Vectorized Shoreline of Alabama Derived from 2001 LIDAR Source Data

Frequently-anticipated questions:

• What does this data set describe?
  1. How should this data set be cited?
  2. What geographic area does the data set cover?
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
  5. What is the general form of this data set?
  6. How does the data set represent geographic features?
  7. How does the data set describe geographic features?
• Who produced the data set?
  1. Who are the originators of the data set?
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
• Why was the data set created?
• How was the data set created?
  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
  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?
  5. How consistent are the relationships among the data, including topology?
• How can someone get a copy of the data set?
  1. Are there legal restrictions on access or use of the data?
  2. Who distributes the data?
  3. What's the catalog number I need to order this data set?
  4. What legal disclaimers am I supposed to read?
  5. How can I download or order the data?
• Who wrote the metadata?

Title:

Vectorized Shoreline of Alabama Derived from 2001 LIDAR Source Data

Abstract:

There are critical needs for a nationwide compilation of reliable shoreline data. To meet these needs, the USGS has produced a comprehensive database of digital vector shorelines by compiling shoreline positions from pre-existing historical shoreline databases and by generating historical and modern shoreline data. Shorelines are compiled by state and generally correspond to one of four time periods: 1800s, 1920s-1930s, 1970s, and 1998-2002. Each shoreline may represent a compilation of data from one or more sources for one or more dates provided by one or more agencies. Details regarding source are provided in the 'Data Quality Information' section of this metadata report. Shoreline vectors derived from historic sources (first three time periods) represent the high water line at the time of the survey, whereas modern shorelines (final time period) represent the mean high water line.

1. How should this data set be cited?

   Morton, Robert, Miller, Tara, Sallenger, Abby, and Morgan, Karen, 2004, Vectorized Shoreline of Alabama Derived from 2001 LIDAR Source Data: Open-File Report 2004-1089, U.S. Geological Survey, Coastal and Marine Geology Program, U.S. Geological Survey, Center for Coastal and Watershed Studies, St. Petersburg, FL.

   Online Links:

   • <http://pubs.usgs.gov/of/2004/1089/>

   This is part of the following larger work.

   Morton, Robert, Miller, Tara, and Moore, Laura, 2004, National Assessment of Shoreline Change: Part 1, Historical Shoreline Changes and Associated Coastal Land Loss Along the U.S. Gulf of Mexico: Open-File Report 2004-1043, U.S. Geological Survey, Coastal and Marine Geology Program, U.S. Geological Survey, Center for Coastal and Watershed Studies.

   Online Links:

   • <http://pubs.usgs.gov/of/2004/1043/>
   • <http://coastal.er.usgs.gov/national-assessment/>

2. What geographic area does the data set cover?

   West_Bounding_Coordinate: -88.337457

   East_Bounding_Coordinate: -87.518342

   North_Bounding_Coordinate: 30.279954

   South_Bounding_Coordinate: 30.223485

3. What does it look like?

4. Does the data set describe conditions during a particular time period?

   Calendar_Date: 2001

   Currentness_Reference: ground condition

5. What is the general form of this data set?

   Geospatial_Data_Presentation_Form: vector digital data

6. How does the data set represent geographic features?
   1. How are geographic features stored in the data set?

      This is a Vector data set. It contains the following vector data types (SDTS terminology):

      • String (3617)

   2. What coordinate system is used to represent geographic features?

      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 0.000001. Longitudes are given to the nearest 0.000001. Latitude and longitude values are specified in Decimal degrees.

      The horizontal datum used is North American Datum of 1983.
      The ellipsoid used is Geodetic Reference System 80.
      The semi-major axis of the ellipsoid used is 6378137.000000.
      The flattening of the ellipsoid used is 1/298.257222.
      

7. How does the data set describe geographic features?

   al2001

   FID

   Internal feature number. (Source: ESRI)

   Sequential unique whole numbers that are automatically generated.

   Shape

   Feature geometry. (Source: ESRI)

   Coordinates defining the features.

   ID

   Feature number. (Source: U.S. Geological Survey)

   Range of values
   Minimum:	1
   Maximum:	3445

   TYPE

   Type of feature. (Source: U.S. Geological Survey)

   Value	Definition
   Shoreline	Vector shoreline.
   Baseline	Vector baseline.

   DATE_

   Year of survey. (Source: U.S. Geological Survey)

   Value	Definition
   01/01/2001	Feature surveyed in 2001.

   DESCR

   Detailed description of the feature. (Source: U.S. Geological Survey)

   Describes additional characteristics of the feature.

   SOURCE

   Agency that provided feature or data used to create feature. (Source: U.S. Geological Survey)

   Value	Definition
   USGS	United States Geological Survey

   ACCURACY

   Position accuracy of feature. (Source: U.S. Geological Survey)

   Value	Definition
   0	The accuracy is not given or is not known.

   Range of values
   Units:	meters (m)

1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
   • Robert Morton
   • Tara Miller
   • Abby Sallenger
   • Karen Morgan

2. Who also contributed to the data set?

3. To whom should users address questions about the data?

   U.S. Geological Survey, Center for Coastal and Watershed Studies
   600 4th Street South
   St. Petersburg, FL 33701
   USA
   

   (727) 803-8747 (voice)
   (727) 803-2032 (FAX)
   

   Hours_of_Service: Monday through Friday, 8 a.m. to 5 p.m., Eastern Standard Time

Historical shoreline change is considered to be a crucial element in studying the vulnerability of the national shoreline. These data are used in a shoreline change analysis for the USGS National Assessment Project.

