Offshore Baseline for Texas Generated to Calculate Shoreline Change Rates

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?
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• Who wrote the metadata?

Title:

Offshore Baseline for Texas Generated to Calculate Shoreline Change Rates

Abstract:

Rates of long-term and short-term shoreline change were generated in a GIS with the Digital Shoreline Analysis System (DSAS) version 2.0, an ArcView extension developed by the USGS in cooperation with TPMC Environmental Services. The extension is designed to efficiently lead a user through the major steps of shoreline change analysis. This extension to ArcView contains three main components that define a baseline, generate orthogonal transects at a user-defined separation along the coast, and calculate rates of change (linear regression, endpoint rate, average of rates, average of endpoints, jackknife).

1. How should this data set be cited?

   Morton, Robert, and Miller, Tara, 2004, Offshore Baseline for Texas Generated to Calculate Shoreline Change Rates: 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: -97.373952

   East_Bounding_Coordinate: -93.907110

   North_Bounding_Coordinate: 29.673165

   South_Bounding_Coordinate: 25.957144

3. What does it look like?

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

   Calendar_Date: 2003

   Currentness_Reference: publication date

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 (19)

   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?

   tx_baseline

   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:	10

   TYPE

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

   Value	Definition
   Shoreline	Vector shoreline.
   Baseline	Vector baseline.

   DATE_

   Year constructed. (Source: U.S. Geological Survey)

   Value	Definition
   01/01/2002	Feature constructed in 2002.

   DESCR

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

   Describes additional characteristics of 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

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)

   A baseline was manually constructed seaward of, and parallel to, the trend of shorelines representing four general time periods (1800s, 1920s-1930s, 1970s, and 1998-2002). Using DSAS, transects were generated with a spacing of 50m and transect-shoreline intersection points were saved to a separate layer. Transects were manually eliminated to prevent calculation of rates in areas where less than four shorelines were intersected.

   Long-term rates of shoreline change, in units of m/yr, were calculated at each transect using linear regression applied to all four shoreline positions from the earliest (1800s) to the most recent (derived from lidar). Linear regression was selected because it has been shown to be the most statistically robust quantitative method when a limited number of shorelines are available and it is the most commonly applied statistical technique for expressing shoreline movement and estimating rates of change. Uncertainties for the long-term rates are also reported in units of m/yr and represent a 90% confidence interval for the slope of the regression line. This means with 90% statistical confidence that the true rate of shoreline change falls within the range defined by the reported value plus or minus the error value. The variability around the trend reflects both measurement and sampling errors. Short-term rates of shoreline change, in units of m/yr, were calculated using the endpoint method comparing the 1970s and most recent shoreline positions.

   Person who carried out this activity:
   

   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

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?

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 observations, including topology?

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

Access_Constraints: None

Use_Constraints:

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: 0.026

   • Cost to order the data:

Dates:

Last modified: 06-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>