Approximately 25 USACE districts located throughout the country provide NOAA with charting information. NOAA relies exclusively on the Corps of Engineers to provide survey and tabular information concerning the 926 Federal harbor channel projects that support the U.S. port system. The U.S. deep-water port system includes more than 300 Federal harbor channel projects. There are 51 ports with depths greater than or equal to 40 feet. Clearly, federal channels are the main arteries of our nation’s waterways. It is imperative that the mariner has accurate depth and position information about these thoroughfares.

Federal Channels

The USACE and its contractors routinely conduct hydrographic surveys of federal channels. These surveys may be performed in order to ascertain the condition of the channel. They may also be conducted in conjunction with dredging (pre or post dredge surveys). The Corps is obliged by law (33 CFR Sec 209.325) to forward the results of these surveys to NOAA in order that the depth information can be conveyed on nautical charts.

Depth information for federally maintained waterways are depicted on nautical charts in several ways. In general:

1) Channels that are 400 feet wide and greater: A tabulation on the chart will show minimum depths in each quarter of the channel.
2) Channels 100 to 400 feet: A tabulation will show minimum depths for the left outside quarter, mid-channel for half project width and right outside quarter
3) Channels less than 100 feet width: Report controlling depths only based on at least 80 percent of project width: 40 percent on either side of the centerline.

In the tabulation shown above, the Brewerton Channel is 3.06 miles long and 700 feet wide. The authorized project depth is 50 feet. A survey conducted in September and October 1996 show the actual or controlling depths to be less than the project depth. The controlling or minimum depths in the outside and inside quarters are displayed in the tabulation. These represent minimum depths at the time of the survey

USACE hydrographic surveys are typically conducted at a large scale (e.g. 1:2,500) with high-resolution detail. Since typical NOAA charts are printed at smaller scales (e.g. 1:10,000), all of the detail contained in the USACE survey cannot be shown. The figure below shows a highly detailed Corps survey and its corresponding depiction on a paper chart.

Corps districts throughout the country forward their survey blueprints to NOAA. These blueprints were traditionally provided in paper format. However increasingly, the Corps provides NOAA with digital versions of surveys. Some districts compute their own channel tabulations and provide this information to NOAA in addition to the surveys. Other districts provide NOAA with the surveys and NOAA cartographers create the channel tabulations.

In most cases, new USACE channel surveys will precipitate changes to currently charted channel tabulations and legends. This information may be critical to mariners; therefore, NOAA generates chart updates that are forwarded to the Coast Guard and National Geospatial Intelligence Agency for inclusion in Local Notice to Mariners and Notice to Mariners.

NOAA and the Corps are working closely to develop a channel framework database. With the advent of high accuracy positioning and electronic charts, it is imperative that the precise geographic coordinates of channel boundaries be available to the mariner. The channel framework database consists of the outside channel limits, quartered sections of the channel as well as reach locations within the channels.

Construction Permits

Before new construction can take place in or along a waterway, individuals must apply for a permit from the USACE. Corps districts throughout the country forward these permits to NOAA. Usually, there are engineering plans that accompany the permit. However, NOAA does not automatically receive “as-built” drawings, once the project is complete. Very often, NOAA cartographers will have to track down “as built” drawings after the construction is completed. From these drawings, additions, deletions, and changes to the chart can be made.

Data Exchange

NOAA and the Corps are working together to develop more seamless and consistent data exchange formats. Corps districts do not use a universal software system for processing channel surveys. Most districts currently process and plot surveys using computer aided draft and design (CADD) software such as MicroStation or AutoCAD. NOAA’s paper and raster chart production system is based on MicroStation software. However, both NOAA and the Corps recognize that efficiencies can be gained by moving their processing environments to Geographic Information Systems (GIS). NOAA and the USACE are in the process of building new charting databases that will lead to standardized data exchange. The Electronic Navigational Chart (ENC) is a vector database of chart features being built to the International Hydrographic Organization's S-57 standard. NOAA, as the U.S. hydrographic office, is exclusively responsible for production and authorization of ENC data in U.S. coastal waters and Great Lakes. The Corps has also adopted the S-57 format to build its suite of Inland Electronic Navigational Charts (IENC). These electronic charts will serve users of inland waterways who have traditionally relied on Corps paper charts. The Corps is moving toward providing NOAA with electronic survey data in S-57 format.