Hi Reddit! We’re Rear Admiral Shep Smith, Director of NOAA Coast Survey and the U.S. National Hydrographer, and Lt. Cmdr. Sam Greenaway, chief of NOAA Coast Survey’s Hydrographic Systems and Technology Branch, and we are experts in mapping the seafloor. Ask us anything!


Today is World Hydrography Day! Hydrography is the science that measures and describes the physical features of bodies of water and the land areas adjacent to those bodies of water. Here at NOAA, we are experts in hydrography and are responsible for mapping 3.4 million square nautical miles of the U.S. seafloor and 95,000 miles of coastline.

NOAA’s Office of Coast Survey conducts hydrographic surveys to measure the water depths to ensure the coastal regions of the United States are safe for boats and ships to navigate. We use the data to update nautical charts and develop hydrographic models; increasingly, we use hydrographic data for multiple purposes including habitat mapping. NOAA hydrographic ships are equipped with sophisticated multibeam echo sounders that survey large swaths of the ocean floor, collecting a tremendous volume of bathymetry (or depth) data. We also look to emerging technologies and methods to map the seafloor including the use of satellites and crowdsourced data.

We’re here today from 1:00-3:00 ET. Ask us anything about how NOAA maps the U.S. seafloor!

Thank you to everyone who joined us today! It has been great chatting with you all about mapping the U.S. seafloor. We hoped you learned a bit about why we map the ocean seafloor, how we collect bathymetric data, and the navigational products we produce using hydrographic information.

NOAA Coast Survey is celebrating World Hydrography Day all week. Our daily hydrography- and bathymetry-related stories from earlier this week can be found on the World Hydrography Day page of our website.

With 3.4 million square nautical miles of ocean to map in the U.S. exclusive economic zone, our work is ongoing. Stay up-to-date by following our Coast Survey blog and social media pages:

Are you able to find shipwrecks with the equipment you use? If so can/do you pass info on locations to marine archaeologists? Last but not least, what is the strangest thing you found while mapping the sea floor?


Sam: Yes, for most coastal surveys, we are trying to find all hazards to navigation -- so we find wrecks quite often. We do have policies and procedures in place to determine if the objects we find on the seafloor are protected historic sites before releasing information about them to the public. We have a Wrecks and Obstructions database where you can view some of these wrecks. (Note: these resources may be protected by federal laws that prevent disturbance of historic and culturally significant artifacts, so the interactive map is a great way to take a look while staying dry.)

Strangest thing on the seafloor? The geology is pretty endlessly fascinating. We did find a bunch of old wooden Chris-Craft power boats all sunk in a line in a harbor in WA. Probably the strangest -- or at least the most interesting -- things I have seen are the stuff in the water-column, ocean boundary layers, the diurnal migration of plankton.

How do you view the challenges with storing, cataloguing and making discoverable these massive data sets? Where do you see the technology going in this area in the future, and is it keeping pace with the increasing size of swath bathymetry data sets, and especially water column data sets?


Sam: The data volumes are certainly a challenge. Just for context, one mapping system running in 20m of water might log data at a rate of well over a Gbyte per hour - over 35 Gbyte if we start logging full water column. And that is just the raw data. Data storage is a challenge -- USB hard drives are cheap, but robust, fail-over protected, and fast storage is expensive. Building networks to get fast access to all that data is not simple - and that's just on our side. Counter-intuitively, the shallow water multibeam systems acquire much higher data volumes than the deep water systems.

NCEI has been doing some nice work making all this data more discoverable. For our survey work, I think the portal at NCEI is a nice interface. I know NCEI has also been working towards making the watercolumn data more discoverable. They have been processing the data so a thumnail image is available before you download the data.

It is hard to keep this much data 'spinning,' so much of the raw data is in archive but needs to be retrieved on request. The cloud might help here.

