Digitized shorelines were checked to ensure they were one continuous line and were checked for dangles (or extra line segments), which were removed, when necessary. Larger estuarine channels were digitized, as needed, to ensure a complete shoreline for later use within shoreline change programs.
Dataset is considered complete for the information presented, as described in the abstract. Users are advised to read the rest of the metadata record carefully for additional details.
Horizontal_Positional_Accuracy:
Horizontal_Positional_Accuracy_Report:
In order to determine the uncertainties associated with individual shorelines, a methodology following Morton and Miller (2005) and Hapke and others, (2006) was used to estimate a positional uncertainty value for each shoreline. Total shoreline positional uncertainty is a function of the errors inherent in the source data (georeferencing Root Mean Square [RMS]) the interpretation of the shoreline feature (WDL positional variability) and those errors generated in the digitization of the vector shoreline (interpolation uncertainty/cell size).
Three terms were identified to describe the shoreline positional uncertainty of the WDL shoreline. The first is the total image Root Sum Squared (RSS) of the georeferenced aerial imagery. This measure takes into account the accuracy of the georeferenced image, as well as the uncertainty of the base to wich the imagery was georeferenced to. The second term is based on the natural variability of the shoreline proxy. The positional variability of an interpolated WDL shoreline is influenced primarily by tides, winds, waves and beach slope. Similarly, other water level based proxies (HWL - high water line, LHTS- last high tide swash) have positional variability, which is weather and tide dependent. Drawing on methods presented in Pajak and Leathermann (2002), a conservative estimate of WDL variability (given tide range and average beach slope) of 4.5 m is calculated for Dauphin Island. The third and final term is based on the cell size of the georeferenced image, which relates to the scale of the image and accounts for limitations of shoreline interpretation from the raster data.
These terms were summed in quadrature and the resulting shoreline positional uncertainty was applied to each shoreline date in the "UNCERT" field of the attribute table. This value is used to determine the uncertainty of shoreline change rates when used with the Digital Shoreline Analysis System (DSAS; Thieler and others, 2009).
Quantitative_Horizontal_Positional_Accuracy_Assessment:
Horizontal_Positional_Accuracy_Value: 9.7
Horizontal_Positional_Accuracy_Explanation:
The horizontal positional accuracy value is presented as an average of the 10 aerial shoreline uncertainty values. Each shoreline was assigned a unique uncertainty based on: 1) RSS of the georeferenced aerial imagery 2) estimate of WDL variability 3) cell size limitation.
The following are the estimated uncertainties for each date. Values are in meters.
19401027 (10.5)
19520429 (13.0)
19601102 (9.4)
19741204 (9.2)
19850601 (10.9)
19890918 (11.8)
19920201 (8.4)
19972011 (8.4)
20060623 (7.6)
20151112 (7.5)
Average = 9.7 m
Source_Information:
Source_Citation:
Citation_Information:
Originator: U.S. Geological Survey (USGS)
Publication_Date: 19740429
Title: Aerial Single Frame Photos - Dauphin Island 1940
Geospatial_Data_Presentation_Form: Photos
Publication_Information:
Publication_Place: Sioux Falls, South Dakota
Publisher:
U.S. Geological Survey (USGS) Earth Resources Observation and Science (EROS) Center
Other_Citation_Details:
The Aerial Photography Single Frame Records collection is a large and diverse group of imagery acquired by Federal organizations from 1937 to the present. Over 6.4 million frames of photographic images are available for download as medium and high resolution digital products. The high resolution data provide access to photogrammetric quality scans of aerial photographs with sufficient resolution to reveal landscape detail and to facilitate the interpretability of landscape features. Coverage is predominantly over the United States and includes portions of Central America and Puerto Rico. Individual photographs vary in scale, size, film type, quality, and coverage.
Online_Linkage: https://lta.cr.usgs.gov/Single_Frame_Records
Source_Scale_Denominator: 48000
Type_of_Source_Media: Digital and/or Hardcopy Resources.
