Generic position File

The generic position file is used to provide external absolute position that are injected into the navigation filter as position measurements, in order to constrain and correct the estimated trajectory.

The external position can originate from various sources such as visual positioning systems, radio-based localization, or any alternative PNT system capable of providing absolute position measurements.

GNSS PVT data

This file format should be used only for non GNSS position sources. For GNSS please refer to the GNSS PVT File which uses dedicated error models for GNSS enabling higher accuracy and robustness.

Conventions

Position is expressed in geodetic coordinates:

Latitude (degrees)
Longitude (degrees)
Ellipsoid Height (meters)

The associated uncertainty is expressed as a 3×3 covariance matrix in the local geodetic frame (Latitude, Longitude, Height).

ASCII Position Format

The file format is composed of an optional header followed by position data stored line by line. If Qinertia doesn't find the header, the default configuration values are used. The file can use either Windows, Unix or Linux line ending conventions and should use UTF-8 encoding.

ASCII header

The header is used to configure how Qinertia should parse and import the file. The header always starts with the $qpos magic keyword to identify it. Then each parameter can be set using a succession of <param>:<value> pairs stored line by line.

If there is no header or the parameter is not present in the file, Qinertia will use the default value that is indicated in bold.

Param Optional Description

$version

Position ASCII file format version, should be set to 1

$timeSource

Position data time stamp format:

gps: Seconds from 6 January 1980 (no leap second)
gpsTow: GPS time of week in seconds
utcIso: ISO 6801 (e.g. 2020-06-19T11:50:04.535Z)
unix: Seconds from 1 January 1970 (UTC time)

$gpsWeekNumber

GPS week number to use in case $timeSource is gpsTow

If gpsTow is selected this parameter is mandatory and has no default value.

ASCII data

The ASCII Position data part is a succession of time stamped position measurement stored line per line. Each column field is separated by a tabulation '\t' or semicolon ';' character.

Field	Type	Unit	Description
`Timestamp`	-	-	The position data time stamp expressed in the format specified by the `$timeSource` header field.
`Latitude`	double	°	Geodetic latitude
`Longitude`	double	°	Geodetic longitude
`Ellipsoid height`	double	m	Ellipsoid height
`Latitude Variance`	double	m²	Variance of latitude
`Longitude Variance`	double	m²	Variance of longitude
`Height Variance`	double	m²	Variance of height
`Latitude/Longitude Covariance`	double	m²	Covariance between latitude and longitude (default = 0.0)
`Latitude/Height Covariance`	double	m²	Covariance between latitude and height (default = 0.0)
`Longitude/Height Covariance`	double	m²	Covariance between longitude and height (default = 0.0)

Example

The example below shows a few Position measurements with the file header:

$qpos
$version:1
$timeSource:utcIso 
2025-02-24T15:47:59.020Z;48.909480511;2.167259805;97.006;0.026;0.028;0.023;0.1;0.2;0.3
2025-02-24T15:47:59.040Z;48.909480461;2.167260831;97.007;0.026;0.028;0.023;0.1;0.2;0.3
2025-02-24T15:47:59.060Z;48.909480405;2.167261857;97.008;0.025;0.028;0.023;0.1;0.2;0.3
2025-02-24T15:47:59.080Z;48.909480343;2.167262883;97.008;0.025;0.028;0.023;0.1;0.2;0.3
2025-02-24T15:47:59.100Z;48.909480274;2.167263908;97.009;0.025;0.027;0.023;0.1;0.2;0.3
2025-02-24T15:47:59.120Z;48.909480199;2.167264932;97.010;0.025;0.027;0.023;0.1;0.2;0.3
2025-02-24T15:47:59.140Z;48.909480118;2.167265956;97.011;0.024;0.027;0.022;0.1;0.2;0.3
2025-02-24T15:47:59.160Z;48.909480030;2.167266978;97.012;0.024;0.026;0.022;0.1;0.2;0.3
2025-02-24T15:47:59.180Z;48.909479935;2.167268000;97.012;0.024;0.026;0.022;0.1;0.2;0.3
2025-02-24T15:47:59.200Z;48.909479834;2.167269020;97.013;0.024;0.026;0.022;0.1;0.2;0.3
2025-02-24T15:47:59.220Z;48.909479727;2.167270040;97.013;0.024;0.026;0.022;0.1;0.2;0.3
2025-02-24T15:47:59.240Z;48.909479615;2.167271058;97.014;0.023;0.025;0.022;0.1;0.2;0.3

TEXT

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