Land-Line NTF file (NTF)

Long name NTF Land-Line
Short name NTFL
File extension(s) .ntf

Land-Line data is an enhanced vector data set, where features are represented as points and lines that are digitised and specifically coded to show differing features. It is not a structured data set and, as such, does not contain defined polygons.

Land-Line can be supplied in two different file formats. These are:
  1. National Transfer Format (NTF)
  2. Drawing Exchange File format (DXF)
NTF file are supported by the GDB library for import and view. Three vector segments are used to display NTF file's three data set:
  1. point
  2. line
  3. text
Each contains different attributes with different feature.

Structure of features

The structure of each different feature is as follows:

  1. Points - these consist of:
    • a Point Record [POINTREC] 15
    • a Geometry Record [GEOMETRY1] 21
    • and can have an associated Attribute Record [ATTREC] 14, which contains a measurement for variable sized symbols
  2. Lines - these consist of:
    • a Line Record [LINEREC] 23
    • and a Geometry Record [GEOMETRY1] 21
    • and maybe one or more Continuation Records[CONTREC] 00 to extend the Geometry Record
  3. Text - this consists of:
    • a Name Record [NAMEREC] 11
    • a Name Position Record [NAMPOSTN] 12
    • and a Geometry Record [GEOMETRY1] 21

Coordinate referencing system

Abbreviated National Grid coordinates are supplied and are given in centimetres. The coordinates have a field width of 6, not the NTF default width of 10. Full National Grid coordinates are calculated by using the {XY_MULT}, {X_ORIG} and {Y_ORIG} values in the Section Header Record [SECHREC] 07, and the conversion formulae below:

X = ({XY_MULT} x {X_COORD}) + {X_ORIG}
Y = ({XY_MULT} x {Y_COORD}) + {Y_ORIG}

where {X_ORIG} and {Y_ORIG} are additive constants, always added to {X_COORD} and {Y_COORD} respectively, whilst {XY_MULT} is a multiplication factor applied to coordinates before the addition of {X_ORIG} and {Y_ORIG}. Negative coordinate values may be carried in {X_COORD}, {Y_COORD}. In each case, the minus sign appears as the first character of the field.

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

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