For the time being, these vector charts, dubbed electronic navigational charts (ENCs), will only provide coverage for those areas of prime importance to shipping. However, the coverage of ENC chart products could expand to cover more areas of interest to recreational mariners. Raster charts, like the NOAA/ Maptech charts, look exactly like NOAA paper charts. They should since they are digital pictures of the actual NOAA charts. The great advantage of the raster approach is that it presents the mariner with the actual chart that he or she is familiar and comfortable with. While a raster chart is a "picture" of a paper chart, a vector chart is a database, a set of data packages, rather than a fixed graphic file. Early vector-based charts didn't look much like paper chartsthey were often monochromatic, and when they did use color they were often less graphically rich than paper charts. This changed a few years ago with the introduction of new vector-based products from the two major vector chart providers, C-Map and Navionics. These vector-based charts have a color scheme and symbology that are closer to paper charts. Now, NOAA is ready to offer a vector product to complement its raster charts. "These are not intended to replace raster charts," said Dave Enabnit, technical director at NOAA's Office of Coast Survey. "We will be making these charts available for a test period of six months." After that time, the charts will be withdrawn and then reissued in the fall. The six-month availability will allow mariners to use the charts and comment on them. According to Enabnit, NOAA sees these charts as a work in progress. Features will be added and deleted based on feedback from users and software developers. These ENC vector charts from NOAA are intended primarily for professional mariners. They will have coverage of 100 U.S. ports and will be restricted to main shipping channels. Because the vector-based ENCs will be constructed from the original survey data, some of it new, and not digitized from existing paper charts, NOAA is claiming that ENCs will be more accurate than the NOAA/Maptech raster charts. Standard-setting organizations like the International Hydrographic Organization (IHO) have long held the belief that the only truly useful future chart will be vector based (NOAA's ENC products are formatted in IHO's S-57 vector chart format) not raster based. Thus, these ENC charts could well be a glimpse of the future. Raster charts will continue to be offered for recreational mariners and for low-accuracy applications. But for large commercial vessels and for those yachtsmen who will be willing to pay extra, ENC charts will provide added accuracy. See NOAA's web site (chartmaker.ncd.noaa.gov, click on the "what's new" link) for the latest.
