Hydrographic survey

The examples and perspective in this article deal primarily with the United States and do not represent a worldwide view of the subject. Please improve this article and discuss the issue on the talk page.

NOAA Survey Ship

Private Survey Ship Neptune

DTM - Digital Terrain Model

Hydrographic survey is the science of measurement and description of features which affect maritime navigation, marine construction, dredging, offshore oil exploration/drilling and related disciplines. Strong emphasis is placed on soundings, shorelines, tides, currents, sea floor and submerged obstructions that relate to the previously mentioned activities. The term Hydrography is sometimes used synonomously to describe Maritime Cartography, which in the final stages of the hydrographic process uses the raw data collected through hydrographic survey into information usable by the end user.

Hydrography is collected under rules which vary depending on the acceptance authority. Traditionally conducted by vessels and with Echo sounding, surveys are increasingly conducted with the aid of aircraft and sophisticated electronic sensor systems in shallow waters.

When surveys are used for the purposes of chart making/distribution or dredging of state controlled waters they are commonly conducted by or under the supervision of national organizations. Hydrographic offices evolved from naval heritage and are usually found within national naval structures, for example Spain's Instituto Hidrográfico de la Marina^[1]. Coordination of those organizations and product standardization is voluntarily joined with the goal of improving hydrography and safe navigation is conducted by the International Hydrographic Organization (IHO). The IHO publishes Standards and Specifications^[2] followed by member states as well as Memoranda of Understanding and Co-operative Agreements^[3] with hydrographic survey interests.

The United Kingdom has a long hydrographic history officially begun with the 1683 appointment of Captain Grenville Collins as Hydrographer to the King^[4]. With the Royal Navy dominating the seas hydrography grew to a worldwide hydrographic activity. That tradition extended to the nations with a common legacy in the Empire, for example, the Australian Hydrographic Service^[5]. The British Admiralty Hydrographic Office became the United Kingdom Hydrographic Office which continues the legacy within the Ministry of Defence^[6] with responsibility for the Admiralty Charts^[7]. The Royal Navy maintains a number of hydrographic survey vessels^[8] to continue the work today.

In United States territorial waters hydrographic responsibility lies with the National Ocean Service^[9][10], a uniformed corps^[11] within the National Oceanographic and Atmospheric Administration (NOAA). The National Geospatial Intelligence Agency^[12] oversees charting of international waters and for Department of Defense purposes with the Navy's Naval Oceanographic Office^[13] conducting the surveys. United States Navy SEALS and Seabee Underwater Construction Technicians also have the ability to conduct hydrographic surveys. The SEAL/UCT operators are normally called upon before amphibious landings in order to survey the landing beaches. The Army Corps of Engineers conducts specialized surveys for dredging and marine construction and occasionally the Environmental Protection Agency conducts surveys, for example, on projects such as the GE/Hudson River Super Fund site.

Companies, Universities and investment groups will often fund Hydrographic surveys of public waterways prior to developing areas adjacent those waterways. One example of this would be surveys completed for Riverboat Casinos that ply inland rivers. These large ships require relatively shallow water, but it has to meet minimum depth requirements. Private surveys are also conducted before dredging operations and after these operations are completed. Steel mills and companies that have large private slips and docks have their facilities and open water near their facilities surveyed regularly.

Modern surveying relies as much on software as hardware. Equipment can be installed on inflatable craft, such as Zodiacs, small craft, AUVs (Autonomous Underwater Vehicles), UUVs (Unmanned Underwater Vehicles) or large ships, and can include sidescan, single beam and multibeam equipment.

After data is collected, it has to undergo post-processing. A massive amount of data is collected during the typical Hydrographic survey, often several soundings per square foot. Depending on the final use (navigation charts, Digital Terrain Model, volume calculation for dredging, topography, Bathymetry) this data must be thinned out. It must also be error corrected (bad soundings,) and corrected for the effects of tides, waves/heave, water level and water temperature differences (thermoclines.) Usually the surveyor has additional data collection equipment on site to record the data required for correcting the soundings. Final output of charts can be created in a combination of specialty charting software or a CAD package, usually Autocad.

References

External links

• International Hydrographic Organization
• IHO - Download / OHI - Téléchargement
• NGA - Products and Services Available to the Public
• United Kingdom Hydrographic Office
• Australian Hydrographic Service (AHS)
• Armada Esapñola - Instituto Hidrográfico de la Marina

NOAA maintains a massive database of survey results, charts, and data on the NOAA site.

• NOAA's Hydrographic Website
• Hydrography Blogspot
• Hydrographic Echo Sounder Company
• Survey software company
• Surveying software
• Hydro International, magazine for hydrographic surveyors
• Social & Economic Benefits of Hydrographic Surveys from "NOAA Socioeconomics" website initiative