The Relationship of Geomatics Standards to ICE in ECDIS

Ice in ECDIS WorkshopJune 1st, 2000

St John’s NFLD,

C. D. O’Brien,IDON Technologies

Background

For the past twenty years, many organizations have applied computer and information technology to assist in cartography, hydrography, geology, urban planning and other geographically related application areas.

At first individual organizations developed their own computer based systems to assist them in their existing procedures. This was primarily the collection of data and the creation of paper oriented products. This was the era of computer assisted cartography.

Commonality of TasksOver time the commonality between the tasks being

performed in different organizations was recognized. Manufacturers developed systems that were flexible to satisfy

each organizations particular need. From a manufacturer's point of view this was compatibility since the same equipment could be used for many purposes or by many businesses.

Of course, the equipment of different manufacturers was incompatible, but there existed a level of compatibility if an agency used a single equipment supplier. For many areas of use this represents the current situation.

Captive markets

Certain Geographic Information System (GIS) equipment manufacturers have dominated different market areas. This has led to a locking-in of clients to particular systems.

Vertical markets resulted. Data would have to be re-worked to be used in different applications.

From a data producer's point of view there was no standardization at all because data could not be published in a universally understood form.

Islands of Incompatibility

There is no shortage of standards. Many agencies and companies have developed their own proprietary standards.

Some are in wide use, whereas others have very narrow applicability.

Standards limited to particular application domains are actually barriers rather than aids in fostering interchange. They create "islands of incompatibility".

Application Area Standards

Standards did develop within organizations. If the organization was influential, it tried to

convince others within its community of use, to follow the standard.

This led to a number of different application area-specific standards and an isolationism, which discourages the reuse of data.

What Standards are Needed?

Each application area had its own view of what standards were needed. Much like the blind men viewing an elephant who all saw the elephant differently.

Standards as BarriersMany countries and organizations do not adopt global

standards. There are only two standard voltages (100-120) and (220 to 240) so there is only a need for two electrical plugs.

However many countries have different plug designs. This was originally intended to protect markets, but it ended up limiting trade.

Some groups don’t want compatible standards!

A number of different standardization developments are underway both internationally and within various nations addressing the exchange of geographic information.

In fact, one may say that there are too many standards efforts and not enough standardization.

A wide choice of standards results in limited use of each. The greater the range of possibilities, the more unlikely that two systems share a common exchange "language".

Too Many Standards

Facsimile was invented by a Scotsman over 100 years ago, yet the technology had few users up to the mid-1970s.

Interoperability was limited to equipment produced by the same manufacturer.

When the ITU-T / CCITT standardized facsimile so that all machines could interact, the market experienced tremendous growth.

What happened to Fax

Explosion of growth

The field of Geographic Information Systems is poised for an explosion of growth.

Almost everything is in some way geospatial. Conventional databases are including spatial

referencing, and everythingfrom accounting systemsto word processors are including "Map" type data.

DX 87, DX90, S57

In the late 1980's the International Hydrographic Organization began the development of an exchange standard for nautical chart data.

The initial standard, DX 87, provided a method of exchanging basic cartographic line work, with some objects.

Gradually this standard has been improved as DX 90 and then S-57 to address all of the information needed for an electronic chart.

S-57 and S-52

S-57 is an International Hydrographic Organization standard for Hydrographic chart data.It consists of an Exchange Standard, an Object Catalogue, and a

Product Specification for Electronic Navigational Charts (ENCs).

S-52 is a complementary standard that defines the performance of an ECDIS system.It includes a presentation library speciication.

Collectively these standards define the basis for Electronic Charting, and have been approved by the IMO.

DNC

The NATO DGIWG has also defined an exchange standard called DIGEST for geographic information in a broader military context.

There are many DIGEST products.One product is the Digital Nautical Chart.

Unfortunately the S-57 ENC and the DIGEST based DNC are not directly compatible.

Harmonization

Both DGIWG and IHO have worked together for many years to try to align ENC and DNC. A mapping from the S-57 Object Catalogue to the DIGEST

Catalogue is now complete, and the data models and meta objects are aligned.

DIGEST is adding ARCs and Update in line with S-57.

This allows for “dual fuel” implementations in ECDIS systems, and for dual production from the same source.

However, the two standards exhibit different characteristics that limit interoperability.

Abstract Model Standards

Another standards organization of importance is the International Organization for Standardization Technical Committee on Geographic Information Geomatics TC211.

ISO TC211 is developing a suite of abstract standards for all of GIS that will provide a framework for standards such as S-57 and DIGEST.

Using the TC211 base standards will allow application area standards to concentrate on the information content.

Content Models

The information content in a geographic information data set is the part of value.

The content model represents the data that can be converted into many different formats.

As long as these formats are capable of carrying all of the content, then the essential information is carried.

The content model and components

Defining information in terms of a content models and components is preferable to defining complete exchange standards.

Every set of data, whether it is temporary, or persistent and standardized, has a content model.

This content model can be expressed in terms of a modeling language, and basic components can be shared.

This increases the commonality between systems, since systems can be developed to support many different content models.