In what have you seen the ocean or gulf floors altering as we intensify shipping with bigger and heavier ships while also causing more sedimentation to flow from rivers. Cheers and thank you for the AMA


Shep: TBH we don't see that much seafloor alteration from bigger ships themselves. That is kind of a good thing, since it might mean ships are hitting the bottom and we try to avoid that here at NOAA. What bigger ships can mean is more dredging so that they can get into port with the food, fuel, and goods we buy every day, and get out of port with our global exports. Dredging happens in channels that are designated for this kind of traffic (U.S. Army Corps of Engineers), but outside of the channels, most ships are hopefully not running aground. We did see one nice ship-shaped depression adjacent to a channel. We often see wash marks from ships and tugs during docking. Offshore, we see trawl marks from fishing. Sedimentation can happen for a lot of reasons -- run-off, erosion, development, etc. -- and the soil may cause a channel to fill up and need dredging.

Why is the military involved in a civilian agency? Do civilians do this work too?


Shep: I am guessing that you are referring to my rank and that of LCDR Greenaway. We are both NOAA Corps officers. The NOAA Commissioned Officer Corps (NOAA Corps) is one of the nation’s seven uniformed services. NOAA Corps officers are an integral part of NOAA, which is in the Department of Commerce. The NOAA Corps today provides a cadre of professionals trained in engineering, earth sciences, oceanography, meteorology, fisheries science, and other related disciplines. Corps officers operate NOAA’s ships, fly aircraft, manage research projects, conduct diving operations, and serve in staff positions throughout NOAA right alongside civilian scientists and personnel. You might look into the NOAA Corps as a job -- really a way of life. In what other job can you do so many cool things all at once? You can learn more here. We also have wage mariners and civilian physical scientists doing similar work, so yes, civilians do this work too.

Do you use synthetic aperture sonar at all? Why or why not?


Sam: We have not yet used synthetic aperture sonar (SAS) for production hydrography -- but we did just get a scientific data set for evaluation. To date, SAS systems provide spectacular resolution and wide swaths, but often at the expense of slow vehicle speeds, pretty strict requirements for navigation accuracy, and cost. That said, I know a number of vendors are working hard at bringing this tech. to different markets, and I expect we will see some interesting developments in the next few years. We are keeping a close eye on it.

Hello and thank you very much for such a cool AMA!

My questions are the following:

  • how long does one seafloor mapping campaign typically last and how wide is the seafloor surface covered? Do you need very good weather conditions for that (as in: can you still obtain data during a small storm for example)?

  • does the presence of marine mammals disturb seafloor mapping campaigns? If so, to what extent (does it extend the duration of the campaign in terms of hours or days or weeks?)

  • are there, today, any geological structures that are difficult to identify with the current tools that you use for seafloor mapping (underwater volcanoes, faults, other)?

Again thanks for answering that and all the best to you!


Shep: Thanks for the questions! Our ships and contractors usually work on a campaign for a few months a year. Sometimes there is a preferred time of year to work in an area, based on the weather, ice, traffic patterns, and presence of marine mammals. For larger projects, we will return to the same area several years in a row. We are very careful that our work does not disturb marine mammals. Our sonars are typically high frequency and operated at minimal power. We choose our project timing to avoid the seasons where Northern Right Whales congregate in certain areas, for example. We have a lookout posted and suspend survey operations for whales in the vicinity. Geologic structures...it is really a question of resolution. We typically resolve features from surface sonar systems to around 2-3% of water depth, so if the spatial resolution of the feature is finer than that, we may not be able to map it from the surface. With an AUV (Autonomous Underwater Vehicle), we can map to higher resolution in deeper water, since the AUV carries the sonar closer to the seafloor.

Hi and thanks for joining us today!

  1. What are the future ramifications of the Gulf of Mexico hypoxic zone?

  2. Don't know if you're allowed to talk about climate change but what is the most likely impact on our waterfronts/ways in the next 20 years due to raising/warming oceans?

  3. What's the deal with Lake Mead, is it likely going to run dry soon?


Sam: I think I can best tackle your second question and leave the other two for folks with more expertese at NOAA (climate) and at USGS (Lake Mead). You ask a good question about what will happen to waterfronts and waterways with sea level rise. It is certainly true that the sea level is rising in many places -- both due to global sea level rise and local land area sinking (a particular problem in places like Norfolk and Louisiana).

