Subscribe to Diving Deeper

Ocean Service Feeds

What is a Podcast?

A podcast is a an audio file published on the web. The files are usually downloaded onto computers or portable listening devices such as iPods or other players.

Read more about podcasting from

Find other podcasts from the US government

Diving Deeper: Safe Navigation

Episode 39 (June 21, 2012)

HOST: Welcome to Diving Deeper where we interview National Ocean Service scientists on the ocean topics and information that are important to you! I'm your host Kate Nielsen.

Today's question is...What resources do ship captains and boaters need to safely navigate our nation's waters?

NOAA's Office of Coast Survey is responsible for developing a suite of navigation products and providing services that ensure safe and efficient maritime commerce.

Today we will talk with Rachel Medley on safe navigation and some of these products that are out there for our boaters. Rachel is the Acting Chief for the Customer Affairs Branch within NOAA's Office of Coast Survey. Hi Rachel, welcome to our show.

RACHEL MEDLEY: Hi Kate, thank you so much for having me. This is really exciting. This is my first podcast I've ever done, so I hope it goes well.

HOST: I'm sure it will. Thanks for being here. So Rachel, let's start right off with what are some of the main tools that mariners need for safe navigation?

RACHEL MEDLEY: Well, they certainly need a chart and preferably an up-to-date chart. Now we have charts here that are both electronic and paper form, so everybody get your chart.

HOST: Can you briefly explain the difference between a chart and a map? We've heard this in some past episodes, but just to get everybody on the same page.

RACHEL MEDLEY: My family frequently asks me this question as well because I always correct them and say it's not a map, it's a chart. So, a map as many people know is just a two-dimensional representation of spatial relationships in three-dimensional space. A chart goes a little bit further than that. It's essentially a map, but it has more information and symbology for a specific purpose such as navigation.

HOST: And, why does a boater need a nautical chart then? And how does somebody get a nautical chart?

RACHEL MEDLEY: Two great questions, one that we frequently field from our office. I'll answer the first one, boaters need nautical charts to avoid grounding. They don't want to run aground somewhere. Also, a lot of times in different navigational waters there might be, particularly for small craft boats, for recreational boaters, there are restricted areas. These might be restricted for naval firing ranges or perhaps sanctuaries. Now there's hefty fines that can be incurred if you go into these areas, not to mention, some of them are potentially very dangerous, so you would want to consult your nautical chart to make sure that you're not navigating in there. But moreover, a nautical chart is mostly useful for safe navigation for yourself and for the other boaters around you.

So that's why you need a nautical chart. Now, how do you get a nautical chart? You can go to our website and we have links to where you can acquire paper charts, electronic navigational charts, we have historic charts, we pretty much have every product that you might be looking for and to suit different boater needs. You might not need all of the electronic suite, but you could be really interested in one particular product that we have to offer.

HOST: So there's no excuse for those of us that are out on the water, that we can get the chart that we need through so many different means. So, I mentioned this briefly in the introduction that I gave to folks, but can you expand on the role of your office, the Office of Coast Survey, in supporting safe navigation?

RACHEL MEDLEY: OK. So, of course we update the charts, we create all of the nautical charts that you find everywhere. We also update them with any sort of critical information. We have print-on-demand, various different products that we create. We also do all the hydrographic surveys, which means that we're collecting all of that sea floor data and then applying it onto the chart. We also coordinate with a lot of other agencies, primarily the U.S. Coast Guard, to ensure that the most up-to-date information is flowing to our customers and that it's getting applied to the chart, for critical items anyway, that they're getting applied to the chart in a very timely manner.

HOST: Rachel, I've seen several reports over the last year about NOAA's survey vessels responding to different navigation emergencies. Can you tell me a little bit about this?

RACHEL MEDLEY: Sure. We actually have survey vessels, we have both small boats and several hydrographic ships, that are strategically placed around the country that can mobilize quickly and leave off surveying temporarily to deploy to the requested emergency area.

I can give a specific example. This recently happened during the 2011 hurricane season with Hurricane Irene. If you recall this is a slightly unusual hurricane track that actually impacted the Mid-Atlantic and some regions in the Northeast, not very typical of hurricane season for us. And our survey teams were able to get to the, specifically the Norfolk and Hampton Roads area within several hours of receiving a request from the U.S. Coast Guard captain of the port and they began survey operations there. This ultimately resulted in the removal of shipping restrictions and resumed commerce in the area, which certainly was a great relief to the local maritime community and the port authority, who is in charge of everything. So we definitely do a lot of emergency response activities in addition to our regular survey activities.

