There are critical needs for a nationwide compilation of reliable cliff edge data. To meet these needs, the USGS has produced a comprehensive database of digital vector cliff edges by compiling cliff edge positions from pre-existing historical cliff edge databases and by generating historical and modern cliff edge data. Cliff edges are compiled by state and generally correspond to two periods: 1920s-1930s and 1998-2002. Each cliff edge 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. Cliff edge vectors derived from both historic sources (first time period) and modern sources (final time period) represent the cliff edge at the time of the survey.
Historical cliff erosion is considered to be a crucial element in studying the vulnerability of the national coastline. These data are used in a cliff erosion analysis for the USGS National Assessment Project.
ground condition
Public domain data are freely redistributable with proper metadata and source attribution. The U.S. Geological Survey (USGS) must be referenced as the originator of the dataset in any future products or research derived from these data.
Patuxent Wildlife Research Center
University of Rhode Island
317 Woodward Hall, Dept. of Geosciences
The data supplied here are a compilation of information collected from numerous National Ocean Service Coastal Survey Maps (often referred to as t-sheets or tp-sheets). In compiling this product we made no attempt to ascertain the congruency between the charted data, and the real world. Our objective was to simply capture the representative coastline as provided to us via the NOS survey maps. Every effort was made to capture the shoreline on these charts as faithfully as our skills and technology allowed, and there is every indication that we were successful to this end. However, in doing so, we automatically conveyed the character (all aspects, both good and bad) of those data to our digital product. A character which may or may not be in agreement with the real world. Because of this, the user is advised to exercise caution in making any assumptions about the fallibility, or infallibility, of the spatial information supplied here; especially when circumstances warrant a high degree of absolute positional accuracy.
There is significant agreement of linework between adjacent shorelines. Shorelines were checked for accuracy, but no edgematching attempts were made between adjacent shorelines even if slight offsets existed.
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.
The maximum estimated positional error for this cliff edge is 1.4 meters. Please visit our full report on cliff erosion along the Coastline of California (<http://pubs.usgs.gov/of/2007/1133), under the heading "Uncertainties and Errors", for a complete explanation of the measurement error.
NOAA NOS Topographic Sheets (t-sheet or tp-sheet maps)
Cliff edges from one or more sources were sought in an effort to develop a single cliff edge for each time period. Digital cliff edges, if available from another agency, were acquired. If no digital cliff edges were available or if a data set was incomplete, T-sheets were requested from NOAA and received as scanned raster images. T-sheets were geo-registered using ERDAS Imagine geographic imaging software by placing 6-10 well-spaced ground control points at gridline intersections. Some T-sheets may have required additional coordinate transformation information from NOAA to account for datum offsets between historical datums (USSD) and modern datums (NAD27 or NAD83). Datum transformations were applied to GCP coordinates prior to registration. Total RMS error for the rectification process was maintained below 1 pixel, which translates to approximately 4m at a scale of 1:20,000 and 1.5m at a scale of 1:10,000. Geo-registered T-sheets were loaded in ArcView and vector cliff edges were digitized. Quality assessments were performed and cliff edges were edited to remove any overlap between adjacent cliff edges. No edgematching between adjacent cliff edges was attempted. Finally, cliff edges from all sources were merged to produce a single cliff edge for the period. The final cliff edge was coded with 6 attribute fields (ID, Type, Date, Descr, Source, and Accuracy) required for the Digital Shoreline Analysis System (DSAS), which was used to calculate cliff edge erosion rates. The attributes reflect the source of the data and the original survey year.
USGS Patuxent Wildlife Research Center
University of Rhode Island
Coastal Field Station
317 Woodward Hall, Dept. of Geosciences
Data were projected from UTM zone 10 to geographic Tool: ArcGIS > ArcToolbox > Toolboxes > Data Management Tools > Project Command issued: ['GCS_North_American_1983',DATUM['D_North_American_1983',SHPERIOD['GRS_1980',6378137.0,298.25722101]],PRIMEM['Greenwich',0.0],UNIT['Degree',0.0174532925199433]]
384 Woods Hole Road
Internal feature number
ESRI
Feature geometry.
ESRI
Date of vector shoreline position
U.S. Geological Survey
Detailed description of the feature
U.S. Geological Survey
Position accuracy of feature.
U.S. Geological Survey
The accuracy is not given but should be 1.4 meters.
U.S. Geological Survey
Feature number
U.S. Geological Survey
Pacific Science Center
400 Natural Bridges Drive
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.
ESRI Polyline Shapefile. The DBF file contains the attribute data in dBASE format. The PRJ file contains the coordinate system information. The SBN and SBX files contain the spatial index of the geospatial data. The SHP file contains the geospatial data. The SHX file contains the index of the geospatial data. The XML file contains the metadata describing the data set.
USGS Patuxent Wildlife Research Center
University of Rhode Island
Coastal Field Station
317 Woodward Hall, Dept. of Geosciences