This data set contains OCS block outlines in ArcGIS shapefile format for the BOEM Alaska Region. OCS blocks are used to define small geographic areas within an Official Protraction Diagram (OPD) for leasing and administrative purposes. These blocks have been clipped along the Submerged Lands Act (SLA) boundary and along the Continental Shelf Boundaries. Additional details are available from: http://www.boem.gov/BOEM-Newsroom/Library/Publications/1999/99-0006-pdf.aspx Because GIS projection and topology functions can change or generalize coordinates, and because shapefiles can not represent true arcs, these GIS files are considered to be approximate and are NOT an OFFICIAL record for the exact block coordinates or areas. The Official Protraction Diagrams (OPDs) and Supplemental Official Block Diagrams (SOBDs) serve as the legal definition for BOEM offshore boundary coordinates and area descriptions.
These block polygons and other cadastre information the BOEM produces are generated in accordance with 30 Code of Federal Regulations (CFR) 256.8 to support Federal land ownership and mineral resource management.
The BOEM is making its existing cadastre data available at http://www.boem.gov/Oil-and-Gas-Energy-Program/Mapping-and-Data/Index.aspx. These data include Official Protraction Diagrams (OPDs), and Supplemental Official OCS Block Diagrams (SOBDs) in pdf format, and digital spatial data in ArcGIS shapefile format.
publication date
The data was developed within the U.S. Government; no proprietary rights may be attached to them nor may they be sold to the U.S. Government as part of any procurement of digital data products or services.
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The file is believed to be free of topologic errors.
The entire Alaska Region consists of 285 NAD 83 Official Protraction Diagrams (OPDs), yet not all have been published in the federal register. A total of 69 OPDs remain to be published. The browse graphic distinguishes the difference between the published OPDs and the unpublished OPDs. Another way to tell if an OPD is published or unpublished is by looking at the PROT_APRV_ field in the attribute table. If the PROT_APRV_ field is blank, then the OPD is considered unpublished. The completion date of the entire Alaska Region OPDs is unknown at this time.
Coordinates values have been computed to .00000001 of a degree, but this shapefile is considered approximate. Where differences occur between the shapefile and the OPD and SOBD diagrams, the diagrams take precedence.
Coordinates and attributes for block polygons.
In house programs were used to protract offshore blocks OPD by OPD, on a UTM grid for the offshore areas. Additional boundaries, including the Submerged Lands Act boundary, the Continental Shelf boundary, and others were also computed and intersected with the OPD blocks. The resulting points were then stored in the TIMS database. Other in-house programs were used to create an ArcInfo Coverage from the data stored in the TIMS database. That coverage was converted into a shapefile using ArcGIS, and any portions of blocks landward of the SLA boundary of seaward of the CSB boundary were removed. The shapefile was further "dissolved" to remove any other internal boundary line, leaving only the block outlines.
381 Elden St.
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Dataset copied.
Internal feature number.
ESRI
Feature geometry.
ESRI
Protraction Number is the identifier of an Official Protraction Diagram
Bureau of Ocean Energy Management
Protraction Approval Date is the day, month and year the Official Protraction Diagram is signed by the Federal Government and approved for distribution.
Bureau of Ocean Energy Management
Block Number is the identifier of a subdivision of an Official Protraction Diagram
Bureau of Ocean Energy Management
Block Federal Approval Date is usually the same as the Protraction Approval Date, but occasionally an individual block can be revised and have a newer date than the rest of the Protraction.
Bureau of Ocean Energy Management
Region Code is the identifier used to identify the BOEM Outer Continental Shelf (OCS) Region.
Bureau of Ocean Energy Management
Planning Area Code is the code used to designate an OCS planning area.
Bureau of Ocean Energy Management
Perimeter is computed by ESRI in coverage units (degrees) - NOT the official BOEM TIMS measurement.
ESRI
Area is computed by ESRI in coverage units (square degrees) - NOT the official BOEM TIMS acreage.
ESRI
Attributes to describe the blocks and sub blocks, but there are no attributes in this table that indicate whether a block has been leased or not
Bureau of Ocean Energy Management
381 Elden St.
Mail Stop HM3120
As is. No responsibility is assumed for the correctness of this data.
381 Elden St
Mail Stop HM3120