ISO Developing Components

The (ISO) is developing a suite of abstract standards and components form which to develop other common Geographic Information standards.

Standards such as S-57 and DIGEST will become TC211 profiles.DGIWG has announced that DIGEST edition 3.0 will

be at TC211 profile.IHO has not gone as far yet, but has indicated that the

direction is toward being a TC211 profile.

ISO TC211

Rules19109 Rules for application schema19110 Feature cataloguing methodology19114 Quality evaluation procedures19116 Positioning services19117 Portrayal19118 Encoding19119 Services

Components19107 Spatial schema19108 Temporal schema19111 Spatial referencing by coordinates19112 Spatial referencing by geographic identifiers19113 Quality principles19115 Metadata19123 Schema for coverage geometry & functions19125 Simple Feature Access - SQL

Reports (and input to other Projects)

19120 Functional standards19121 Imagery and gridded data19122 Qualifications and certification of personnel19124 Imagery and gridded data components

Guidance19101 Reference model19102 Overview19103 Conceptual schema language19104 Terminology19105 Conformance and testing19106 Profiles

An S-57 Content ModelS-57 is a feature oriented boundary (vector) based data

description. It currently defines:an Object Catalogue including capture rules;a data model consisting of an application schema and spatial schema;a set of attributes data in the application schema which forms a list of

information about the information (i.e., metadata).

This is the S-57 content model. It is important in that it does not change. However, it can be described differently.

Describing it in terms of the TC211 suite of standards will make it easier to use other commercial software to implement the content model.

An ISO compliant encapsulation

ISO TC211 separates encapsulation from data content. It defines a general encapsulation standard ISO 19118

that describes the method of converting a content model or schema element into a general exchange structure and then converting that exchange structure into one of several possible encoding formats.

An neutral XML encoding format is defined as the default encoding.

8211 obsolete

ISO 8211 is now obsolete. ISO JTC1 has considered dropping the standard, and the

maintenance of the standard is not currently assigned to a sub-committee. The standard is retained as a "mature" standard as long as it is being used.

IHO TSMAD is considering developing an XML encoding, as an alternative for S-57 edition 4.0.

(retaining the older approach for backward compatibility)

Portrayal

An important aspect of the IHO work on electronic charting is the S52 Presentation Library. In IHO this is considered to be separate from S-57, but it is driven by S-57 objects.

A similar portrayal standard has been developed in TC211. It defines a generic object centered rule based presentation mechanism that is compatible with the IHO S-52 presentation library. In fact the work on the TC211 CD 19117 on Portrayal has been heavily influenced by the IHO work.

The TC211 standard defines a general rule based presentation mechanism that fits in the TC211 model. In this context the IHO presentation library is a set of rules that would drive the ISO mechanism.

Update

ISO TC211 has addressed the issue of update as part of its work on CD 19118 Encoding.

It has taken the IHO (Add, Modify, Delete) incremental update approach.

DGIWG is also now considering this approach.

ICE Data

There currently is no standard for ICE chart data. The data is supplied in the format the customer wants.This is expedient in the short term, but inhibits the development of commercial systems and services.

ICE chart data is of two types:Vector chart overlays, and Raster satellite imagery.

Vector OverlayThe vector based overlay of a hydrographic chart with

ICE data can be accomplished with the addition of a few new objects and attributes to an S-57 data set.

These objects and attributes were developed about 5 years ago through a series of ICE data workshops, but they were never added to S-57 (for several reasons).

These will be discussed separately

An S-57 add-onThe basic S-57 exchange standard can handle

additional these additional objects, and it is likely that most ECDIS equipment could handle it with little or now change.

Some new S-52 presentation rules will be needed. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - One barrier is that nobody wants to touch the S-57

document because it contains the IMO approved ENC product specification.

MIOs

IHO is also studying Maritime Information Objects as an add-on to S-57.

Vector based ICE objects can be added as a new IHO specification (S-63) through thye MIO committee without touching the existing S-57 document.

A draft standard for trials could be developed very quickly. (I feel that this should be a recommendation of this

workshop.)

Raster/Image DataThere are a very large number of imagery

standards for different uses (HDF, CEOS, ISPRS, DIGEST, BIIF, Geo-TIFF).

ISO TC211 is developing a common content model and structure for coverage type data (allowing for different encodings)

IHO TSMAD has indicated that it will not develop its own Raster/Image standard, but use the TC211 work.

Linked Raster

Both vector and raster data can be geo-referenced and co-presented.

Raster data can also be object linked.TC211 is also supporting complex

“coverages” such as sonar sounding data and satellite radar data.

ICE in ECDIS Standards

Vector based data that complements a S-57 ENC.A new IHO (S-63?) as an add-on to existing ENC.Draft based on previous work.Proceed to testing

Linked Raster/Image data.Based on TC211 “coverages” work (as per IHO)Initially only geo-referenced images.

Both to work together.

For additional information contact:

C.D. O’Brien,IDON Technologies Inc.

280 Metcalfe St. Suite 301Ottawa, K2P 1R7

dobrien@idon.com

Additional Information