Source_Time_Period_of_Content:
Time_Period_Information:
Single_Date/Time:
Calendar_Date: 19401027
Source_Currentness_Reference: Ground Condition
Source_Citation_Abbreviation: Dauphin_1940
Source_Contribution:
Imagery provided by EROS via direct download. Imagery was georectified and then used to delineate and digitize shoreline positions.
Source_Information:
Source_Citation:
Citation_Information:
Originator: U.S. Geological Survey (USGS)
Publication_Date: 19750707
Title: Aerial Single Frame Photos - Dauphin Island 1952
Geospatial_Data_Presentation_Form: Photos
Publication_Information:
Publication_Place: Sioux Falls, South Dakota
Publisher:
U.S. Geological Survey (USGS) Earth Resources Observation and Science (EROS) Center
Other_Citation_Details:
The Aerial Photography Single Frame Records collection is a large and diverse group of imagery acquired by Federal organizations from 1937 to the present. Over 6.4 million frames of photographic images are available for download as medium and high resolution digital products. The high resolution data provide access to photogrammetric quality scans of aerial photographs with sufficient resolution to reveal landscape detail and to facilitate the interpretability of landscape features. Coverage is predominantly over the United States and includes portions of Central America and Puerto Rico. Individual photographs vary in scale, size, film type, quality, and coverage.
Online_Linkage: https://lta.cr.usgs.gov/Single_Frame_Records
Source_Scale_Denominator: 69000
Type_of_Source_Media: Digital and/or Hardcopy Resources
Source_Time_Period_of_Content:
Time_Period_Information:
Single_Date/Time:
Calendar_Date: 19520430
Source_Currentness_Reference: Ground Condition
Source_Citation_Abbreviation: Dauphin_1952
Source_Contribution:
Imagery provided by EROS via direct download. Imagery was georectified and then used to delineate and digitize shoreline positions.
Source_Information:
Source_Citation:
Citation_Information:
Originator: United States Department of Agriculture - Farm Service Agency
Publication_Date: Unknown
Title: Aerial Imagery Mobile County, Alabama, 1960
Publication_Information:
Publication_Place: Salt Lake City, Utah
Publisher: United States Department of Agriculture - Farm Service Agency
Other_Citation_Details:
The Aerial Photography Field Office (APFO) has a vast amount of imagery of the United States and its territories from 1955 to the present.
Online_Linkage:
Source_Scale_Denominator: 20000
Type_of_Source_Media: Digital and/or Hardcopy Resources
Source_Time_Period_of_Content:
Time_Period_Information:
Single_Date/Time:
Calendar_Date: 19601102
Source_Currentness_Reference: Ground Condition
Source_Citation_Abbreviation: Dauphin_1960
Source_Contribution:
Imagery provided by USDA-FSA as high-resolution scans(.tif) on hard disk via post. Imagery was georectified and then used to delineate and digitize shoreline positions.
Source_Information:
Source_Citation:
Citation_Information:
Originator:
Geological Survey of Alabama - Acquired from University of Alabama's Cartographic Research Laboratory.
Publication_Date: Unknown
Title: Aerial Photography Mobile County, Alabama, 1974
Publication_Information:
Publication_Place: Tuscaloosa, Alabama
Publisher: Cartographic Research Laboratory
Other_Citation_Details:
Alabama Maps is an ongoing project of the Cartographic Research Laboratory, which operates under the auspices of the College of Arts and Sciences at the University of Alabama. The Cartographic Research Laboratory , established in 1982, is a self-supporting, nonprofit facility, receiving funding through the sale of our publications and projects from clientele. The Aerial Photography Index contains a digitized selection of historic aerial photography found at the Geological Survey of Alabama and the University of Alabama Map Library. The photos found in this index are but a small part of the total collection of nearly 150,000 photographs housed in these facilities.
Online_Linkage: http://alabamamaps.ua.edu
Source_Scale_Denominator: 40000
Type_of_Source_Media: Digital and/or Hardcopy Resources
Source_Time_Period_of_Content:
Time_Period_Information:
Single_Date/Time:
Calendar_Date: 19741204
Source_Currentness_Reference: Ground Condition
Source_Citation_Abbreviation: Dauphin_1974
Source_Contribution:
Imagery provided by the Cartographic Research Laboratory as high-resolution scans (.tif) via direct download. Imagery was georectified and then used to delineate and digitize shoreline positions.
