Scaled photographs of surf over the full range of breaker sizes on the north shore of Oahu and Jaws, Maui, Hawaiian Islands (NODC Accession 0001753)

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Frequently anticipated questions:


What does this data set describe?

Title:
Scaled photographs of surf over the full range of breaker sizes on the north shore of Oahu and Jaws, Maui, Hawaiian Islands (NODC Accession 0001753)
Abstract:
Digital surf photographs were scaled using surfers as height benchmarks to estimate the size of the breakers. Historical databases for surf height in Hawaii are recorded in Hawaii Scale Feet (HSF), and these photographs have been used to translate HSF to trough-to-crest heights. Results show the trough-to-crest heights to be double the HSF within a 10-20% margin of error over the full range of possible breaker sizes. This assumes 1) the trough- to-crest height is defined as the highest height reached in the vertical between the crest and the preceding trough at any point along the wave front during breaking and 2) zones of high refraction on outer reefs are included for extreme days when Waimea Bay was the reporting location.
Supplemental_Information:
Entry_ID Unknown Sensor_Name digital cameras Originating_Center NOAA/NESDIS/NODC/NCDDC Storage_Medium jpeg Online_size: 9190 kbyte

Resource Description: NODC Accession Number 0001753

  1. How might this data set be cited?
    Patrick Caldwell - NOAA/NESDIS/NODC/NCDDC, Unknown, Scaled photographs of surf over the full range of breaker sizes on the north shore of Oahu and Jaws, Maui, Hawaiian Islands (NODC Accession 0001753): None None, Unpublished Material, Unpublished Material.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -158.108
    East_Bounding_Coordinate: -156.323
    North_Bounding_Coordinate: 21.692
    South_Bounding_Coordinate: 20.950
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 28-Jan-1998
    Ending_Date: 24-May-2004
    Currentness_Reference: ground condition
  5. What is the general form of this data set?
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
    2. What coordinate system is used to represent geographic features?
  7. How does the data set describe geographic features?
    Entity_and_Attribute_Overview:
    A summary of files is given in ../../data/readme.txt

    The scaled photographs are sorted by size in Subdirectories, which have names as xx_Hsf or xx_xx_Hsf, where xx denotes a size and xx_xx denotes a size range.

    Within each subdirectory, filenames of each photograph vary yet all contain the date (mmddyy) and the recorded size in the Goddard-Caldwell dataset as _Cxx, where xx is the size in Hsf.

    Entity_and_Attribute_Detail_Citation: none

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
  2. Who also contributed to the data set?
    Hawaii Liaison Office National Coastal Data Development Center NOAA/NESDIS/NODC/NCDDC
  3. To whom should users address questions about the data?
    Mr. Patrick C. Caldwell
    NOAA/NESDIS/NODC/NCDDC
    Hawaii/US Pacific Liaison
    1000 Pope Road, MSB 316
    Honolulu, Hawaii
    USA

    (808)-956-4105 (voice)
    (808) 956-2352 (FAX)
    caldwell@hawaii.edu
    Hours_of_Service: 8 AM to 5 PM weekdays
    Contact_Instructions: check services@nodc.noaa.gov if not available

Why was the data set created?

To better understand wave heights reported in Hawaii Scale Feet.

How was the data set created?

  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
    Date: Unknown (process 1 of 1)
    Surf Observations ================= With the growth of surfing in the 1960s on the north shore, Oahu, came routine observations made by surfers, and later in the 1970s, by lifeguards and commercial surf report ventures. Observations were reported in Hawaii Scale Feet (HSF).

    Observations are reported as a height range. Observers ignore the smaller waves. As a simplified example, assume a given day has dominant wave energy in the 14-17 second wave period range with negligible energy outside this band. Assume five waves catch the eye of an observer every four minutes, or 100 waves every 80 minutes. This takes into account the time periods of varying length without waves arriving. The upper end of the reporting range is approximately equivalent to the H1/10, the average of the highest 10 waves, which if evenly distributed in time, would occur every 8 minutes. The lower end of the observing range is near the H1/3, or the average of the highest 1/3 waves, which if evenly distributed in time, would occur every 3 minutes. The highest wave over this nominal 80-minute period with 100 waves, or H1/100, would be equivalent to the observer's use of "occasional" heights in their reports.

    A digital database of surf observations, referred to as the Goddard-Caldwell (GC) set, dates back to August 1968 for the north shore, and to March 1972 for the south shore of Oahu. It is described in more detail in Caldwell (2005). Data are recorded in HSF. The daily values in the GC database refer to the surfing location along the given coast with the highest reported breakers. For the north shore, most observations are taken at Sunset Point, which is usually one of the highest surf spots along the coast under the dominant northwest swell direction. For days of extreme surf with heights greater than roughly 15 HSF, visual observations are reported at Waimea Bay, where breakers are much closer to shore relative to most of the north shore, which is fringed with offshore reefs. The surf reports are typically made several times per day. The daily value in the GC set represents the upper end of the reported height range for the observing time with the highest breakers. This number aims to be equivalent to H1/10. Comparisons of the GC database to 1981-2002 data from NOAA buoy 51001, which is located roughly 400 km west-northwest of Oahu, show the surf observations are temporally consistent with the shoaling-only, buoy-estimated breaker heights and have an uncertainty of 10 to 15% of the surf height (Caldwell, 2005).

