Navigation Data (nav.dat & earth_nav.dat) File Format Specification

This information is historic and only relevant to X-Plane 10 and earlier

REVISION HISTORY

12 Nov 2015 Update to move spec to developer site
7 May 2009 Spec converted to this new format to support new web site (http://data.x-plane.com).
8 Sept 2009 Error in usage of row type 13 fixed in “applicability” section below.
31 May 2010 Corrected error in specification of VOR and localizer radio frequencies. Added elevations to NDB spec. Corrected references to apt.dat.
29 July 2011 Fixed minor error in definition of nav-aid frequencies
27 Oct 2011 Fixed minor error in definition of glideslope approach angle
8 July 2012 Corrected error in definition of nav-aid ranges

This specification (XP NAV810) is supported in X-Plane 8.10 to X-Plane 10.52. It is identified in the data files as “810 Version” on the second row of the file. The prior specification for airport data was XP NAV740, which is recommended for X-Plane 7.40 – 8.09.

Changes in the spec for XP NAV810 were:

A new row code for DMEs (13) for which the frequency display will be shown on X-Planes charts. DMEs with a row type 12 will have their frequency display suppressed on X-Plane’s chart to prevent clutter (such DMEs are usually co-located with a VOR or an ILS).

OVERVIEW & SCOPE

This specification defines all radio navigation data for X-Plane, including NDBs, VORs (inc. VORTACs and VOR-DMEs), and ILS components (localisers, glideslopes, marker beacons). The effect of this data is to:

  • Allow these radio navigation facilities to be used when flying in X-Plane.
  • Display the navigation facilities on X-Plane’s chart.
  • Render objects in the X-Plane scenery system to represent each facility

BASIC CONCEPTS

  • Latitudes and longitudes are described in a decimal notation (eg. 20.12345678).
    • A latitude of 50 degrees 30 minutes south would be defined as -50.50000000
  • North latitudes and east longitudes are positive. South latitudes and west longitudes are negative.
  • All headings are referenced to true north (not magnetic north). X-Plane has an internal model of magnetic variation

FILE CHARACTERISTICS

The earth_nav.dat (and nav.dat) files are plain text files:

  • Fields in the data can be separated by one or more white space characters.
  • By default, the files are generated so that rows of data are consistently aligned, but this is not required.

FILE STRUCTURE

The navigation data can be edited in X-Plane in the “Location | Local Map” view, and by clicking on the “edit” button at the top of the screen. If data is changed here, then X-Plane will ask for confirmation that the new data should be saved when quitting X-Plane. This will ensure that all structural requirements listed here for airport data are met.

[Note that the current version of X-Plane displays headings for an ILS in magnetic degrees on this screen, but that this data is converted to a true heading when the data is saved to earth_nav.dat.]

In common with most other X-Plane data file specification, header rows of data define the origin (PC or Mac) of a particular copy of a file, and define the file specification version. The file specification may be followed by a reference to a sequential release data cycle and build number for the data, and a copyright message:

I
810 Version - data cycle 2009.01, build 20081054, metadata NavXP810. Copyright © 2009, Robin A. Peel (robin@xsquawkbox.net)...

The complete copyright message should be left intact if you redistribute this data. The GNU GPL (general public License) under which this data is released is
designed to encourage modifications, enhancements and redistribution, even in commercial derivative products.

Subsequent rows of data define each nav-aid. Sequence is not important, but by default this file is sorted by row code, then by nav-aid name.

The file is terminated by a ‘99’.

ROW CODES

Each row of data begins with an integer code that defines the type of data:

Row Code Meaning Comment
2 NDB (Non-Directional Beacon) Includes NDB component of Locator Outer Markers (LOM)
3 VOR (including VOR-DME and VORTACs) Includes VORs, VOR-DMEs and VORTACs
4 Localiser component of an ILS (Instrument Landing System)
5 Localiser component of a localiser-only approach Includes for LDAs and SDFs
6 Glideslope component of an ILS Frequency shown is paired frequency, not the DME channel
7 Outer markers (OM) for an ILS Includes outer maker component of LOMs
8 Middle markers (MM) for an ILS
9 Inner markers (IM) for an ILS
12 DME, including the DME component of an ILS, VORTAC or VOR-DME Frequency display suppressed on X-Plane’s charts
13 Stand-alone DME, or the DME component of an NDB-DME Frequency will displayed on X-Plane’s charts

EXAMPLE DATA

Here is some example data for the Seattle, Washington, USA area (note the separate data row for the DME component of the Seattle VORTAC):

2 47.63252778 -122.38952778 0 362 50 0.0 BF NOLLA NDB
3 47.43538889 -122.30961111 354 11680 130 19.0 SEA SEATTLE VORTAC
4 47.42939200 -122.30805600 338 11030 18 180.343 ISNQ KSEA 16L ILS-cat-I
6 47.46081700 -122.30939400 425 11030 10 300180.343 ISNQ KSEA 16L GS
8 47.47223300 -122.31102500 433 0 0 180.343 ---- KSEA 16L MM
12 47.43433300 -122.30630000 369 11030 18 0.000 ISNQ KSEA 16L DME-ILS
12 47.43538889 -122.30961111 354 11680 130 0.0 SEA SEATTLE VORTAC DME

DEFINITION OF DATA FIELDS

For a complete table of example definitions, download the NAV810 Spec pdf file.

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