NIMA digital chart to set sail with Navy

The National Imagery and Mapping Agency is preparing a database that could replace the paper charts sailors use to navigate, although some seamen have concerns about the accuracy of NIMA's new digital chart.

NIMA officials hope to make the Digital Nautical Chart (DNC) available to about 600 Navy vessels in its first-edition form by March 1999. The chart will come in the form of 29 CD-ROMs for various regions of the Earth and will function as an interactive electronic map that sailors can use to get quick information on nautical features such as cultural landmarks, land cover and ports as well as obstructions such as underwater cables.

Clicking on an item on the electronic chart will bring up detailed information that a sailor does not necessarily have at his fingertips when he uses traditional paper maps or the electronically scanned and static, or raster, images of maps.

"Instead of having 200 to 500 charts rolled up on your deck, you have it all right here," said Steve Higgins, a member of the CD production team at NIMA and coordinator of NIMA's DNC World Wide Web site

NIMA already plans to give the public— not just the Navy— a healthy dose of the potential of DNC because NIMA officials expect the product ultimately will be used by private-sector navigators. Last month NIMA demonstrated the digital chart aboard the USS Constitution. Higgins said NIMA in the next couple of months will begin to flesh out a public Web site for DNC, complete with a DNC white paper and sample data.

One promise of the DNC, according to Higgins, is that users will be able to see only what they are interested in and only the layers of data they choose.

"The fact that you have it in a database— it gives you a tremendous amount of power," said Winfield Vining, department head for geographic information systems mapping at Greenhorne & O'Mara Inc., a company that is helping create the DNC database from static charts. "You basically can clean up your chart, and it isn't as cluttered as a hard copy would be," Higgins said.

Nor would it be as cluttered as the static electronic raster images of charts that are the meat and bones of many navigation systems used aboard ships today.

But the paper charts, and therefore electronic copies of the paper charts, are frequently inaccurate, according to people who use them.

"It's terrible. They're inaccurate," said Steve Nadeau, a pilot who brings commercial ships into port at Miami. "They're all raster-scanned." And if NIMA builds its DNC on the inaccurate charts that sailors are using today, the same inaccuracies will result, he said.

What is needed are new surveys of ports because that is where navigation is trickiest— among heavy traffic, buoys, channel markers and berths, Nadeau said. "What we have found is the inaccuracy of the charts [is] not practical for the mariner," he said. "That's why you have pilots in ports" available to help guide ships in safely.

No one is claiming, however, that the charts— paper, electronic raster or DNC— are perfect. "I guess I would argue that that problem [of inaccuracy] exists regardless of the format of the data," said Jim Ciarrocca, who has served as a DNC project manager for NIMA contractor Environmental Systems Research Institute Inc.

But the federal government continues to strive for accuracy in charts. Ciarrocca said NIMA and other agencies whose missions touch on navigation constantly are updating a database known as Notices to Mariners. The notices are updates or corrections to existing charts and are disseminated as supplements to charts, not as brand-new charts.

That means sailors who are using charts today must consult with a chart as well as a separate source of Notices to Mariners to determine their course. The task can be cumbersome, but with the new DNC, all the information will reside in one source, NIMA officials said.

Jim Moran, chief of a NIMA branch working on DNC, said the agency is working with the Navy to develop software that will let users download the notices and layer them over DNC images.

In fact, NIMA outsiders likely will develop a lot of the software that will be used to read the raw DNC data that NIMA is putting on CDs. Already, the Space and Naval Warfare Systems Command Systems Center in Norfolk, Va., and Litton/

PRC Inc. have helped develop software that displays a chart using the DNC data. And NIMA last year announced it was working under a cooperative research and development agreement with Litton Marine Systems Inc. to develop software to read and display DNC data.

Other applications expected to emerge would tie Global Positioning Systems into the DNC so that sailors would be able to see their course in real time. "That gets people excited, that they can actually see their position on the chart as their vessel [moves]," Higgins said.

But Nadeau has his doubts about how well that will work because many charts are riddled with inaccuracies. "You can't do it in an automobile. How can you do it on a ship?" he asked. "The No. 1 way to navigate: You look out the window."