Charting a Course into the Digital Era: Guidance for NOAA's Nautical Charting Mission (1994)

Changes in information technology often require organizations to adapt to new modes of operation. This is true for geographic data—data referenced to the surface of the earth. The value of geographic data has been accentuated through its widespread use in geographic information systems for many purposes, such as infrastructure planning, demographic analysis, and environmental research. A geographic information system is a system of spatially referenced information, including computer programs that acquire, store, manipulate, analyze, and display spatial data.

Traditionally, government organizations have used paper maps to convey spatial information. Increasingly, they are required to integrate disparate data types for coherent analyses of complex problems. To fulfill this responsibility, many public agencies, such as the U.S. Geological Survey and the Bureau of Census, have invested in state-of-the-art computerized technologies, especially automated data collection techniques for generating source data and geographic information systems for spatial data analysis. The Federal Geographic Data Committee, of which the National Oceanic and Atmospheric Administration (NOAA) is a member, is developing standards for facilitating exchange of spatial data among federal agencies.

The availability of these new technologies has had a profound impact on producers as well as users of traditional map products and will inevitably affect the way future data bases will be constructed and disseminated. The emergence of associated technology has been a major catalyst to the growth of the spatial data industry, which now conducts several billion dollars worth of business annually.

The availability of new and evolving information technology provides new options for how nautical data are managed, disseminated, and used. Digital technology gives data producers and users powerful tools to store, transmit, update, view, and manipulate information about the marine environment. The nautical charting world reflects these changes in a growing demand for digital data sets to support electronic charts and other uses of marine geographic information and in new automated nautical chart production systems.

This chapter begins with a review of the rationale for making the maintenance of a national nautical information data base a central focus of NOAA's nautical charting activities. It provides an overview of NOAA's efforts to develop an automated nautical chart system and reviews the agency's plans to develop a data base of digital nautical

information. The chapter concludes with a discussion of issues associated with implementation of the nautical data base and suggestions for focusing NOAA's effort.

The U.S. government, through NOAA, assumes liability for the navigational data it certifies for use. To fulfill this responsibility, NOAA must establish and enforce standards by which survey data are collected, entered into the data base, and disseminated. Data acquisition (Chapter 3) and product distribution (Chapter 6) are aspects of its mission that NOAA can delegate, at least in part, to the private sector. Maintenance and control of the master nautical data base for the nation's ocean and coastal waters—the ultimate source of the information disseminated in nautical chart products—will be the central aspect of NOAA's future nautical charting mission. This activity is a "natural monopoly," intimately tied to quality assurance and, therefore, a function appropriately managed by a federal agency as a unique and specialized mission. In the future, maintenance of the master nautical data base and associated functions is likely to be the most important component of NOAA's in-house nautical chart and information activities.

In the past, NOAA's data base was a collection of survey records and analyses of surveys recorded on paper. Recently, it has also included digital records of surveys; in the near future the data base will consist primarily of digital data. Reaching this objective requires the conversion of much existing data to digital form in a centralized digital nautical data base. The Automated Nautical Charting System (ANCS II) currently is being developed by NOAA as a means of automating the production of paper chart products from such a data base.

ANCS II is a computer system designed to support the production of a consistent and up-to-date suite of NOAA nautical chart products from a digital nautical data base known as the nautical information data base (NIDB). The NIDB is the ANCS II-specific master nautical data base and is one possible implementation of the digital nautical data base described above. Using digital data to produce paper chart products can lead to a much more efficient means of implementing the entire production and maintenance process than the current updating methods. Unless the process is transformed by these new technologies, it is inconceivable that NOAA could ever slow the growth of the backlog of new chart requests described in Chapter 3.

Ultimately, development of a digital nautical data base for U.S. waters is the crucial element for improving all nautical information products. Official chart data in digital form are in demand not only from present and potential users of electronic charts but also from many nontraditional users of chart information (see Chapter 5). All of these demands can be met only if NOAA builds and maintains a robust digital nautical data base.

