1. “Mind the rudder, or meet the rock”
Identification and Depiction of
Submerged Rocky Features in HCells
for Application to NOAA Charting Products
Cathleen Barry, NOAA Pacific Hydrographic Branch
Kurt Brown, NOAA Pacific Hydrographic Branch
Peter Holmberg, NOAA Pacific Hydrographic Branch
Sean Legeer, NOAA Marine Charting Division
David Neander, NOAA Pacific Hydrographic Branch
Gary C. Nelson, NOAA Pacific Hydrographic Branch
Keith Toepfer, NOAA Pacific Hydrographic Branch
Toshi Wozumi, NOAA Pacific Hydrographic Branch
“Mind the rudder, or meet the rock”
Quoted by Capt. Fatty Goodlander
Capt. Gary Goodlander is a marine journalist who circumnavigated the earth in a 38’ sloop. He refers to himself as “the salt-stained sea gypsy” .

2. WHAT DO WE DO AT PHB? What do we do? We produce HCells!
What is an HCell?
An S “base cell file” containing all of the new survey and chart information necessary for updating or creating a new ENC and raster chart product.
HCell

3. OUR ALASKA WORK AREAS
Southwest, South central and Southeast Alaska

4. WHY ARE ROCKS AND ROCKY AREAS A CONCERN FOR PHB?
The switch from Single Beam Echo Sounders to use of Multibeam and Lidar flooded PHB with more features to process than ever before.   
Lidar rock features against chart 17405, 1:40,000.
This view shows 737 Lidar rocks and 8 Lidar islets.

5. THE ISSUES & THEIR SOLUTIONS
TWO ISSUES…
PHB identified two distinct aspects to the problem:
(1) Improper characterization of rocky features, and inconsistent characterization between field units.
(2) An overabundance of rocky features from Multibeam and Lidar surveys;
TWO SOLUTIONS
(1) Standardization of Practices—Define parameters for ledges and reefs, rocky foul areas, and rocky seabed areas. Distribute guidance to our in-house surveying units and contractors.
(2) Reduction in the Number of Individual Rock Features—Generalize areas with numerous discrete rock point features into foul and rocky areas.
OUR GOAL
Reduce ping to chart time and improve the chart product for multiple users

6. STANDARDIZED DEFINITIONS
Ledges and Reefs: Intertidal (MHW to 0)
Foul areas: Offshore of 0, to a depth where most rocks become submerged
Rocky seabed areas: In depths where most rocks are submerged
rky
12.2 Rk 38 32 49 19 12 65 18 11
ledge
foul with rocks
rocky seabed area
rock is high point of ledge
MHW
MLLW “0”
foul limit
mostly submerged rocks
mostly exposed rocks
islet is high point of ledge 17

7. STANDARDIZED DEFINITIONS
rocky seabed
reef
foul
rky
rocky seabed
ledge
Raster Chart
ENC

8. THE ISSUES & THEIR SOLUTIONS
TWO ISSUES…
PHB identified two distinct aspects to the problem:
(1) Improper characterization of rocky features, and inconsistent characterization between field units.
(2) An overabundance of rocky features from Multibeam and Lidar surveys;
TWO SOLUTIONS
(1) Standardization of Practices—Define parameters for ledges and reefs, rocky foul areas, and rocky seabed areas. Distribute guidance to our in-house surveying units and contractors.
(2) Reduction in the Number of Individual Rock Features—Generalize areas with numerous discrete rock point features into foul and rocky areas.
OUR GOAL
Reduce ping to chart time and improve the chart product for multiple users

9. REDUCTION IN FEATURES
H11350, Eastern Prince William Sound, Galena Bay

10. EXAMPLES OF ROUGH OR ROCKY SEAFLOOR AREAS
H11350, Eastern Prince William Sound, Galena Bay, Valdez chart 16707, 1:40,000

11. EXAMPLES OF ROUGH OR ROCKY SEAFLOOR AREAS
H11391, Port Bainbridge, Prince William Sound, Alaska, chart 16702, 1:40,000