Ports and cities/states with developed waterfronts will have to decide what to do about their waterside and transportation infrastructure -- do they build higher, do they relocate, do they come up with other mitigations? Many of our coastal airports and highways were built in these low-lying areas also, because the land may have been considered marginal or easy to build on at the time. Twenty years isn't too far out, but we are already seeing more frequent flooding from storms, even just heavy rainstorms, e.g. Norfolk, VA. On the other hand, increasing water levels might mean more vessel traffic and commerce, which could be beneficial. So these places have a lot of decisions to make on what to do to reduce their vulnerability to rising waters. For more information: Is sea level rising?, What is high tide flooding?

Wouldn’t hurricanes move debris around under water? How do you handle that?


Sam: They not only move around what is there. Hurricanes can also put a tremendous amount of new debris into the water. The only way to make sure a port is clear after a storm is to survey it. We have mobile Navigation Response Teams to do this kind of work, but have also used the bigger hydrographic ships, ships of opportunity with portable survey gear, autonomous underwater vehicles, and contract surveyors for this work.

Can you use your raw data beyond just seafloor mapping for any water-column science? For example is there any backscatter from microorganisms or modification of the ray paths by temperature / salinity gradients?


Sam: You bet! Bathymetry is an important layer in many areas beyond navigational charting -- I am aware of its importance to fisheries habitat work, ocean dynamics modeling, storm surge modeling, coastal engineering (e.g., offshore wind), but there are probably other applications I have not even heard of. One thing we take seriously is making all our data available for anyone who wants to use it. All our raw and processed data (including the all important metadata) is archived at NOAA's National Centers for Environmental Information NCEI. You are welcome to use it however you like. For a specific example, here is one of the first surveys I worked on.

We do log seafloor acoustic backscatter for all surveys. This is useful for our charting work, but also hugely important for other applications. As for water column returns, we do not currently log full water column data from our shallow water multibeam systems all the time -- it's just too much data. Fisheries and other scientists do collect water column acoustic data from single beam or split beam systems -- and all that is archived here. I know NCEI is working hard to make this data more accessible -- check it out and give feedback if you like it (or have suggestions to make it better).

We also archive all our sound speed profiles (often including temperature and salinity) at NCEI - check out all the archives.

RADM Smith and LCDR Greenway, thanks for taking time to answer questions.

Could you comment on the often repeated: "less than 10% of the ocean has been explored/mapped?"

Also, is it true that many of the soundings used in nautical charts are "historical", that is pre-dating modern bathymetric methods?

Lastly, how does your mission benefit from scientific bathymetric mapping, and can it be used in your charts?


Sam: Thanks for asking this one -- we have been thinking quite a bit about this recently. In fact I was just reviewing some figures this morning. To back up a bit, it is true that both Mars and the moon are both mapped to higher resolution and accuracy than the bottom of the ocean -- but that doesn't mean that we care more about the moon. The bottom of the ocean is covered with water -- and Mars and the moon are not. You just cannot see through water very well with electromagnetic signals -- and not with light, not with radar. Because of this, it's not so easy to map the ocean floor very precisely with satellite based instruments like we can for Mars and the moon. So we have to use other instruments -- like sonar -- to map the seafloor. On balance though -- I’ll take having an ocean rather than a planet easy to map from space!

So back to your specific question, we estimate that roughly 40% of U.S. waters have been mapped to some reasonable degree. Here is a paper a collegue presented this year at the Canadian Hydrographic Conference. Here's one RDML Smith wrote for Hydro International earlier this year. One aspect we are adding to this analysis is thinking about not just areas, but the effort it would take to survey the unmapped areas with modern echosounder systems because the coverage rates (area surveyed per unit time) are much higher (scales directly with depth) in deep water than shallow.

But yes, much of the ocean has not been mapped very well. There is an initiative underway now -- Seabed 2030 that aims to fix this. RDML Smith has been more closely involved with this -- so I’ll give him the opportunity to talk to that initiative.

I’ll see if I can tackle both your last two q’s at the same time. Coast Survey’s policy is to use the best available data on the chart -- we ingest whatever data we can use, including scientific data, data from partner agencies, and other crowd-sourced bathymetry. So yes, we use scientific bathymetric mapping for the charts. But often, the best available data we have might be from an old survey we did 60 or 100 years ago. Check out the source diagram on the charts -- for example the lower left or Norfolk chart 12253. While the main channel into Norfolk has been surveyed and charted to modern standards, there are still plenty of soundings on this chart pre-1900! Now most of that data is up the heads of creeks and away from major traffic -- but yes, in many cases, the best available data is pretty old.