Source_Information:
Source_Citation:
Citation_Information:
Originator: U.S. Geological Survey (USGS)
Publication_Date: 19980804
Title:
National High Altitude Photography, Mobile County, Alabama, 1985
Publication_Information:
Publication_Place: Sioux Falls, South Dakota
Publisher:
U.S. Geological Survey (USGS) ) Earth Resources Observation and Science (EROS) Center
Other_Citation_Details:
The National High Altitude Photography (NHAP) program, which was operated from 1980-1989, was coordinated by the U.S. Geological Survey as an interagency project to eliminate duplicate photography in various government programs. The aim of the program was to cover the 48 conterminous states over a 5-year span. In the NHAP program, black-and-white and color-infrared aerial photographs were obtained on 9-inch film from an altitude of 40,000 feet above mean terrain elevation and are centered over USGS 7.5-minute quadrangles. The color-infrared photographs are at a scale of 1:58,000 (1 inch equals about .9 miles), and the black-and-white photographs are at a scale of 1:80,000 (1 inch equals about 1.26 miles). All NHAP flights were flown in a North to South direction. These photographs are offered as digital images.
Online_Linkage: https://lta.cr.usgs.gov/NHAP
Source_Scale_Denominator: 58000
Type_of_Source_Media: Digital and/or Hardcopy Resources
Source_Time_Period_of_Content:
Time_Period_Information:
Single_Date/Time:
Calendar_Date: 19850325
Source_Currentness_Reference: Ground Condition
Source_Citation_Abbreviation: Dauphin_1985
Source_Contribution:
Imagery provided by EROS via direct download. Imagery was georectified and then used to delineate and digitize shoreline positions.
Source_Information:
Source_Citation:
Citation_Information:
Originator: U.S. Geological Survey (USGS)
Publication_Date: 19900125
Title: Aerial Single Frame Photos - Dauphin Island 1989
Geospatial_Data_Presentation_Form: Photo
Publication_Information:
Publication_Place: Sioux Falls, South Dakota
Publisher:
U.S. Geological Survey (USGS) Earth Resources Observation and Science (EROS) Center
Other_Citation_Details:
The Aerial Photography Single Frame Records collection is a large and diverse group of imagery acquired by Federal organizations from 1937 to the present. Over 6.4 million frames of photographic images are available for download as medium and high resolution digital products. The high resolution data provide access to photogrammetric quality scans of aerial photographs with sufficient resolution to reveal landscape detail and to facilitate the interpretability of landscape features. Coverage is predominantly over the United States and includes portions of Central America and Puerto Rico. Individual photographs vary in scale, size, film type, quality, and coverage.
Online_Linkage: https://lta.cr.usgs.gov/Single_Frame_Records
Source_Scale_Denominator: 65000
Type_of_Source_Media: Digital and/or Hardcopy Resources.
Source_Time_Period_of_Content:
Time_Period_Information:
Single_Date/Time:
Calendar_Date: 19890918
Source_Currentness_Reference: Ground Condition
Source_Citation_Abbreviation: Dauphin_1989
Source_Contribution:
Imagery provided by EROS via direct download. Imagery was georectified and then used to delineate and digitize shoreline positions.
