatics. Inter-
national Organization for Standardization. Geneva, Switzer-