HOST: So Rachel, we talked with Tom Loeper from your office back in 2009 about nautical charts, but maybe you can help remind folks who haven't heard that episode about some of the basics. First, who uses NOAA's nautical charts?

RACHEL MEDLEY: Well, definitely commercial shipping uses our nautical charts and recreational boaters frequently use all of our nautical charts.

HOST: OK, so the products then are critical in both that commercial/industrial realm and by recreational boaters?

RACHEL MEDLEY: Yes, certainly. Industrial and commercial shipping, they're required to utilize our charts when they come into port. They typically navigation using electronic navigational charts on their display boards, but they have to also possess a paper copy on board and the Coast Pilot, and this is required by the U.S. Coast Guard.

For recreational boaters that I talk to, they use both the electronic navigational charts and the paper charts. There's definitely a split and a divide between those who really love electronic and those who really love paper. But the key issue here is that you should have the updated version of either, whichever one you choose. And this will help to ensure that you're navigating safely. In terms of actually utilizing a chart beyond just safety and navigation, I've talked to a lot of fishermen as I've gone to a lot of outreach events and boat shows, and they love to use the navigational charts for clues to look for great fishing areas. These clues could be drop-off areas, bottom type, fish havens, all of these sort of symbologies are represented on our charts. So you can use them not only to safely navigate, but also to accomplish whatever you're out there to do.

HOST: So Rachel, if I have a chart, maybe especially a paper chart as we're talking about, can I keep it, and more importantly, can I use it forever?

RACHEL MEDLEY: OK, so this is a two-part answer here. You can certainly keep it forever. When I look at a chart, I think it's just such a beautifully crafted document. I actually have a chart of the Potomac, because I live in Washington, D.C., mounted on my wall at home, so I think it's beautiful. Now, I wouldn't use that chart for navigation because it's not been updated. So, just like your car GPS has maps in it that need to be updated and refreshed to make sure that you're safely driving on the roads that you're meant to be driving on, a nautical chart has the exact same stipulations. You should always check, you can check our website to see if you have the most current version of the nautical charts or if there's any critical updates that have been applied to that chart, so when you go out, you should just make sure that you have the most up-to-date nautical chart. But certainly, you can keep our charts and you can do other fun things with them, but the most up-to-date one needs to be utilized for navigation.

HOST: And I can see that there might be new roads or something like that and why folks might need to update their GPS, but why are charts updated? What kind of changes are happening out in our coastal waters that require these updates?

RACHEL MEDLEY: Right. So the sea floor is constantly changing of course. But even more than that, charted information that we have, some of it is actually of a vintage from the 1800s and those are lead line surveys. Now, we've gone back and resurveyed a lot of those areas. And we've found that those soundings that are on the charts from those lead line surveys are actually accurate. But there's still a lot of unknown information in between the soundings such as obstructions that might be harmful to boaters. As Coast Survey continues to acquire data from our hydrographic ships, we update these older vintage areas with new high resolution soundings, therefore ensuring the best possible charted information.

HOST: So Rachel, back to a few of our basic kind of questions that we were on a roll with. How many charts do we have, and do these charts cover the entire U.S.?

RACHEL MEDLEY: Well, yeah they do. Coast Survey has actually been the nation's chart maker for over the last two centuries and because of that we have over 1,000 charts in our inventory that we've made and that we maintain. They actually cover all of the U.S., the U.S. territory coastal waters, and the Great Lakes. However, we do not chart rivers and inland lakes.

Now that is not to say, you said, do these charts cover the entire U.S. Yes, they do, but that's not to say that they're all at the same level of detail. Now, scale is something that's very important to think about when you're looking at a chart. Some of our charts are very large scale. They can be 1:20,000/1:5,000 meaning that you've got a lot of detail in that one chart. But we have other scales and other charts out there that are 1:1,000,000 meaning that you're not going to get as much information on your chart. So, you just really have to look at the chart scale and understand what that represents whenever you're navigating.

HOST: Why is that some of these charts have such different scales?

RACHEL MEDLEY: So, that's a great question too. Some of the scales, where we see really small scale charts, like a 1:1,000,000, that might be something up in Alaska where it's representing a bit more offshore, we don't have that much survey data information yet, we're certainly trying to get to it, but Alaska's pretty far, and those charted soundings that we have, a lot of them were lead line soundings, if you can imagine that, up in Alaska, 1800s, mid-1700s. There was a chart that was able to be created to represent that area, but we're working hard to be able to get more survey information to build more detailed charts.