Source_Information:
Source_Citation:
Citation_Information:
Originator:
U.S. Geological Survey (USGS) Earth Resources Observation and Science (EROS) Center
Publication_Date: 19970514
Title: Digital Orthophoto Quadrangle, Dauphin Island, Alabama, 1992
Geospatial_Data_Presentation_Form: Remote-Sensing Image
Publication_Information:
Publication_Place: Menlo Park, CA USA
Publisher: U.S. Geological Survey
Other_Citation_Details:
Orthophotos combine the image characteristics of a photograph with the geometric qualities of a map. The primary digital orthophotoquadrangle (DOQ) is a 1-meter ground resolution, quarter-quadrangle (3.75 minutes of latitude by 3.75 minutes of longitude) image cast on the Universal Transverse Mercator projection (UTM) on the North American Datum of 1983 (NAD83). The geographic extent of the DOQ is equivalent to a quarter-quadrangle plus the overage ranges from a minimum of 50 meters to a maximum of 300 meters beyond the extremes of the primary and secondary corner points. The overage is included to facilitate tonal matching for mosaicking and for the placement of the NAD83 and secondary datum corner ticks. The normal orientation of data is by lines (rows) and samples (columns). Each line contains a series of pixels ordered from west to east with the order of the lines from north to south. The radiometric image brightness values are stored as 256 gray levels, ranging from 0 to 255. The standard, uncompressed gray scale DOQ format contains an ASCII header followed by a series of 8-bit image data lines. The keyword-based, ASCII header may vary in the number of data entries. The header is affixed to the beginning of the image and is composed of strings of 80 characters with an asterisk (*) as character 79 and an invisible newline character as character 80. Each keyword string contains information for either identification, display, or registration of the image. Additional strings of blanks are added to the header so that the length of a header line equals the number of bytes in a line of image data. The header line will be equal in length to the length of an image line. If the sum of the byte count of the header is less than the sample count of one DOQ image line, then the remainder of the header is padded with the requisite number of 80-character blank entries, each terminated with an asterisk and newline character.
Online_Linkage: https://lta.cr.usgs.gov/DOQs
Source_Scale_Denominator: 40000
Type_of_Source_Media: Digital and/or Hardcopy Resources
Source_Time_Period_of_Content:
Time_Period_Information:
Single_Date/Time:
Calendar_Date: 19920201
Source_Currentness_Reference: Ground Condition
Source_Citation_Abbreviation: Dauphin_1992
Source_Contribution:
Imagery provided by EROS via direct download. Imagery was used to delineate and digitize shoreline positions.
Source_Information:
Source_Citation:
Citation_Information:
Originator:
U.S. Geological Survey (USGS) Earth Resources Observation and Science (EROS) Center
Publication_Date: 19970211
Title:
The National Aerial Photography Program Imagery, Mobile County, Alabama, 1997
Geospatial_Data_Presentation_Form: Photograph and/or High Resolution Scanned Image
Publication_Information:
Publication_Place: Sioux Falls, South Dakota
Publisher:
U.S. Geological Survey (USGS) Earth Resources Observation and Science (EROS) Center
Other_Citation_Details:
The National Aerial Photography Program (NAPP) was coordinated by the USGS as an interagency project to acquire cloud-free aerial photographs at an altitude of 20,000 feet above mean terrain elevation. The photographs were taken with a 6-inch focal length lens and are at a scale of 1:40,000. Coverage over the conterminous United States includes both black-and-white (BW) and color infrared (CIR) aerial photographs. Film type and extent of coverage were determined by available funds and operational requirements. The NAPP program, which was operational from 1987 to 2007, consists of more than 1.3 million images. Photographs were acquired on 9-inch film and were centered over quarters of USGS 7.5-minute quadrangles.Photographs are available as medium resolution digital images in Tagged Image File Format (TIFF). Medium resolution digital products were created with a digital single-lens reflex camera at a resolution of 63 microns, or 400 dots per inch (dpi).
Online_Linkage: https://lta.cr.usgs.gov/NAPP
Source_Scale_Denominator: 40000
Type_of_Source_Media: Digital and/or Hardcopy Resources.
Source_Time_Period_of_Content:
Time_Period_Information:
Single_Date/Time:
Calendar_Date: 19970211
Source_Currentness_Reference: Ground Condition
Source_Citation_Abbreviation: Dauphin_1997
Source_Contribution:
Imagery provided by EROS via direct download. Imagery was georectified and then used to delineate and digitize shoreline positions.