ANCS II, which is expected to be operational in fiscal year 1994, was designed primarily to facilitate the production of paper charts. The ANCS II NIDB (which may form a basis for a digital nautical data base) will contain a superset of all features (e.g., buoys, water depths, tidal variations) shown on all chart products. All updates from surveys and other sources are to be applied to this data base, and NOAA's product updates will be derived from the NIDB using operators' cartographic decisions stored in a separate chart graphics data base.

There are numerous advantages to the automated approach embodied by ANCS II. For example, since chart currency is known, and the NIDB is constantly updated, the system can report on how outdated each product edition is relative to the data base. The best information is used; updating is expedited, and resources are used more efficiently; and, as a product moves toward release, managers can monitor new changes in that area and perform last-minute updates as needed.

A major benefit resulting from full development of a digital nautical data base would be the basis for support of official digital data sets for electronic chart users. Future goals include making ANCS II the source of a suite of digital products, including digital nautical charts for the Defense Mapping Agency and data for International Hydrographic Organization member countries and users of electronic chart systems. Another future goal should be to extend ANCS II to accept and produce data in the appropriate format for use by nonnavigational users of marine information for various applications in a geographic information system (see Chapter 5). ANCS II has the potential to significantly improve the rate at which new chart information is disseminated to users, and to help meet the demand for digital products, if all extensions are implemented.

Detailed analyses of the NIDB and ANCS II design, implementation, acquisition, and extensions were beyond the scope of this study. It is not clear that present plans and processes surrounding ANCS II address the requirements described above in the most efficient way. For example, it is not certain whether a system designed for paper chart suite production can readily be extended to support the content and compilation requirements of digital products. The committee's endorsement of the ANCS II NIDB loading effort is based only on the recognition that the NIDB conceptually resembles the master digital nautical data base, which is essential to improving the efficiency of NOAA's nautical information activities in the future.

Converting paper chart data to the digital format required for the ANCS II data base involves two steps: digitization and attribution. Digitization is the process of constructing a numerical description of the lines, points, and other features shown in the paper chart. It is commonly accomplished by first scanning the paper chart to produce a "raster image" or digital picture of the chart and then building a vector data set from the image. Vector data describe individual features by geographic coordinates. Geographic data stored in vector

format can be manipulated and interrogated by logic built into the software; it enables "intelligent" queries and analyses of the features embodied by the data. Pure raster data, by contrast, are simply a digital picture and do not readily lend themselves to intelligent manipulation; such data have the advantage of being easier to display. While vector/raster hybrid data may be used to capture the advantages of both data types, some vector data are necessary for the operation of marine geographic information systems and electronic chart technologies. The committee's vision of a digital nautical data base does not preclude raster data but has at its foundation a vector data set.

Attribution is the addition to the vectorized data of feature codes and text describing each of the objects (shoreline, depth contours, buoys, soundings) that make up the chart image. The two operations—digitization and attribution—are labor intensive and therefore time consuming. Digitization and attribution are estimated to account for 80 percent of the total data collection and loading effort in terms of both time and costs (McCarty, 1991).

Loading the ANCS II data base with all information presently contained in NOAA's suite of paper charts is expected to require 8 to 10 calendar years given present levels of effort and resources, at a cost of $20 million (about $20,000 per chart in the present suite). Under present plans, the Defense Mapping Agency will bear about 25 percent of the cost of data capture, which will support part of the digitization and attribution of 475 charts covering Navy home ports over a period of approximately 5 years. NOAA's attempts to raise funds to capture the remaining data have been unsuccessful to date.

Faced with an extensive and largely unfunded effort to load the ANCS II data base with vector data, NOAA has recently pursued a second approach to automating its paper chart production system for the 75 percent of the chart suites for which vector data collection is unfunded. This approach entails preparation of a separate data base of raster chart images, which are much less expensive to generate since they do not require vectorization or attribution. These raster images can be edited and used to produce printing plates, thereby reducing the delays now associated with printing new editions.