HOST: And when you say soundings, is that like the depth information on a chart?

RACHEL MEDLEY: That is the depth information, right. The soundings that are applied to the chart are taken from that vast amount of soundings that we collect through the hydrographic survey and we select soundings that are the least depth sensitive and what those soundings are based on, they're relative to the mean lower low water height at the surface down to the bottom of the sea floor. So a sounding is that depth measurement from the mean lower low water line to the sea floor and that's the number that's being represented on the chart. And a sounding could be in feet, it could be in meters, it could even be in fathoms, so when you look at a chart, also make sure that you understand what sort of units you're looking at when you see a sounding. And those will just be the numbers, it will be represented at that point by a number, and that's the depth of the sea floor at that point.

HOST: Thanks for clarifying what the sounding information was and something else that I guess we might also see on our charts is something you've mentioned a few times today which are obstructions and I've also heard of things like obstacles to navigation. What are some common obstacles to navigation?

RACHEL MEDLEY: OK, so we normally refer to them as obstructions typically, but this could be rocks, wrecks, pipelines that you might find. A particular example is in the Gulf, you might see a derelict oil platform. Certainly during Katrina in 2005, we saw a ton of changes happening on the charts with new obstructions and charted debris in the area, so really when you talk about an obstacle or an obstruction to navigation, it could be anything, it could be manmade or it could be naturally derived.

HOST: So, how about something in our water that's mobile, something such as marine life, maybe whales for example. Are they considered to be an obstacle to navigation or are there ways that we can inform or warn mariners and boaters of large marine animals?

RACHEL MEDLEY: Well, I can give an example of something that we did several years ago. We knew that the Atlantic right whale was endangered and the Office of Coast Survey through collaboration with other NOAA partners, we actually rerouted all of our shipping lanes up in the Boston area to be able to better accommodate the migration patterns of the right whale. And so that's something that Coast Survey is very sensitive to and we're aware of the impact that shipping can have on whales and we try and do our best to mitigate that impact.

HOST: Great, thank you. So Rachel, what is the greatest challenge then in producing nautical charts to help keep mariners safe?

RACHEL MEDLEY: So, I think one of the things I've recently touched on in this interview is that the vast majority of our surveys are still of a vintage that pre-dates modern sonar techniques. And, we're working very hard to get to all those areas, while also resurveying critical areas for the shipping industry. With the advent of modern sonar techniques, we've gone from what use to be just a few hundred soundings per survey to a few hundred thousand or million soundings or even more per survey, so that's a lot of data.

And, we have a really thorough quality control process and it just takes a very, very long time to sift through all of that. And, if you can imagine, not only cleaning up all the data, getting it right, but then applying all that and selecting out just a few soundings from all that data, that hundreds of thousands of soundings that make it out onto our chart. So, that's one of our biggest issues is that it takes a lot of time. And we've got very, very good, meticulous cartographers that work at the Office of Coast Survey that have to really work hard to get that done.

HOST: So Rachel, my last question for you today, do you have any final, closing words for our listeners?

RACHEL MEDLEY: Just a couple things about our products. A lot of our products are free. Many people are surprised to learn that Coast Survey collects all of the survey data that you would see, and in addition to maintaining the charts. So we collect all this data and it's utilized for the nautical charts, but it's also free and available to the public. This is really high resolution, wonderful data that the public has access to as well.

One other thing I'd like to mention is I know that we talked about a lot of these things being available on the website, well, not everybody is pro-website or they feel like their questions aren't being directly answered by navigating through the website and that's perfectly understandable. One of the nice things and services that we also provide is, we have a hotline, where you can actually talk to a real live person and they will answer your nautical questions. That number is 1-888-990-NOAA, so it's 1-888-990-6622. And, in addition to that, beyond just this hotline, we also have regional navigation managers that are strategically placed throughout the coastal U.S., Alaska, and Hawaii. So, if you want to talk to someone local, you certainly are able to. You can contact one of them and they'll be more than happy to help you because I know a lot of people have local questions that are very specific and it might be tricky to find that on the website, but these navigation managers can really help. Either they'll answer the question themselves or they will know the person that will be able to answer your question.

HOST: Great, thanks Rachel, thanks for sharing that personal connection that folks can have. That's really good to know.

RACHEL MEDLEY: Yeah, I know I certainly appreciate when I can talk to somebody face to face or on the phone.

HOST: Thanks Rachel for joining us today on Diving Deeper and talking about safe navigation. To learn more or to gain access to a nautical chart in your area, please visit

That's all for today's show. Please join us for our next episode in two weeks.