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  • GIS Layer Field Names and Standard Fields

    Our GIS Library data layers are stored in several formats, including ESRI Coverages, ESRI Shapefiles and ESRI Geodatabases. Each of these formats may have restrictions on attribute field names or define fields unique to the format.

    ESRI Coverage Field Names

    Coverage field names are from ESRI Coverage format data. Coverage standard items (aka stump items or fields) from feature class tables (AAT, PAT, NAT, BND, SEC, TIC, etc.) are not shown. However, if these layers were converted from coverage format to Shapefile format at some point, these items may appear as converted to Shapefile field names.

    Stump items for polygon or point feature types, PAT (where "cover" is the coverage name):

    • AREA
    • PERIMETER
    • cover# (cover_ when converted to a Shapefile)
    • cover-ID (cover_ID or cover_I when converted to a Shapefile)

    Stump items for line feature types, AAT (where "cover" is the coverage name):

    • FNODE# (FNODE_ when converted to a Shapefile)
    • TNODE# (TNODE_ when converted to a Shapefile)
    • LPOLY# (LPOLY_ when converted to a Shapefile)
    • RPOLY# (RPOLY_ when converted to a Shapefile)
    • LENGTH
    • cover# (cover_ when converted to a Shapefile)
    • cover-ID (cover_ID or cover_I when converted to a Shapefile)

    There are many other, different stump items for less common feature classes. These include ARC#, XMIN, YMIN, XMAX, YMAX, POLY#, RINGS_NOK, RINGS_OK, SUBCLASS, SUBCLASS#, ROUTELINK#, ARCLINK#, F-MEAS, T-MEAS, F-POS, T-POS, IDTIC, XTIC, YTIC and their equivalents as converted to Shapefiles. See "item definitions" in ArcInfo Workstation help for more information on these fields, their meaning and use.

    ESRI Shapefile Field Names

    Shapefile field names are derived from coverage field names, not actual Shapefiles. Field names may differ in ESRI Shapefile format.
    • All occurences of "#", "-", and "." in coverage field names are replaced with underscore.
    • Coverage field names longer than 10 characters are truncated to 10 characters during conversion to Shapefile format.
    Shapefile field names that differ from their corresponding coverage names are marked with an asterisk.

    Shapefile format does not define any standard or "stump" fields.

    ESRI Geodatabase Field Names

    The Geodatabase format defines a few standard fields included in all layers. These fields and their handling depends on the particular Geodatabase storage mechanism:

    ArcSDE Compressed Binary and File-based Geodatabase: We use ArcSDE compressed Binary to store our Enterprise Geodatabase. ArcSDE compressed Binary is used in a database such as Microsoft SQL Server. ArcSDE Compressed Binary Geodatabases and File-based Geodatabases (as opposed to personal geodatabases) store and calculate certain standard fields on the fly as part of their native processing. Those fields are:

    • All Feature Classes
      • OBJECTID
    • Polygon Feature Classes
      • Shape.Area – (Exported as Shape_Area)
      • Shape.Length – (Exported as Shape_Length to a Personal Geodatabase and as Shape_Len to a Shapefile.)
    • Line Feature Classes
      • Shape.Length – (Exported as Shape_Length to a Personal Geodatabase and as Shape_Len to a Shapefile.)

    Personal Geodatabase: A Personal Geodatabase is an Access MDB file. ArcMap calculates several fields on the fly:

    • All Feature Classes
      • OBJECTID
    • Polygon Feature Classes
      • Shape_Area
      • Shape_Length (Exported as SHAPE_LENG to a Shapefile.)
    • Line Feature Classes
      • Shape_Length (Exported as SHAPE_LENG to a Shapefile.)

    Oracle Spatial SDO Geometry: We do not use Oracle Spatial to store our Enterprise Geodatabase at this time. Certain fields are defined and displayed in ArcGIS, but are not stored physically in the database.

    • All Feature Classes
      • SE_ANNO_CAD_DATA – This field is added by SDE to Oracle Spatial tables to store data that cannot be stored in the geometry column. It is not exported. Data stored in this field includes annotation features, parametric curve features, and CAD data.
    • Polygon Feature Classes - These fields are not used by Oracle Spatial. They are visible in ArcMap but the values are always 0 and the fields don't actually exist in the table.
      • Shape.Area (Re-calculated at export time. Exported as Shape_Area.)
      • Shape.Length (Re-calculated at export time. Exported as Shape_Length to a Personal Geodatabase and as Shape_Len to a Shapefile.)
    • Line Feature Classes – This field is not used by Oracle Spatial. It is visible in ArcMap but the value is always 0 and the field doesn’t actually exist in the table.
      • Shape.Length (Re-calculated at export time. Exported as Shape_Length to a Personal Geodatabase and as Shape_Len to a Shapefile.)
    • Feature Classes that store annotation
      • SE_ANNO_TEXT – This field is added to store the text of the annotation. It is not exported
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