While the raster images contain the same source information from which vectorized data ultimately will be produced, the plan to maintain and support a separate raster data base represents a significant departure from the goal of rapidly populating the ANCS II vector NIDB. This activity threatens to divert resources from the development of the NIDB and to delay further the time when the full advantages of a vector-based master digital nautical data base will be attained.

The production of color separations and printing plates from a raster data base is a relatively simple task, but maintaining the raster data requires manual editing of raster images, which is skill intensive and time consuming, even when software tools such as CAR (computer-assisted revisions) and SCAR (super CAR) are used. When the update is relatively simple, the raster editing required is straightforward. For major changes, such as a new hydrographic survey, the raster editing required is likely to be quite time consuming.

NOAA plans to accumulate changes between chart editions (e.g., changes to navigational aids and features) in the ANCS II NIDB, making the NIDB principally a data base of changes rather than all chart source data. Raster images of the changes are to be produced through the normal production path in ANCS II and integrated by raster editing with the raster image of the chart. Operating ANCS II as a changes-only system in parallel

with a full raster data-base effort promises to be an inefficient and expensive use of ANCS II.

While the raster data-base approach may lead to faster turnaround times for new editions of some paper charts in the short term, there are questions about its overall efficiency. Moreover, this approach does not advance NOAA toward the goal of a single unified vector-based master digital nautical data base. The additional effort required to maintain the raster data base may increase the time required to attain this goal.

It is questionable whether it is necessary to capture all possible chart data attributes during the initial ANCS II loading process. For example, all attributes not absolutely required for the paper chart production process, such as archival source data information, could be added at a future date without much loss in functionality. An efficient approach would be to retract the plan to maintain a raster data base and use all available resources to push the population of a digital nautical data base (such as the ANCS II NIDB) to fruition as quickly as possible, eliminating as many of the attributes as is consistent with safe and accurate paper chart production. This, of course, means providing sufficient attribution concerning change information to maintain NOAA's high standards of quality assurance and control. This approach would move NOAA closer to the ultimate goal of a fully attributed digital nautical data base, while it brings a fully automated chart production and updating system on-line as quickly as possible. Full attribution of the data can be performed later.

Additional avenues exist to leverage resources outside NOAA to help in populating the digital nautical data base. The power of geographic data standards to enable the integration of diverse data sets is tremendous. (See Kottman, 1992, for an introduction to digital geographic information exchange standards.) The adoption of universal geographic data formats and exchange standards can open avenues to accelerated loading of the digital nautical data base.

For example, some of the data are routinely collected by or for the U.S. Army Corps of Engineers in the form of project surveys. Incorporating such survey data into the NOAA master data base in digital form can help load the data base and lead to shorter production times for new large-scale charts. This merely requires agreement on data standards between NOAA and the Corps of Engineers.

State coastal management and port agencies have also been collecting data for their local areas, and NOAA might consider forming alliances with these agencies to incorporate available data, where accuracies are sufficient, into the master digital nautical data base. State and local governments are likely to be receptive to partnership agreements with NOAA (see Chapter 5), under which the partner might digitize NOAA charts coveting its geographic domain in return for digital updates in the future. Such agreements would require established guidelines for digitization and procedures for disseminating digital updates.

NOAA is to be commended for initiating the development of an automated digital nautical chart production and management system. However, the agency now appears to be focused on a raster data-base maintenance project in an effort to speed up paper chart production. Maintenance of a separate raster image data base threatens to divert limited resources from the population of a vector-based master digital nautical data base and is not an efficient way to effect the improvements in chart production time that NOAA envisions. A more fruitful course for NOAA to follow into the digital information future lies in focusing on a lean approach to attribution and a full effort at vector digitization.

Kottman, C.A. 1992. Some Questions and Answers About Digital Geographic Information Exchange Standards. Second edition. Intergraph Corporation, Reston, Virginia.

McCarty, T. O. 1991. Data Collection Experiences for an Automated Nautical Charting System. Unpublished Intergraph White Paper. Reston, Virginia.