Source_Information:
Source_Citation:
Citation_Information:
Originator: USDA-FSA-APFO
Publication_Date: 20061206
Title:
USDA-FSA-APFO Digital Ortho Mosaic, Mobile County, Alabama, 2006
Geospatial_Data_Presentation_Form: Orthorectified Digital Aerial Photography
Publication_Information:
Publication_Place: Salt Lake City, Utah
Publisher: USDA_FSA_APFO Aerial Photography Field Office
Other_Citation_Details:
This data set contains imagery from the National Agriculture Imagery Program (NAIP). NAIP acquires digital ortho imagery during the agricultural growing seasons in the continental U.S.. A primary goal of the NAIP program is to enable availability of ortho imagery withone year of acquisition. NAIP provides four main products: 1-meter ground sample distance (GSD) ortho imagery rectified to a horizontal accuracy of within +/- 5meters of reference digital ortho quarter quads (DOQQ's) from the National Digital Ortho Program (NDOP); 2-meter GSD ortho imagery rectified to within +/- 10 meters of reference DOQQs; 1-meter GSD ortho imagery rectified to within +/- 6 meters to true ground; and, 2 meter GSD ortho imagery rectified to within +/- 10 meters to true ground. The tiling format of NAIP imagery is based on a 3.75' x 3.75' quarter quadrangle with a 300-meter buffer on all four sides. NAIP quarter quads are formatted to the UTM coordinate system using NAD83. NAIP imagery may contain as much as 10% cloud cover per tile. Dauphin_2006 was generated by compressing NAIP quarter quadrangle tiles that cover a county. MrSID compression, with mosaic option, was used. Target values for the compression ratio are (15:1) and maximum number of compression levels are used.
Online_Linkage: https://gdg.sc.egov.usda.gov
Source_Scale_Denominator: 40000
Type_of_Source_Media: Digital and/or Hardcopy Resources.
Source_Time_Period_of_Content:
Time_Period_Information:
Single_Date/Time:
Calendar_Date: 20060630
Source_Currentness_Reference: Ground Condition
Source_Citation_Abbreviation: Dauphin_2006
Source_Contribution:
Imagery provided by USDA Geospatial Data Gateway via direct download. Imagery was used to delineate and digitize shoreline positions.
Source_Information:
Source_Citation:
Citation_Information:
Originator: USDA-FSA-APFO
Publication_Date: 20151112
Title:
USDA-FSA-APFO Digital Ortho Mosaic, Mobile County, Alabama, 2015
Geospatial_Data_Presentation_Form: Orthorectified Digital Aerial Photography
Publication_Information:
Publication_Place: Salt Lake City, Utah
Publisher: USDA_FSA_APFO Aerial Photography Field Office
Online_Linkage: https://gdg.sc.egov.usda.gov
Source_Scale_Denominator: 12000
Type_of_Source_Media: Digital and/or Hardcopy Resources.
Source_Time_Period_of_Content:
Time_Period_Information:
Single_Date/Time:
Calendar_Date: 20151112
Source_Currentness_Reference: Ground Condition
Source_Citation_Abbreviation: Dauphin_2015
Source_Contribution:
Imagery provided by USDA Geospatial Data Gateway via direct download. Imagery was used to delineate and digitize shoreline positions.
Process_Step:
Process_Description:
Imagery was acquired from multiple agencies as direct download or as hard copy. The images are projected to Universal Transverse Mercator (UTM), Zone 16, North American Datum (NAD) 1983, meters (m) coordinates. If the imagery was not georeferenced when obtained, the corner coordinates and multiple control points were used to georeference the image using the ArcMap 10.3.1 "Georeference" toolbar. Using the ArcMap editor toolbar, shorelines were digitized based on aerial imagery.
Shorelines were digitized based on a visual assessment of the WDL along sandy beaches and the approximation of mean high water where vegetation indicated. Shorelines were digitized at a scale of 1:1000. Once digitization was complete, shoreline segments were given attributes “DATE_” (text string 10 characters) and "UNCERT" (double), and "NOTES_". "DATE_" is determined from the aerial imagery collection date in MM/DD/YYYY format, "UNCERT" remains blank until completion of shoreline positional uncertainty (to follow). "NOTES_" contain information about each shoreline segment, according to 1) location along the island (for example, Dauphin Island, Little Dauphin Island, Pelican Island) and shoreline type (open-ocean, back-barrier, marsh shoreline).
