How accurate are the data and what is the density of soundings in ——- area?
The NOS hydrographic survey database is a historical set of surveys. In fact, some of the digital data sets are digitized from surveys that were conducted in the late 1800’s! Accuracy is difficult to determine for these surveys. Recently (after 1965) rigid standards were maintained for survey control. These accuracy standards and requirements are stated in the NOS Hydrographic Surveys Specifications and Deliverables publication, which focuses on the minimal criteria needed for both in-house and contract NOS surveys. The Hydrographic Manual Fourth Edition is an older (4th edition published in 1976) and more comprehensive document that covers all stages of the hydrographic survey process at NOS, and can be purchased from the Hydrographic Surveys Branch, Data Control Section (301) 713-2710. Data density requirements are covered in the Hydrographic Manual.
