Ordnance survey: Boundary-Line (NTFB)

Long name NTF Boundary Line
Short name NTFB
File extension(s) .ntf
Boundary-Line is a structured vector data set. Each polygon contains a seed with its attributes; the links that represent its boundaries carry explicit pointers to the seed. Three vector layers may be used to display the NTF file's four data sets:
  1. line
  2. polygon
  3. complex polygon
  4. collect

Boundary-Line(NTF v2.0 level 3) are supported by the GDB library for import and view.

Structure of features

The structure of each different feature is as follows:
  1. Line Feature

    • a Geometry Record [GEOMETRY1] 21
    • Geometry Continuation Records
    • an associated Attribute Record [ATTREC] 14
  2. Polygon Feature

    • a Polygon Record [POLYREC] 31
    • a Geometry Record [GEOMETRY1] 21
    • a Chain Record [CHAINREC]24 and and maybe one or more
    • continuation Records[CONTREC] 00 to extend the Chain Record
    • an associated Attribute Record [ATTREC] 14
  3. Complex Polygon Feature

    • a Complex Polygon Record [CPOLYREC] 33 and and maybe one or more
    • continuation Records[CONTREC] 00 to extend the CPoly Record
    • an associated Attribute Record [ATTREC] 14, maybe one or more
    • continuation Records[CONTREC] 00 to extend the Attribute Record
  4. Collect Feature

    • a Collect Record [COLLECTREC] 34
    • an associated Attribute Record [ATTREC] 14,maybe one or more
    • continuation Records[CONTREC] 00 to extend the Attribute Record

Coordinate referencing system

Coordinate values and the number of coordinate pairs in a feature are transferred in the Geometry Record [GEOMETRY1]. All coordinates are expressed as strings of six numeric characters for the Eastings and Northings. All coordinates are measured from the local origin, which is the south-west corner of the 25 km by 25 km tile.To convert coordinate data to full National Grid coordinates, add the coordinates of the feature to those of the SW corner of the 25 km by 25 km tile. The SW corner coordinates are contained within the {X_ORIG} and {Y_ORIG} fields of the Section Header Record [SECHREC].

See UK National Transfer Format (NTF) for information on georeferencing.

Bounding-Line 2000 the differences:

.. Removal of feature coding
.. Removal of tile based supply. The data will be supplied by named files
   instead of the 25km*25km numbered tiles.
.. Removal of polygon seeds
.. Addition of area codes at the administration level
.. Addition of explicit administration and/or voting area relationships
.. Removal of explicit foreshore areas

Others change:

.. Each polygon carries ID, HA attributes
.. Each link(line) carries LK-ID, FC attributes
.. Each collection carries: AI, NM, OP, AC, NB, NA, TY attributes
.. All coordinates are expressed as string of eight numeric characters
   for the eastings and eight numeric characters for the northing(before, 
   this number is six), where appropriate, leading zeros are present to
   complete the eight characters.

For more detail, see Bounding-Line 2000 User Guide

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