    Photograph analysis =================== A breaker or surf is defined at the moment in time when some portion of the front face of a wave becomes vertical and unstable due to a decrease in water depth. The trough to crest surf height is defined as the vertical distance between the crest and the preceding trough at the moment and location along the wave front of highest cresting, which has been shown in models and observations to be at the time and location of breaking. For locations with high refraction, such as Sunset Point, where most of the visual observations are made, the breaker often forms an A-shape. The trough to crest height refers to the center of the A, i.e., the point along the wave front with the highest height.

    Photographs were obtained from Internet sites or directly from photographers. Location and date was a prerequisite. Photographs showing the highest waves of a given day were chosen from the available pool of pictures. Pictures were sorted by size in HSF matching the date to the GC database. Typically, 15 images for each size category were selected (Table 1).

    Each photograph requires a surfer or some other identifiable object to use as a benchmark in estimating wave height. Dashed lines were superimposed on each photograph to indicate the approximate trough and crest. An arrow was overlaid next to each benchmark to denote a 5' unit. The benchmark arrow was duplicated and subsequent arrows were stacked from trough to crest to gauge the wave size (Figure 3).

    Photographs capture a two-dimensional image of a three-dimensional world and distortions of shapes and sizes are inherent. Shots taken from a high vantage point, such as a cliff or helicopter, make detection of the wave trough difficult. Wave size is distorted in pictures taken by a swimming photographer near the surfer. Priority in selecting shots was given to images taken by a photographer standing close to mean sea level either on shore or on a floating craft. Distortion of perception decreases as the distance between the camera and the surfer/wave increases.

    There are various sources for errors in this exercise. The error associated with trough identification has been estimated at 10% of the wave height. The surfer's height is not known in most images. It is assumed that the average surfer height is 5'9" and a typical surfer stance is roughly 5' with a 6" uncertainty, which leads to an error of 10% in the surf height estimate. For both cases, the errors average out as the number of photographs increases. Since the photographs were selected from still images, it is not certain that any given picture represents the highest height reached by that wave during breaking, or if these few select waves represent H1/10, which is assumed in the GC database. With the small number of available pictures per day, the translation based on these pictures likely underestimates the heights in the GC database.

    Each scaled photograph was examined to estimate the height to the nearest tenth of a foot. For each size category, a mean and standard deviation of the estimated trough to crest heights were computed (Table 1). Using two standard deviations as a proxy for uncertainty, the margin of error is within 10-20% of a given size for categories with at least 15 photographs, disregarding the lowest and highest percentage values. For days with surf heights of 15 HSF or less, most photographs are taken at spots from Log Cabins to Sunset Beach, which typically has the highest surf on the north shore (Figure 2a). For days with surf heights greater than or equal to 15 HSF, photographs were further sorted by location: Waimea Bay, Oahu outer reefs, and Jaws (Peahi), Maui. Under northwest swell with 17-20 second wave periods, the travel time from Oahu to Maui is roughly three hours, which makes comparisons of daily data appropriate. Fewer photographs were available for the Oahu outer reefs than for Waimea Bay. The paired HSF and trough to crest heights are plotted in a scatter diagram (Figure 4).

    For surf heights of two to six HSF the translation shows the trough to crest heights are more than double the HSF observations (Table 1, last column). From six to twelve HSF, the translation is close to double. An inadequate supply of photographs were available of Sunset Point for heights in the 13-15 HSF range, when the offshore-most breaking point is roughly one km from shore and strong currents impede water photography. The available images suggest the translation of 15 HSF to trough to crest heights is slightly less than double. For the entire range from two to fifteen HSF, the translation can simply be defined as double within the margin of error.

    For surf above 15 HSF, the wave energy at Sunset Point becomes overwhelming and the resultant breakers occur unpredictably over a wide area both parallel and perpendicular to shore. This makes surfing dangerous due to difficulties in maintaining a safe wave-entry point. Under such extreme conditions, surfers historically challenged Waimea Bay, where the take-off zone is narrower and the proximity to shore allows landmark referencing for more precise wave-entry positioning.

    Numerous photographs are available for Waimea Bay during surf in the 12-30 HSF range. The surfers enter the wave about 50-100 m outside the point on the northeast side of the bay and surf at an angle toward the safety of the deep waters in the center of the bay. The wave-entry point shifts northwest of the northeast point of the bay with increasing wave size. At approximately 30 HSF, the entire wave front cascades nearly simultaneously across the breadth of the bay, ending a surfer's chance for a safe ride.