EDIT-From Shep: On Seabed 2030...this is an exciting international initiative to challenge ourselves to build and execute a plan to get the ocean mapped by 2030. It starts with locating and using all the data that has already been collected. There are a few international centers that warehouse, archive, and serve up bathymetric data. In the United States, the National Centers for Environmental Information (NCEI) serves this role. We are encouraging crowdsourcing of trackline bathymetry from all vessels, but particularly from those that are multibeam-equipped. We are also promoting the development of disruptive technologies, such as high-endurance unmanned survey vessels, that could make this mission less daunting. Lastly, we are building political support, by assembling a coalition of communities that would benefit from better ocean mapping, and conducting a comprehensive economic study on the value of comprehensive bathymetric data in the U.S. EEZ. Information on that study can be found here.

Hi! Is it true that NOAA paper charts will be changing to metric in the future? If so... why is this happening?


Shep: All of our electronic charts are metric, which is the international standard for ENCs. On most of these charts, the contours are based on the fathom curves, so instead of a 2 meter curve, we would have a 1.8 meter curve. This is a problem for many of our international ships, which have their operational risk management plans specified in metric. Cruise ships, for instance, have their shoal danger alarms set to 10 meters. Since we don’t have a 10m curve, the next deepest curve is 18m (10 fathoms). What happens is that alarms go off when a ship approaches 18m, which is plenty safe water. Going forward, we are going to standardize on metric contours as we build new charts. You may see some existing paper nautical charts switch to metric, but most will stay in traditional units for years to come. Since most users are using our charts electronically, we are focusing our efforts on improving our digital charts. Many navigation systems allow the user to specify the display unit of soundings, so those that are more comfortable in feet and fathoms can continue to use them. Our National Charting Plan has more information about our strategy for making comprehensive improvements to our suite of NOAA navigational products.

Welcome Rear Admiral Smith and Lt. Commander Greenaway,

Does the Office of Coast Survey focus primarily on littoral zone mapping or does your reach extend further into open water?


Shep: Coast Survey's mission/mandate is to survey and chart the entire U.S. Exclusive Economic Zone. We tend to focus the resources we have on coastal waters where depth is a concern for commercial vessels going to and from U.S. ports -- we do support a safe and efficient U.S. Marine Transportation System, after all. But with the Seabed 2030 initiative, the more data we can acquire in deeper waters will help to achieve the globally shared goal to map the world's oceans. We are assembling a coalition of government and commercial ocean mapping interests to facilitate a full mapping effort for our EEZ.

Silly question I'm sure, but can you guys detect every shipwreck on the ocean (plural) floor? It's a leading question, I'm curious about sunken treasure.


Sam: We specifically use systems that are good at detecting objects on the seafloor, including wrecks. But not all wrecks are proud of the seafloor (stand out above), and there is quite a bit of U.S. waters that we have not surveyed. A small wreck (or even a large wreck in deep water) might require a different survey approach than we might use for a typical navigational survey. So I can confidently state that we haven't found them all. Some shipwrecks have archaeological/historical value, so we may not be able to publically release the data if we do find it. Marine archaeologists and treasure hunters have been known to use the same technology we do.

As for sunken treasure, I haven't found any yet, but I am pretty sure that if I do, I won't be able to keep it!

Do you conduct any data fusion from remote sensing data sources to update bathymetric models (for navigation or habitat/other uses)? In my area of Canada, bathymetry is conducted almost exclusively by sonar from boats, but large areas can go unmapped if the shoreline is sufficiently complex. The use of radar or blue lidar (from plane/UAV) could expand mapping efforts especially nearshore, but I understand that this can be prohibitively expensive.


Sam: Yes, we have been looking at all sorts of different methods for augmenting more traditional ship-based work. NOAA is certaintly flying a bunch of coastal topobathy lidar. We are also using satellite image analysis and investigating bathymetry derived from radar observations of waves. And we are now starting to look more at structure from motion. Everything has its advantages and disadvantages, so it's really about finding the right tool for the right situation -- but there is no doubt a tremendous amount of work to be done.

