- Qt 6.9
- Qt Positioning
- C++ Classes
- QNmeaPositionInfoSource
- Qt 6.9.2 Reference Documentation

# QNmeaPositionInfoSource Class

The QNmeaPositionInfoSource class provides positional information using a NMEA data source. More...

Header: | `#include <QNmeaPositionInfoSource>`
CMake: | `find_package(Qt6 REQUIRED COMPONENTS Positioning)` `target_link_libraries(mytarget PRIVATE Qt6::Positioning)`
qmake: | `QT += positioning`
Inherits: | QGeoPositionInfoSource

- List of all members, including inherited members

## Public Types

enum | UpdateMode { RealTimeMode, SimulationMode }

## Public Functions

| QNmeaPositionInfoSource(QNmeaPositionInfoSource::UpdateMode updateMode, QObject *parent = nullptr)
virtual | ~QNmeaPositionInfoSource()
QIODevice * | device() const
void | setDevice(QIODevice *device)
void | setUserEquivalentRangeError(double uere)
QNmeaPositionInfoSource::UpdateMode | updateMode() const
double | userEquivalentRangeError() const

## Reimplemented Public Functions

virtual QGeoPositionInfoSource::Error | error() const override
virtual QGeoPositionInfo | lastKnownPosition(bool fromSatellitePositioningMethodsOnly = false) const override
virtual int | minimumUpdateInterval() const override
virtual void | setUpdateInterval(int msec) override
virtual QGeoPositionInfoSource::PositioningMethods | supportedPositioningMethods() const override

## Public Slots

virtual void | requestUpdate(int msec = 0) override
virtual void | startUpdates() override
virtual void | stopUpdates() override

## Protected Functions

virtual bool | parsePosInfoFromNmeaData(const char *data, int size, QGeoPositionInfo *posInfo, bool *hasFix)

## Detailed Description

NMEA is a commonly used protocol for the specification of one's global position at a certain point in time. The QNmeaPositionInfoSource class reads NMEA data and uses it to provide positional data in the form of QGeoPositionInfo objects.

A QNmeaPositionInfoSource instance operates in either RealTimeMode or SimulationMode. These modes allow NMEA data to be read from either a live source of positional data, or replayed for simulation purposes from previously recorded NMEA data.

The source of NMEA data is set with setDevice().

Use startUpdates() to start receiving regular position updates and stopUpdates() to stop these updates. If you only require updates occasionally, you can call requestUpdate() to request a single update.

In both cases the position information is received via the positionUpdated() signal and the last known position can be accessed with lastKnownPosition().

QNmeaPositionInfoSource supports reporting the accuracy of the horizontal and vertical position. To enable position accuracy reporting an estimate of the User Equivalent Range Error associated with the NMEA source must be set with setUserEquivalentRangeError().

## Member Type Documentation

### enum QNmeaPositionInfoSource::UpdateMode

Defines the available update modes.

Constant | Value | Description
--- | --- | ---
`QNmeaPositionInfoSource::RealTimeMode` | `1` | Positional data is read and distributed from the data source as it becomes available. Use this mode if you are using a live source of positional data (for example, a GPS hardware device).
`QNmeaPositionInfoSource::SimulationMode` | `2` | The data and time information in the NMEA source data is used to provide positional updates at the rate at which the data was originally recorded. Use this mode if the data source contains previously recorded NMEA data and you want to replay the data for simulation purposes.

## Member Function Documentation

### `[explicit]` QNmeaPositionInfoSource::QNmeaPositionInfoSource(QNmeaPositionInfoSource::UpdateMode updateMode, QObject *parent = nullptr)

Constructs a QNmeaPositionInfoSource instance with the given parent and updateMode.

### `[virtual noexcept]` QNmeaPositionInfoSource::~QNmeaPositionInfoSource()

Destroys the position source.

### QIODevice *QNmeaPositionInfoSource::device() const

Returns the NMEA data source.

See also setDevice().

### `[override virtual]` QGeoPositionInfoSource::Error QNmeaPositionInfoSource::error() const

Reimplements: QGeoPositionInfoSource::error() const.

### `[override virtual]` QGeoPositionInfo QNmeaPositionInfoSource::lastKnownPosition(bool fromSatellitePositioningMethodsOnly = false) const

Reimplements: QGeoPositionInfoSource::lastKnownPosition(bool fromSatellitePositioningMethodsOnly) const.

### `[override virtual]` int QNmeaPositionInfoSource::minimumUpdateInterval() const

Reimplements an access function for property: QGeoPositionInfoSource::minimumUpdateInterval.

### `[virtual protected]` bool QNmeaPositionInfoSource::parsePosInfoFromNmeaData(const char *data, int size, QGeoPositionInfo *posInfo, bool *hasFix)

Parses an NMEA sentence string into a QGeoPositionInfo.

The default implementation will parse standard NMEA sentences. This method should be reimplemented in a subclass whenever the need to deal with non-standard NMEA sentences arises.

The parser reads size bytes from data and uses that information to setup posInfo and hasFix. If hasFix is set to false then posInfo may contain only the time or the date and the time.

Returns true if the sentence was successfully parsed, otherwise returns false and should not modifiy posInfo or hasFix.

### `[override virtual slot]` void QNmeaPositionInfoSource::requestUpdate(int msec = 0)

Reimplements: QGeoPositionInfoSource::requestUpdate(int timeout).

### void QNmeaPositionInfoSource::setDevice(QIODevice *device)

Sets the NMEA data source to device. If the device is not open, it will be opened in ReadOnly mode.

The source device can only be set once and must be set before calling startUpdates() or requestUpdate().

Note: The device must emit QIODevice::readyRead() for the source to be notified when data is available for reading. QNmeaPositionInfoSource does not assume the ownership of the device, and hence does not deallocate it upon destruction.

See also device().

### `[override virtual]` void QNmeaPositionInfoSource::setUpdateInterval(int msec)

Reimplements an access function for property: QGeoPositionInfoSource::updateInterval.

### void QNmeaPositionInfoSource::setUserEquivalentRangeError(double uere)

Sets the User Equivalent Range Error (UERE) to uere. The UERE is used in calculating an estimate of the accuracy of the position information reported by the position info source. The UERE should be set to a value appropriate for the GPS device which generated the NMEA stream.

The true UERE value is calculated from multiple error sources including errors introduced by the satellites and signal propogation delays through the atmosphere as well as errors introduced by the receiving GPS equipment. For details on GPS accuracy see Sam J. Wormley, GPS Errors & Estimating Your Reveiver's Accuracy.

A typical value for UERE is approximately 5.1.

See also userEquivalentRangeError().

### `[override virtual slot]` void QNmeaPositionInfoSource::startUpdates()

Reimplements: QGeoPositionInfoSource::startUpdates().

### `[override virtual slot]` void QNmeaPositionInfoSource::stopUpdates()

Reimplements: QGeoPositionInfoSource::stopUpdates().

### `[override virtual]` QGeoPositionInfoSource::PositioningMethods QNmeaPositionInfoSource::supportedPositioningMethods() const

Reimplements: QGeoPositionInfoSource::supportedPositioningMethods() const.

### QNmeaPositionInfoSource::UpdateMode QNmeaPositionInfoSource::updateMode() const

Returns the update mode.

### double QNmeaPositionInfoSource::userEquivalentRangeError() const

Returns the current User Equivalent Range Error (UERE). The UERE is used in calculating an estimate of the accuracy of the position information reported by the position info source. The default value is NaN which means no accuracy information will be provided.

See also setUserEquivalentRangeError().