Once all data was populated with dates, the shoreline years were combined into one shapefile.
Source_Used_Citation_Abbreviation: Dauphin_1940
Source_Used_Citation_Abbreviation: Dauphin_1952
Source_Used_Citation_Abbreviation: Dauphin_1960
Source_Used_Citation_Abbreviation: Dauphin_1974
Source_Used_Citation_Abbreviation: Dauphin_1985
Source_Used_Citation_Abbreviation: Dauphin_1989
Source_Used_Citation_Abbreviation: Dauphin_1992
Source_Used_Citation_Abbreviation: Dauphin_1997
Source_Used_Citation_Abbreviation: Dauphin_2006
Source_Used_Citation_Abbreviation: Dauphin_2015
Process_Date: 20160516
Source_Produced_Citation_Abbreviation: Aerial_WDL_Shorelines_1940_2015
Process_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Paul R Nelson
Contact_Organization: U.S. Geological Survey
Contact_Address:
Address_Type: mailing and physical
Address: 600 4th Street South
City: St. Petersburg
State_or_Province: Florida
Postal_Code: 33701
Country: US
Contact_Voice_Telephone: (727)-502-8127
Contact_Electronic_Mail_Address: prnelson@usgs.gov
Process_Step:
Process_Description:
In order to determine the uncertainties associated with individual shorelines, a methodology following Morton and Miller (2005) and Hapke and others, (2006) was used to estimate a positional uncertainty value for each shoreline. Total shoreline positional uncertainty is a function of the errors inherent in the source data (georeferencing RMS) the interpretation of the shoreline feature (WDL positional variability) and those errors generated in the digitization of the vector shoreline (interpolation uncertainty/cell size).
Three terms were identified to describe the shoreline positional uncertainty of the WDL shoreline. The first is the total image RSS of the georeferenced aerial imagery. This measure takes into account the accuracy of the georeferenced image, as well as the uncertainty of the base to which the imagery was georeferenced to. The second term is based on the natural variability of the shoreline proxy. The positional variability of an interpolated WDL shoreline is influenced primarily by tides, winds, waves and beach slope. Similarly, other water level based proxies (HWL - high water line, LHTS- last high tide swash) have positional variability which is weather and tide dependent. Drawing on methods presented in Pajak and Leathermann (2002), a conservative estimate of WDL variability (given tide range and average beach slope) of 4.5 m is calculated for Dauphin Island. The third and final term is based on the cell size of the georeferenced image, which relates to the scale of the image and accounts for limitations of shoreline interpretation from the raster data.
These terms were summed in quadrature and the resulting shoreline positional uncertainty was applied to each shoreline date in the "UNCERT" field of the attribute table. This value is used to determine the uncertainty of shoreline change rates when used with the Digital Shoreline Analysis System (DSAS; Thieler and others, 2009).
Source_Used_Citation_Abbreviation: Aerial_WDL_Shorelines_1940_2015
Process_Date: 20170301
Source_Produced_Citation_Abbreviation: Aerial_Shorelines_1940_2015.shp
Process_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Rachel Henderson
Contact_Organization: U.S. Geological Survey
Contact_Address:
Address_Type: mailing and physical
Address: 600 4th Street South
City: St. Petersburg
State_or_Province: Florida
Postal_Code: 33701
Country: US
Contact_Voice_Telephone: (727)-502-8000
Contact_Electronic_Mail_Address: rehenderson@usgs.gov
Process_Step:
Process_Description:
Added keywords section with USGS persistent identifier as theme keyword.
Process_Date: 20201013
Process_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: U.S. Geological Survey
Contact_Person: VeeAnn A. Cross
Contact_Position: Marine Geologist
Contact_Address:
Address_Type: Mailing and Physical
Address: 384 Woods Hole Road
City: Woods Hole
State_or_Province: MA
Postal_Code: 02543-1598
Contact_Voice_Telephone: 508-548-8700 x2251
Contact_Facsimile_Telephone: 508-457-2310
Contact_Electronic_Mail_Address: vatnipp@usgs.gov