12. EXAMPLES OF ROUGH OR ROCKY SEAFLOOR AREAS
H11391, Hogg Bay, Port Bainbridge, Prince William Sound, Alaska, chart 16702, 1:40,000

13. EXAMPLES OF ROUGH OR ROCKY SEAFLOOR AREAS
H11391, Swanson Bay, Port Bainbridge, Prince William Sound, Alaska, chart 16702, 1:40,000

14. EXAMPLES OF ROUGH OR ROCKY SEAFLOOR AREAS
Approaches to Newport, Oregon, detail of reef near channel entrance.

15. EXAMPLES OF ROUGH OR ROCKY SEAFLOOR AREAS
Approaches to Coos Bay, Oregon, Gregory Pt, Baltimore Rk and Mussel Reef.

16. DELINEATING ROCKY SEABED AREAS FROM SURFACES
Multiple single resolution surfaces with all color ranges altered to 1.33 – m
Combined Surface color range 1.33 – m

17. DELINEATING ROCKY SEABED AREAS FROM SURFACES
The rocky seabed may be delineated by the hydrographer or cartographer, and navigationally significant rock features may be selected.
6.46
4.8

18. EXAMPLES OF DELINEATED ROCKY SEABED AREAS

19. EXAMPLES OF DELINEATED ROCKY SEABED AREAS
H11392, Port Bainbridge, Prince William Sound, Alaska, chart 16683, 1:40,000

20. THE “SHALLOW SURVEY 2008” PROJECT
PHB created an HCell with rocky seabed areas using the Reson Shallow Survey 2008 dataset
Shallow Survey 2008 HCell

21. BUILDING THE SHALLOW SURVEY 2008 HCELL
New Hampshire’s rocky terrain is similar in some respects to SE, SW and South Central Alaska

22. ROCKY NATURE OF SHALLOW SURVEY SEABED IS CONFIRMED IN CARIS HIPS
2-D slice, CARIS HIPS subset editor, showing rocky terrain

23. BUILDING THE SHALLOW SURVEY 2008 HCELL
Shallow Survey 2008 data set against Portsmouth Harbor chart 13283, 1:20,000, Chart soundings in feet, HCell soundings in meters

24. THE COMPLETED HCELL IN CHART UNITS
The completed HCell in charting units (feet), with depths, rock point features (for high points only), rocky seabed area objects and bottom characteristics (copied from the ENC).

25. THE HCELL APPLIED TO THE ENC
The completed HCell applied to the ENC, soundings and heights in feet.

26. QUESTIONS ?

27. EXTRA SLIDES

28. CONCLUSIONS
Rocky seabed topography of Alaska and the Pacific coast is recognizable in navigation surfaces.
Identification and delineation of rocky seabed areas at the earliest stage of processing in the field is encouraged if it will save time in the field.
If the practice is adopted to apply rocky seabed areas to the chart it should be for all surveys in a region. (To avoid the dangers of a lack of rocky seabed areas appearing to indicate the absence of rocky features to the mariner.)
Before these practices can be wholly implemented, more guidance is needed.
Some considerations for which parameters may be appropriate are:
Is the surface rocky (lumpy) or is it hard?
What is the scale of the chart being compiled to?
How well defined is the feature?
What is the density/concentration of submerged rock features in the area?
What is the height of a submerged rock relative to the surrounding seafloor?
What is the distance of a submerged rock from a nearby feature of similar or lesser height;
What is the bathymetric coverage in the area (size and proximity of data gaps)

29. WHAT IS THE ROLE OF PACIFIC HYDROGRAPHIC BRANCH?
At PHB, we work with NOAA Ships Fairweather and Rainier, and contractors, too.
Ship’s personnel acquire data and package it up as depths (surfaces) and features for PHB.
PHB prepares the survey materials for application to the chart. (We create HCells.)
Marine Charting Division uses the materials provided by PHB to update the ENC and the raster charts, or creates new charts.
US West Coast and Alaska
Seattle, Washington
Silver Spring, Maryland