Detailed Description

Compute the corrected range from receiver at position Rx, to the GPS satellite given by SatID sat, as well as azimuth, elevation, etc., given a nominal timetag (either received or transmitted time) and a NavLibrary.

The corrected range is a combination of the raw range (geometric range) minus SV clock offsets. The raw range can be written as:

$\rho_{rx}^{sv} = \biggl|\biggl|\mathbf{R}\bigl(-(t_r - t_t)\bigl)\cdot\mathbf{r}^{sv}(t_t) - \mathbf{r}^{rx}(t_r)\biggl|\biggl|$

where,

$\mathbf{R}(\cdot)$ = ECEF frame rotation over a given time interval
$\mathbf{r}^{sv}(t_t)$ = ECEF position of SV at time of signal transmission ( $t_t$

)
$\mathbf{r}^{rx}(t_r)$ = ECEF position of RX at time of signal receive ( $t_r$

)

The different methods in this class represent different methodologies for solving the above equation depending on the available input. See each method for the background in solving for geometric range.

ComputeAtReceiveTime() if only a nominal receive time is known
ComputeAtTransmitTime() if a pseudorange and nominal receive time is known
ComputeAtTransmitSvTime() if a pseudorange and nominal transmit time is known

Definition at line 84 of file EphemerisRange.hpp.

#include <EphemerisRange.hpp>

Public Member Functions
double	ComputeAtReceiveTime (const CommonTime &trNom, const Position &rx, const SatID sat, NavLibrary &navLib, NavSearchOrder order=NavSearchOrder::User, SVHealth xmitHealth=SVHealth::Any, NavValidityType valid=NavValidityType::ValidOnly, const EllipsoidModel &ellipsoid=GPSEllipsoid())

double	ComputeAtTransmitSvTime (const CommonTime &ttNom, const double &pr, const Position &rx, const SatID sat, NavLibrary &navLib, NavSearchOrder order=NavSearchOrder::User, SVHealth xmitHealth=SVHealth::Any, NavValidityType valid=NavValidityType::ValidOnly, const EllipsoidModel &ellipsoid=GPSEllipsoid())

double	ComputeAtTransmitTime (const CommonTime &trNom, const double &pr, const Position &rx, const SatID sat, NavLibrary &navLib, NavSearchOrder order=NavSearchOrder::User, SVHealth xmitHealth=SVHealth::Any, NavValidityType valid=NavValidityType::ValidOnly, const EllipsoidModel &ellipsoid=GPSEllipsoid())

double	ComputeAtTransmitTime (const CommonTime &trNom, const Position &rx, const SatID sat, NavLibrary &navLib, NavSearchOrder order=NavSearchOrder::User, SVHealth xmitHealth=SVHealth::Any, NavValidityType valid=NavValidityType::ValidOnly, const EllipsoidModel &ellipsoid=GPSEllipsoid())

	CorrectedEphemerisRange ()
	Default constructor. More...

Public Attributes
double	azimuth

double	azimuthGeodetic

Triple	cosines

double	elevation

double	elevationGeodetic

vshort	health

vshort	iodc
	The IODC of the GPS LNAV ephemeris, invalid for other GNSSes. More...

double	rawrange
	The computed raw (geometric) range in meters. More...

double	relativity
	The relativity correction in meters. More...

double	svclkbias
	The satellite clock bias in meters. More...

double	svclkdrift
	The satellite clock drift in m/s. More...

Xvt	svPosVel
	The satellite position (m) and velocity (m/s) in ECEF coordinates. More...

CommonTime	transmit
	The computed transmit time of the signal. More...

Private Member Functions
void	updateCER (const Position &rx)

Constructor & Destructor Documentation

◆ CorrectedEphemerisRange()

gnsstk::CorrectedEphemerisRange::CorrectedEphemerisRange ( )

inline

Default constructor.

Definition at line 88 of file EphemerisRange.hpp.

Member Function Documentation

◆ ComputeAtReceiveTime()

double gnsstk::CorrectedEphemerisRange::ComputeAtReceiveTime	(	const CommonTime &	trNom,
		const Position &	rx,
		const SatID	sat,
		NavLibrary &	navLib,
		NavSearchOrder	order = `NavSearchOrder::User`,
		SVHealth	xmitHealth = `SVHealth::Any`,
		NavValidityType	valid = `NavValidityType::ValidOnly`,
		const EllipsoidModel &	ellipsoid = `GPSEllipsoid()`
	)

Compute the corrected range at RECEIVE time (receiver time frame), from rx to sat at trNom.

Note: This does not account for a RX clock bias that might be present in trNom. If a RX clock bias is known, adjust the input timestamp accordingly before calling this method.

This method uses an iterative solution solving for the geometric range and the time of flight. An initial guess is used for the time of flight, a geometric range is computed, and a new time of flight is computed with the relationship of $\tau = \frac{\rho_{rx}^{sv}}{c}$

Parameters

[in]	trNom	Nominal receive time ( $\widetilde{t}_r^{rx}$ ).
[in]	rx	Receiver position ( $\mathbf{r}^{sv}(t_t)$ ).
[in]	sat	Satellite ID to get the position for.
[in]	navLib	The navigation data library to use for looking up satellite XVT.
[in]	order	Specify whether to search by receiver behavior or by nearest to when in time.
[in]	xmitHealth	The desired health status of the satellite transmitting the nav data.
[in]	valid	Specify whether to search only for valid or invalid messages, or both.
[in]	ellipsoid	Ellipsoid model to provide an ECEF rotation rate.