Do you use bathymetric lidar or the new Optech multispectral lidar at all for your elevation data?


Sam: Sure do. Lidar is an important tool for the coastal areas, both topographic and bathymetric. NOAA's Remote Sensing Division (RSD) in the National Geodetic Survey (just a couple floors up from us) plans and executes this work, but we certainly pull that into the charts for shoreline and nearshore updates. We are looking forward to seeing the latest and greatest in lidar R&D at the 2018 Joint Airborne Lidar Bathy Technical Center of Expertise Workshop in Providence, RI, next week.

Have you ever inadvertently mapped an active submarine? If so, were you able to determine what kind/make/model or its country of origin?


Shep: If we ever did, we weren’t aware of it, and certainly could not identify it. We have mapped sunken subs, planes, containers, tires, and lobster pots, in addition to shipwrecks and rocks. We occasionally see things we don’t understand, but they are related to biology (critters) or unusual geology (rocks and muck).

Hello! Questions for Adm Smith:

  1. What is the appropriate ratio of fun sized chocolate bars to survey crew members?

  2. What’s the better port call: Boston or New York?

  3. How do you see the use of crowd-sourced bathymetry and navigation updates as a tool to improve navigational safety in developing countries? Will there be an international body (UN, IHO) acting as a basic quality review team to assist local hydrographers, will there be international best-practice recommendations and restrictions, or will it be solely up to the country of jurisdiction?

  4. Are there any plans in the US or abroad to develop (large) autonomous surface vehicles to survey very remote and hostile parts of the world in service of Seabed 2030?


Shep: Hello! Must be a shipmate! On chocolate. For normal operations, one bag per night will usually do it. On weather days and nights when a number of surveys are being finished up, it can easily triple that!

Boston vs New York. Both great port calls-Boston at the USCG Base, NY at the Intrepid Museum. Boston is right in the North End. Cannoli and great Italian food. History on the freedom trail. In New York, walking distance to Times Square and a dizzying array of cultural experiences. In the end though, I will give it to Boston for the fabulous hospitality of the USCG and the much easier docking.

On crowdsourcing, I think this has a lot of potential. NOAA and the IHO have teamed up to develop a crowd-sourced bathymetry repository under the IHO Data Center for Digital Bathymetry hosted by NOAA. This is just beginning, and we expect much more participation in the coming months and years. The viewer cited above has some basic filtering available, and we are working on better point cloud tools for accessing the data. The IHO Crowdsourced Bathymetry Working Group is drafting some guidance for Hydrographic Offices on use of CSB. In the end, though, it will be up to each charting authority to use CSB in a way that is consistent with their own policies and availability of other data. It is worth noting that we can use CSB to identify areas that need additional surveys or simply to confirm what we think we already know. That alone has a lot of value.

On autonomous survey vessels in support of Seabed 2030, I do know of some technology under development that has big potential to support large ocean mapping efforts, though at this point it is commercially sensitive. It is mostly geared toward efficiency and high resolution, rather than secrecy, so I would not expect it to be useful in hostile (denied) areas. In general, though, each coastal state is responsible for surveying their own EEZs. National laws and concerns vary considerably, and I would expect that availability of coastal data will vary as well. In the US, NOAA is leaning forward aggressively with unmanned systems for hydrography, through our R&D partners, our contract surveying, and our own operations. We expect these systems to be force multipliers for our survey operations in coming years.

What is the best hydro ship in the fleet? Why?


Shep: The one that is working on the day we need it to survey. But seriously, they all have great teams on board, have state of the art technology, and do important work. I will note that Rainier was selected as the Ship of the Year in 2017.

I don’t have any questions in particular but wanted to say hello! I’ve met a couple of your NOAA Corps folks (ones that specifically worked on sea floor mapping) as they rotate through the NMFS lab in my town.


Shep: That is so nice of you -- one NOAA!

Do you have an opinion and/or relationship with OCEANA?


Shep: I think you are talking about Oceana, the foundation dedicated to ocean advocacy. Oceana keeps an eye on what NOAA is doing, e.g. fisheries management and monitoring to protect fish species. We are both committed to making sure regulatory decisions have the scientific backing needed. And Oceana is on the Friends of NOAA list -- supporters who join together to encourage Congress and the Administration to adequately support the agency’s budget.