    The photographs at Waimea Bay suggest the trough to crest heights are roughly 1.5 times HSF during days with observations in the 15-30 HSF range. Within the collection of photographs, there are several occasions when images were available for the same day from both Waimea Bay and outer reefs of Oahu and Maui, where tow-in surfing (motor-powered-watercraft-assisted breaker entry) has gained popularity over the past decade. Over the submerged ridges of the offshore reefs to either side of Waimea Bay, the SWAN output (Figure 2b) shows increased heights due to convergence of wave rays, i.e. refraction. Photographs of tow-in surfers on outer reefs validate the larger heights relative to Waimea Bay.

    In summary, the translation of HSF to trough to crest heights is a factor of two within the 10-20% margin of error for the full range of breaker sizes encountered in Hawaii. This assumes the height is defined as the highest height reached in the vertical from the trough to crest at any point along the wave front during breaking and zones of high refraction (outer reefs) are included for extreme days when Waimea Bay was the reporting location. The HSF, or simply dividing trough to crest height by two, has been adopted by other big wave enthusiasts around the globe as seen in pictures and dialogue from extreme surf contests in California, Peru, and South Africa. It is important for scientists and the general public to understand this relationship for utilizing surf observations reported in HSF.

    Acknowledgments. Larry Goddard is recognized for establishing the surf observation database from 1968-87. Great appreciation is given to the north shore surf observers, surfers, and photographers. Special thanks are given to photographers Claudia Ferrari (claudiaferrari.com), Jamie Ballenger, (HawaiianWaterShots.com), and Ian Masterson. Warm regards go to photographers of Oahu outer reefs (Justin Langlais, John Bilderback, and Hankfotos.com) and Jaws, Maui (Eric Aeder, Steve Kornreich, Les Walker, C. Levy, and C. Oreve). Person who carried out this activity:

    Mr. Patrick C. Caldwell
    NOAA/NESDIS/NODC/NCDDC
    Hawaii/US Pacific Liaison
    1000 Pope Road, MSB 316
    Honolulu, Hawaii
    USA

    (808)-956-4105 (voice)
    (808) 956-2352 (FAX)
    caldwell@hawaii.edu
    Hours_of_Service: 8 AM to 5 PM weekdays
    Contact_Instructions: check services@nodc.noaa.gov if not available
    Data sources used in this process:
    • Caldwell, P. and J.Aucan, 2004: Translation of surf observations from Hawaii
    • scale to trough to crest heights based on photographic evidence. Poster. 8th
    • International Workshop on Wave Hindcasting and Forecasting, North Shore,
    • Oahu, Hawaii, November 2004.
    • Caldwell, P. and J.Aucan, 2004: AN EMPIRICAL METHOD FOR ESTIMATING SURF
    • HEIGHTS FROM DEEP WATER SIGNIFICANT WAVE HEIGHTS AND PEAK PERIODS IN
    • COASTAL ZONES WITH NARROW SHELVES, STEEP BOTTOM SLOPES, AND HIGH
    • REFRACTION. 8th International Workshop on Wave Hindcasting and Forecasting,
    • North Shore, Oahu, Hawaii, November 2004.
    • Caldwell, P., 2005: Validity of North Shore, Oahu, Hawaiian Islands surf
    • observations. Journal of Coastal Research, 21(1), 2005.
  3. What similar or related data should the user be aware of?

How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?
  2. How accurate are the geographic locations?
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
    none
  5. How consistent are the relationships among the observations, including topology?
    see lineage, process step

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints: None
Use_Constraints: Dataset credit required
  1. Who distributes the data set? (Distributor 1 of 1)
    NOAA/NESDIS/National Oceanographic Data Center
    Attn: Data Access Group, User Services Team
    SSMC-3 Fourth Floor
    Silver Spring, MD
    USA

    301-713-3277 (voice)
    301-713-3302 (FAX)
    services@nodc.noaa.gov
    Hours_of_Service: 8am-5pm, Monday through Friday
  2. What's the catalog number I need to order this data set? Downloadable Data
  3. What legal disclaimers am I supposed to read?
    NOAA makes no warranty regarding these data, expressed or implied, nor does the fact of distribution constitute such a warranty. NOAA, NESDIS, NODC and NCDDC cannot assume liability for any damages caused by any errors or omissions in these data, nor as a result of the failure of these data to function on a particular system.
  4. How can I download or order the data?

Who wrote the metadata?

Dates:
Last modified: 06-Jan-2021
Last Reviewed: 10-Aug-2009
Metadata author:
Mr. Patrick C. Caldwell
NOAA/NESDIS/NODC/NCDDC
Hawaii/US Pacific Liaison
1000 Pope Road, MSB 316
Honolulu, Hawaii
USA

(808)-956-4105 (voice)
(808) 956-2352 (FAX)
caldwell@hawaii.edu
Hours_of_Service: 8 AM to 5 PM weekdays
Contact_Instructions: check services@nodc.noaa.gov if not available
Metadata standard:
FGDC CSDGM (FGDC-STD-001-1998)

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