Brandy Hill: Weather Reports and Rock Hunting, July 5, 2018

NOAA Teacher at Sea

Brandy Hill

Aboard NOAA ship Thomas Jefferson

June 25, 2018 – July 6, 2018


Mission: Hydrographic Survey- Approaches to Houston

Geographic Area of Cruise: Gulf of Mexico

Date: July 5, 2018


Weather Data from the Bridge

Latitude: 28° 53.4’ N

Longitude: 093° 44.6’ W

Visibility: 10+ NM

Sky Condition: 3/8 (Reminder: 3 out of 8 parts of the sky are covered with clouds.)

Wind: 6 kts


Sea Water: 29.1° C

Air: 27° C


Science and Technology Log

It is fitting to add a section on weather because tonight we are seeing a lightning storm! I can even hear the fog horn. During Bridge Watch, weather data is logged every hour around the clock. Every four hours, it is entered into a computer system. On most days, we are fortunate to get a weather report in various character voices over the intercom from ENS Krabiel.

This is the hourly weather log from June 26, 2018.

My favorite tools are the wind wheel, alidade, and relative humidity thermometers.

A somewhat complicated process allows one to find the true direction (opposed to relative) of the wind. Since the ship is not always traveling North, it is important to be able to calculate true wind direction. Officers typically use a reading on the computer to find true wind direction, but I thought it was a neat tool to try.
The alidade is located outside of the Bridge. It is a sighting device used for measuring angles. It has been helpful with measuring the swell direction. ENS Krabiel mentioned that it is also useful for checking bearings when a ship is anchored. For example, a bearing (like to an oil platform in the Gulf of Mexico) will change if the ship is drifting and/or dragging anchor.
On the Weather Log, there is a place for “dry bulb” and “wet bulb.” This information is collected using two thermometers outside of the Bridge. The dry bulb is a typical thermometer, while the wet bulb has a small sock-like covering wicking up water from a tray. The closer the two temperature values, the higher relative humidity.

I have also sat in on a number of data processing evenings with the Survey Team. In one evening, roughly 50 GB of data from multibeam sonar only was processed. It is estimated that a total of 11 TB has been processed since April. Data processing begins around 7:30 pm and the survey team analyzes all information collected during the hours of 7am- 7pm. Staying on top of processing is important because of the massive amounts that accumulate, especially from side scan sonar.

Julia Wallace, physical scientist, showed me one aspect of processing multibeam sonar. She takes a file of data and runs a “flier finder” with a parameter of 0.5 meters (appropriate for the depth of sonar.) Essentially, the flier finder is marking any outliers that fall outside of this range. Julia then manually goes through and “hides” these points so that they do not contribute to the data set. This is important because when this data is used to mark bathymetry (sea floor depth) on nautical charts, it will somewhat randomly “grab” these false sounding set numbers and could land on one of the outliers, resulting in a false depth.

Every dot in this picture of raw data is a sonar ping returning to the multibeam echosounder. The number of pings depends on the sonar sounding frequency. For example, one could expect 300 pings per second when operating at a sounding frequency of 300 hz.

From what I have witnessed and gathered through multiple conversations with the team, the data collected by the Thomas Jefferson for NOAA charts is extremely accurate. For example, every pixel (or node) on the multibeam sonar grid represents no coarser than 1 square meter of the sea floor. This has changed from about 30 years ago where the ratio was 1 nodel: 5 square meters. In addition, many processes are doubled-up as a check for validity. This includes crosslines for checking main scheme data and operating two multibeam frequencies at the same time.

One of the benefits to running two frequencies of multibeam is the ability to create an overlapped average of the two backscatter signals (with a false color scheme.) This information helped inform Lt. Anthony Klemm and survey technician Kevin Brown determine eight unique sites varying in backscatter intensity for bottom sampling. (Remember: intensity is a measure of how strong the sonar ping returns, depicting varying sea floor substrate.

The use of this technology paid off! All eight sites sampled varied in texture and sediment size. Using this process of selectively choosing sites of interest based on “multispectral” backscatter intensity has replaced taking numerous random bottom samples using a grid. Again, this is a highly accurate and time-saving process. It was also interesting seeing the actual sea floor that we are mapping.

In the bottom right corner, Bottom Sample #1 site is selected.



 CHST Allison Stone manages the crane while Lt. Charles Wisotzsky directs the bottom sample claw and ENS Taylor Krabiel performs various substrate tests. 

ENS Krabiel gives me a tutorial on bottom sampling. Krabiel enjoys creating short “Rock Hunting” clips for entertainment. His enthusiasm has made this trip a lot of fun.
All of the eight bottom sample sites had a different composition. One in particular had a lot of rocks and shells. The rock in the upper right appears to have remnant tunicate casings.
Notes from survey sheet H13044, BS# 001 (Bottom Sample #1) state the grain size: silt, muddy, coarse, and some shell fragments.

A GoPro is located in a cage on the bottom sample claw. Video footage of the sea floor enables hydrographers to view the substrate and current ripples in the sand. ENS Krabiel wears the control on his wrist to activate the camera.

Personal Log

 I have enjoyed hearing the back-stories of the crew. For example, Allison Stone, Chief Survey Technician knew she wanted to be a part of NOAA when she was in 6th grade- the same age as my students. She remembers going to a parent career night at school and speaking with a presenter from NOAA. The presenter was enthusiastic about their job which inspired Allison to pursue a placement with NOAA. Although she envisioned counting marine animals and snorkeling daily, she is still passionate about her work in hydrography geoscience and speaks highly of NOAA outreach.

Field Operations Officer, Lt. Anthony Klemm started out wanting to do a public service and became a teacher. Later, he joined the NOAA Corps and after completing basic training got a job at the Marine Chart Division in Washington DC. It was during this time that he was given a lot of flexibility and time to create and test his own ideas and experiments. In his words, some of them flopped. However, one idea that has recently captured attention is the idea of “crowdsourcing” bathymetry. Collecting, processing, and submitting data for the official approval and update of NOAA nautical charts is a long process. It can take months for charts to be updated and available to the public. Crowdsourcing bathymetry is a way for the general public to gather and submit sonar data using simple devices like a “fish finder” that one might find on a recreational boat. These could serve as interim bathymetry data until the areas can officially be surveyed and charted. It’s also simple (users select a setting), and free.

Visit the NCEI/IHO Data Center for Digital Bathymetry  to view digital bathymetry data.

You can read more about this program at:

active captain shoaling hazard fl 2.PNG

This photo and thee above are snapshots of data collected using “crowdsourced” bathymetry.


+ Participated in a simultaneous medical/fire drill.

“This is a drill, this is a drill. There has been a medical emergency on the starboard stairway of the bridge…” The person in this picture is only acting and not actually injured. The bridge had also simulated a fire which interfered with steering and communications.
A debrief was held in the Mess after the drills.
This was a day for drills. The FRB (Fast Rescue Boat) was manually unloaded using a hand brake to simulate loss of power. Earlier in the day, the launch boat was manually loaded back onto the ship. Passengers (including myself) boarded the ship using a rope ladder.



2 Replies to “Brandy Hill: Weather Reports and Rock Hunting, July 5, 2018”

  1. Brandy, you have done such a great job of educating us about the Hydrographic surveys. Thank you ! Your students will gain much insight by your experiences that you share. Great blog !

  2. The surface of the sea and the condition of the sea waves very much affect the weather conditions. It was quite good to know about these weather reports. Learned a lot from this regarding how it can be recorded and the process. Keep sharing this more and more!
    Shallow water survey

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