How accessible is the data you produce? Is it treated like other government agencies like NASA satellite data like Landsat or Modis?Are you able to compare the same area over a period of time?


Shep: Important question! Our data, along with other comprehensive oceanic, atmospheric, and geophysical data is stored at the [National Centers for Environmental Information](ncei.noaa.gov). This data is publicly available. Time series data (in some cases over 25 years) is available for almost all of the datasets. While all of our data is available, it varies in how readily accessible and discoverable it is. We are working on using web mapping services and new cloud technology to improve accessibility to our data. The NCEI data portal for DCDB is a good example.

Do you use your technology to identify living things as well?

There are some awesomely terrifying fish and so many more we haven’t discovered and can’t even bring up to surface level due to pressure changes.


Shep: In Coast Survey, we do not use this technology to identify living things in the ocean. However, others in NOAA - particularly NOAA Fisheries -- do. Scientists can locate fish using sonar technology because a fish's swim bladder also functions as a resonating chamber that can produce and receive sound. Find out more here.

Thank you for taking the time to do this. I'm not in the field but find the questions already asked just fascinating. I expect many younger people will get more interested because of this discussion.


Shep: Thank you for joining us. You can explore more of what we do on our website.

Do you guys use GIS/GIS Analysts often? Any ArcMap at all? And what would someone with just a bachelor's in Geography and a minor in GIS need to do to become involved with programs like this as far as Master's programs go?


Shep: We certainly do. GIS is a huge part of our jobs. Many careers in Coast Survey - both in cartography and in hydrography - require a degree in physical science, engineering, or mathematics that includes 24 semester hours in courses such as geographic information systems, remote sensing, quantitative methods, geography, and statistics. You can find information on our website about employment but also internships.

Do you use any autonomous technology?


Sam: We are certainly working with and developing autonomous technology to survey for depths and obstructions. We have used unmanned underwater vehicles (UUV) for over a decade. More recently we have been working with unmanned surface vehicles (USV), including small (5 feet or so) in operations. We now have a contract in place to convert one of our larger survey launches (28-foot) to be optionally manned or unmanned. Here is an overview of our strategy. One key point: success with autonomous technology needs to be more than just robot-boats. We need to work on autonomous data processing, data telemetry, ways to deploy and recover these systems, and probably most importantly, developing the workforce to work with this new tech.

We are not doing this in isolation. We are working closely with researchers at UNH and USM on autonomous applications. Our contract surveyors also use unmanned systems, as do commercial vendors. Along with the NOAA Office of Atmospheric Research and National Marine Fisheries Service, we have been working with the saildrone systems to investigate applicability for our work. I expect this will be a fast moving field.

Can you explain the cube model a little more?? Need this


Shep: How much time do we have? CUBE is a revolutionary technology for building clean seafloor models from noisy multibeam data. It was developed by Dr. Brian Calder at the University of New Hampshire. The newer version, CHRT, supports variable resolution. http://ccom.unh.edu/theme/data-processing/cube, http://ccom.unh.edu/theme/data-processing/fishpac-lrss-sonar

What's the current annual sea level rise that you are seeing in your surveys? Wondering mostly about the New England area but also curious if it differs on the two coasts. Thanks for doing this.


Sam: Our sister office in NOS -- the Center for Operational Oceanographic Products and Services is in charge of the water level observations, and other good stuff like currents and PORTS

They have a nice page with sea level trends at all the water-level stations. Looks like 2.8mm/ year in Boston.

Important to note that this is local sea level rise, so sinking or rising land factors in. The local sea-level is falling in Juneau, AK, because the land is rising so fast. Conversely, the sea level is rising very fast in Grand Isle, LA, partially because the land is subsiding (sinking).

While exploring have you come across any strange anomalies that required further investigation?


Sam: In almost every survey there are typically a few odd things -- either data artifacts or potential features on the seabed that we go back and have another look at. We might use a different instrument, or a different survey approach. We used to send divers down more frequently to investigate features and ensure we get a least depth, but modern mapping systems are much better than they used to be.

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