1. From what previous works were the data drawn?

2. How were the data generated, processed, and modified?

   (process 1 of 1)

   The USGS in collaboration with NASA, used the NASA Airborne Topographic Mapper (ATM II and III) mounted on a Twin Otter Aircraft to map coastal beaches. The raw data was georeferenced at elevation points every few square meters. The original data from ATM was collected in WGS 84, ITRF 97, in a geographic (lat/long) coordinate system with irregular spacing. The data was then converted to NAD 83 and NAVD 88. The shoreline generation involved an analysis of shore-normal profiles at 20m intervals alongshore. First, a shore-parallel reference line was digitized as a permanent baseline for any future shoreline generation. Profiles were assessed at 20m intervals perpendicular to the reference line. Each profile consisted of a 4m wide swath of data points. An algorithm determined the shoreline position for each profile based on a regression fit through the foreshore of the profile. The function was evaluated at the mean high water (mhw) level to identify the horizontal position of the shoreline. Results were only accepted if the R-squared value of the regression was significant to the 95% confidence level. The shoreline point solutions were then quality checked in ArcView GIS software against a gray scale elevation grid of the same data. Point solutions were connected to produce a continuous vector shoreline in shapefile format.

   Person who carried out this activity:
   

   Karen L. M. Morgan
   U.S. Geological Survey, Center for Coastal and Watershed Studies
   600 4th Street South
   St. Petersburg, FL 33701
   USA
   

   (727) 803-8747 (voice)
   (727) 803-2032 (FAX)
   kmorgan@usgs.gov
   

   Hours_of_Service: Monday through Friday, 8 a.m. to 5 p.m., Eastern Standard Time

3. What similar or related data should the user be aware of?

1. How well have the observations been checked?

2. How accurate are the geographic locations?

   The maximum positional error for this shoreline, considered independently, is 1.5m. However, if the lidar mean high water shoreline (mhwl) is used for comparison with other high water shorelines (hwl), an additional shoreline proxy offset must be considered. When the offset error is considered, as it pertains to lidar shorelines in the Gulf of Mexico, the total maximum shoreline position error is 18m. Please visit our full report on shoreline change in the Gulf of Mexico (<http://pubs.usgs.gov/of/2004/1043/>), under the heading 'Reliability of the Results', for a complete explanation of the measurement error.

3. How accurate are the heights or depths?

4. Where are the gaps in the data? What is missing?

   This shoreline data adequately represented the shoreline at the time of the survey. Remaining gaps in this data, if applicable, are a consequence of non-existing data or existing data that did not meet quality assurance standards.

5. How consistent are the relationships among the observations, including topology?

   The data set was checked for topological consistency using the Arc/Info command BUILD. No other checks for logical consistency were performed on this data set.

Are there legal restrictions on access or use of the data?

Access_Constraints: None

Use_Constraints:

This data set is not to be used for navigational purposes.

Public domain data from the U.S. government are freely redistributable with proper metadata and source attribution. Please recognize the U.S. Geological Survey (USGS) as the source of this information.

1. Who distributes the data set? (Distributor 1 of 1)

   U.S. Geological Survey, Center for Coastal and Watershed Studies
   600 4th Street South
   St. Petersburg, FL 33701
   USA
   

   (727) 803-8747 (voice)
   (727) 803-2032 (FAX)
   

   Hours_of_Service: Monday through Friday, 8 a.m. to 5 p.m., Eastern Standard Time

2. What's the catalog number I need to order this data set?

   USGS Open-File Report 2004-1089

3. What legal disclaimers am I supposed to read?

   Although these data have been used by the U.S. Geological Survey, U.S. Department of the Interior, these data and information are provided with the understanding that they are not guaranteed to be usable, timely, accurate, or complete. Users are cautioned to consider carefully the provisional nature of these data and information before using them for decisions that concern personal or public safety or the conduct of business that involves substantial monetary or operational consequences. Conclusions drawn from, or actions undertaken on the basis of, such data and information are the sole responsibility of the user.

   Neither the U.S. Government nor any agency thereof, nor any of their employees, contractors, or subcontractors, make any warranty, express or implied, nor assume any legal liability or responsibility for the accuracy, completeness, or usefulness of any data, software, information, apparatus, product, or process disclosed, nor represent that its use would not infringe on privately owned rights.

   Trade, firm, or product names and other references to non-USGS products and services are provided for information only and do not constitute endorsement or warranty, express or implied, by the USGS, USDOI, or U.S. Government, as to their suitability, content, usefulness, functioning, completeness, or accuracy.

4. How can I download or order the data?
   • Availability in digital form:

     Data format:	ESRI Shapefile Seven files comprise the ArcView shapefile: <filename>.dbf, <filename>.shp, <filename>.shx, <filename>.prj, <filename>.avl, <filename>.sbx, <filename>.sbn Size: 0.861

   • Cost to order the data:

Dates:

Last modified: 05-Apr-2004

Metadata author:

U.S. Geological Survey, Center for Coastal and Watershed Studies
c/o Tara Miller
600 4th Street South
St. Petersburg, FL 33701
USA

(727) 803-8747 (voice)
(727) 803-2032 (FAX)
taram@usgs.gov

Hours_of_Service: Monday through Friday, 8 a.m. to 5 p.m., Eastern Standard Time

Metadata standard:

FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)

Metadata extensions used:

• <http://www.esri.com/metadata/esriprof80.html>