Returns: The corrected range from rx to sat at trNom.

Definition at line 65 of file EphemerisRange.cpp.

◆ ComputeAtTransmitSvTime()

double gnsstk::CorrectedEphemerisRange::ComputeAtTransmitSvTime	(	const CommonTime &	ttNom,
		const double &	pr,
		const Position &	rx,
		const SatID	sat,
		NavLibrary &	navLib,
		NavSearchOrder	order = `NavSearchOrder::User`,
		SVHealth	xmitHealth = `SVHealth::Any`,
		NavValidityType	valid = `NavValidityType::ValidOnly`,
		const EllipsoidModel &	ellipsoid = `GPSEllipsoid()`
	)

Compute the corrected range at TRANSMIT time (SV time frame), from rx to sat at ttNom.

A similar methodology to ComputeAtTransmitTime but uses the SV's nominal transmit time and a pseudorange to estimate the receive time then geometric range.

Parameters

[in]	ttNom	Nominal transmit time ( $\widetilde{t}_t^{sv}$ ).
[in]	pr	Measured pseudorange to initialize time-of-flight ( ).
[in]	rx	Receiver position ( $\mathbf{r}^{sv}(t_t)$ ).
[in]	sat	Satellite ID to get the position for.
[in]	navLib	The navigation data library to use for looking up satellite XVT.
[in]	order	Specify whether to search by receiver behavior or by nearest to when in time.
[in]	xmitHealth	The desired health status of the satellite transmitting the nav data.
[in]	valid	Specify whether to search only for valid or invalid messages, or both.
[in]	ellipsoid	Ellipsoid model to provide an ECEF rotation rate.

Returns: The corrected range from rx to sat at ttNom.

Definition at line 165 of file EphemerisRange.cpp.

◆ ComputeAtTransmitTime() [1/2]

double gnsstk::CorrectedEphemerisRange::ComputeAtTransmitTime	(	const CommonTime &	trNom,
		const double &	pr,
		const Position &	rx,
		const SatID	sat,
		NavLibrary &	navLib,
		NavSearchOrder	order = `NavSearchOrder::User`,
		SVHealth	xmitHealth = `SVHealth::Any`,
		NavValidityType	valid = `NavValidityType::ValidOnly`,
		const EllipsoidModel &	ellipsoid = `GPSEllipsoid()`
	)

Compute the corrected range at TRANSMIT time (receiver time frame) from rx to sat at trNom.

Note: The name of the method is slightly misleading. This uses a RX's nominal receive time to compute the distance between a RX at nominal receive time and an SV at transmit time.

This uses a simple rearrangement of the RX pseudorange equation to determine a nominal time of signal transmission ( $t_t$ ).

$\begin{eqnarray*} p &=& c(\widetilde{t}_r^{rx} - \widetilde{t}_t^{sv}) \\ \Rightarrow \widetilde{t}_t^{sv} &=& \widetilde{t}_r^{rx} - p/c \end{eqnarray*}$

The nominal transmission time is corrected with SV clock offsets to compute the true transmission time.

$\begin{eqnarray*} t_t &=& \widetilde{t}_t^{sv} - dt^{sv}(\widetilde{t}_t^{sv}) \\ &=& \widetilde{t}_r^{rx} - p/c - dt^{sv}(\widetilde{t}_t^{sv}) \end{eqnarray*}$

Note that any RX clock bias drops out as the bias is present in both the RX's timestamp ( $\widetilde{t}_r^{rx}$ ) and in the pseudorange. With the transmit time computed, a geometric range is computed using the equation described in class description.

Parameters

[in]	trNom	Nominal recieve time ( $\widetilde{t}_r^{rx}$ ).
[in]	pr	Measured pseudorange to initialize time-of-flight ( ).
[in]	rx	Receiver position ( $\mathbf{r}^{sv}(t_t)$ ).
[in]	sat	Satellite ID to get the position for.
[in]	navLib	The navigation data library to use for looking up satellite XVT.
[in]	order	Specify whether to search by receiver behavior or by nearest to when in time.
[in]	xmitHealth	The desired health status of the satellite transmitting the nav data.
[in]	valid	Specify whether to search only for valid or invalid messages, or both.
[in]	ellipsoid	Ellipsoid model to provide an ECEF rotation rate.

Returns: The corrected range from rx to sat at trNom.

Definition at line 102 of file EphemerisRange.cpp.

◆ ComputeAtTransmitTime() [2/2]

double gnsstk::CorrectedEphemerisRange::ComputeAtTransmitTime	(	const CommonTime &	trNom,
		const Position &	rx,
		const SatID	sat,
		NavLibrary &	navLib,
		NavSearchOrder	order = `NavSearchOrder::User`,
		SVHealth	xmitHealth = `SVHealth::Any`,
		NavValidityType	valid = `NavValidityType::ValidOnly`,
		const EllipsoidModel &	ellipsoid = `GPSEllipsoid()`
	)

Compute the corrected range at TRANSMIT time (receiver time frame), from rx to sat at trNom.

