Strategi vector file (NTF)

Long name NTF Strategi
Short name NTFS
File extension(s) .ntf

Strategi Data(NTF v2.0 level 3) are supported by the GDB library for import and view. It is supplied by national cover, selected layer, regional cover, or 50km by 50km tiles.

Strategi is defined as a limited "link and node" structure. It contains points, lines and nodes. Nodes have pointers to lines (links) that join at the node but there is no explicit topology within the data. Similarly, there are lines (links) that enclose an area containing a point (seed), and again there is no explicit topology between the lines (links) and point(seed). Some points (seeds) are not contained within areas enclosed by lines (links). Four vector layers may be used to display its three data set:
  1. point
  2. line
  3. node
  4. text

Structure of features

The structure of each different feature is as follows:
  1. Point Feature:
    • a Point Record [POINTREC] 15
    • a Geometry Record [GEOMETRY1] 21
    • an associated Attribute Record [ATTREC] 14, which contains a measurement for variable sized symbols.
  2. Line Feature:
    • a Line Record [LINEREC] 23
    • a Geometry Record [GEOMETRY1] 21,and maybe one or more continuation Records[CONTREC] 00 to extend the Geometry Record.
    • an associated Attribute Record [ATTREC] 14
  3. Node Feature:
    • a Node Record [NODEREC] 16,and maybe one or more continuation Records[NODECONT] 00 to extend the Node Record
    • a Geometry Record [GEOMETRY1] 21
    • a Point Record [POINTREC] 15
    • an associated Attribute Record [ATTREC] 14
  4. Text Feature:
    • a Text Record [TEXTREC] 43
    • a Text Position Record [TEXTPOS] 44
    • a Text Position Record [TEXTREP] 45
    • a Geometry Record [GEOMETRY1] 21
    • an associated Attribute Record [ATTREC] 14

Coordinate referencing system

Coordinate values and the number of coordinate pairs in a feature are transferred in the [GEOMETRY1] NTF record. All coordinates within the data are expressed as strings of five numeric characters. Leading zeros are present to complete the five characters. All coordinates are measured from the local origin, which is the south-west corner of the 50 km by 50 km square. To convert coordinate data to full National Grid coordinates, add the coordinates of the feature to those of the south-west corner of the 50 km by 50 km square. The south-west 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.

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