Note: The name of the method is slightly misleading. This uses a RX's apparent receive time to compute the distance between a RX at apparent receive time and an SV at transmit time.

Note: This doesn't use a pseudorange to initialize the time-of-flight computation; however note that this could be problematic since the measured pseudorange includes the rx clock bias while this does not; prefer the version with measured pseudorange input.

This uses the same methodology as ComputeAtTransmitTime with the pseudorange input, but instead of a using a direct pseudorange obseravation one is generated using the provided receiver position and the SV's position at the nominal receive time.

Parameters

[in]	trNom	Nominal receive time ( $\widetilde{t}_r^{rx}$ ).
[in]	rx	Receiver position ( $\mathbf{r}^{sv}(t_t)$ ).
[in]	sat	Satellite ID to get the position for.
[in]	navLib	The navigation data library to use for looking up satellite XVT.
[in]	order	Specify whether to search by receiver behavior or by nearest to when in time.
[in]	xmitHealth	The desired health status of the satellite transmitting the nav data.
[in]	valid	Specify whether to search only for valid or invalid messages, or both.
[in]	ellipsoid	Ellipsoid model to provide an ECEF rotation rate.

Returns: The corrected range from rx to sat at trNom.

Definition at line 133 of file EphemerisRange.cpp.

◆ updateCER()

void gnsstk::CorrectedEphemerisRange::updateCER ( const Position & rx )

private

Definition at line 200 of file EphemerisRange.cpp.

Member Data Documentation

◆ azimuth

double gnsstk::CorrectedEphemerisRange::azimuth

The satellite azimuth (spheroidal), as seen at the receiver, in degrees.

Definition at line 266 of file EphemerisRange.hpp.

◆ azimuthGeodetic

double gnsstk::CorrectedEphemerisRange::azimuthGeodetic

The satellite azimuth (geodetic), as seen at the receiver, in degrees.

Definition at line 272 of file EphemerisRange.hpp.

◆ cosines

Triple gnsstk::CorrectedEphemerisRange::cosines

The direction cosines of the satellite, as seen at the receiver (XYZ).

Definition at line 277 of file EphemerisRange.hpp.

◆ elevation

double gnsstk::CorrectedEphemerisRange::elevation

The satellite elevation (spheroidal), as seen at the receiver, in degrees.

Definition at line 263 of file EphemerisRange.hpp.

◆ elevationGeodetic

double gnsstk::CorrectedEphemerisRange::elevationGeodetic

The satellite elevation (geodetic), as seen at the receiver, in degrees.

Definition at line 269 of file EphemerisRange.hpp.

◆ health

vshort gnsstk::CorrectedEphemerisRange::health

The health bits from the GPS LNAV ephemeris, invalid for other GNSSes

Definition at line 284 of file EphemerisRange.hpp.

◆ iodc

vshort gnsstk::CorrectedEphemerisRange::iodc

The IODC of the GPS LNAV ephemeris, invalid for other GNSSes.

Definition at line 281 of file EphemerisRange.hpp.

◆ rawrange

double gnsstk::CorrectedEphemerisRange::rawrange

The computed raw (geometric) range in meters.

Definition at line 254 of file EphemerisRange.hpp.

◆ relativity

double gnsstk::CorrectedEphemerisRange::relativity

The relativity correction in meters.

Definition at line 260 of file EphemerisRange.hpp.

◆ svclkbias

double gnsstk::CorrectedEphemerisRange::svclkbias

The satellite clock bias in meters.

Definition at line 256 of file EphemerisRange.hpp.

◆ svclkdrift

double gnsstk::CorrectedEphemerisRange::svclkdrift

The satellite clock drift in m/s.

Definition at line 258 of file EphemerisRange.hpp.

◆ svPosVel

Xvt gnsstk::CorrectedEphemerisRange::svPosVel

The satellite position (m) and velocity (m/s) in ECEF coordinates.

Definition at line 279 of file EphemerisRange.hpp.

◆ transmit

CommonTime gnsstk::CorrectedEphemerisRange::transmit

The computed transmit time of the signal.

Definition at line 274 of file EphemerisRange.hpp.

The documentation for this class was generated from the following files:

Detailed Description

Public Member Functions

Public Attributes

Private Member Functions

Constructor & Destructor Documentation

◆ CorrectedEphemerisRange()

Member Function Documentation

◆ ComputeAtReceiveTime()

◆ ComputeAtTransmitSvTime()

◆ ComputeAtTransmitTime() [1/2]

◆ ComputeAtTransmitTime() [2/2]

◆ updateCER()

Member Data Documentation

◆ azimuth

◆ azimuthGeodetic

◆ cosines

◆ elevation

◆ elevationGeodetic

◆ health

◆ iodc

◆ rawrange

◆ relativity

◆ svclkbias

◆ svclkdrift

◆ svPosVel

◆ transmit