Class for storing a coordinate reference system (CRS) More...

#include <qgscoordinatereferencesystem.h>

Public Types
enum	CrsType { InternalCrsId, PostgisCrsId, EpsgCrsId }

Public Member Functions
	QgsCoordinateReferenceSystem ()

	QgsCoordinateReferenceSystem (const QString &theDefinition)

	QgsCoordinateReferenceSystem (const long theId, CrsType theType=PostgisCrsId)
	Use this constructor when you want to create a CRS object using a postgis SRID, an EpsgCrsId id or a QGIS CRS_ID. More...

	QgsCoordinateReferenceSystem (const QgsCoordinateReferenceSystem &srs)
	Copy constructor. More...

	~QgsCoordinateReferenceSystem ()

QString	authid () const
	Returns the authority identifier for the CRS, which includes both the authority (eg EPSG) and the CRS number (eg 4326). More...

bool	axisInverted () const
	Returns whether axis is inverted (eg. More...

bool	createFromId (const long theId, CrsType theType=PostgisCrsId)

bool	createFromOgcWmsCrs (const QString &theCrs)
	Sets this CRS to the given OGC WMS-format Coordinate Reference Systems. More...

bool	createFromProj4 (const QString &theProjString)
	Set up this CRS by passing it a proj4 style formatted string. More...

bool	createFromSrid (const long theSrid)
	Set up this CRS by fetching the appropriate information from the sqlite backend. More...

bool	createFromSrsId (const long theSrsId)
	Set up this CRS by fetching the appropriate information from the sqlite backend. More...

bool	createFromString (const QString &theDefinition)
	Set up this CRS from a string definition, by default a WKT definition. More...

bool	createFromUserInput (const QString &theDefinition)
	Set up this CRS from a various text formats. More...

bool	createFromWkt (const QString &theWkt)
	Set up this CRS using a WKT spatial ref sys definition. More...

QString	description () const
	Returns the descriptive name of the CRS, eg "WGS 84" or "GDA 94 / Vicgrid94". More...

QString	ellipsoidAcronym () const
	Returns the ellipsoid acronym for the ellipsoid used by the CRS. More...

long	findMatchingProj ()
	This is a globbing function to try to find a record in the database that matches a CRS defined only by a proj4string. More...

QString	geographicCRSAuthId () const
	Returns auth id of related geographic CRS. More...

bool	geographicFlag () const
	Returns whether the CRS is a geographic CRS. More...

bool	isValid () const
	Returns whether this CRS is correctly initialized and usable. More...

QGis::UnitType	mapUnits () const
	Returns the units for the projection used by the CRS. More...

bool	operator!= (const QgsCoordinateReferenceSystem &theSrs) const
	Overloaded != operator used to compare to CRS's. More...

QgsCoordinateReferenceSystem &	operator= (const QgsCoordinateReferenceSystem &srs)
	Assignment operator. More...

bool	operator== (const QgsCoordinateReferenceSystem &theSrs) const
	Overloaded == operator used to compare to CRS's. More...

long	postgisSrid () const
	Returns PostGIS SRID for the CRS. More...

QString	projectionAcronym () const
	Returns the projection acronym for the projection used by the CRS. More...

bool	readXML (const QDomNode &theNode)
	Restores state from the given Dom node. More...

bool	saveAsUserCRS (const QString &name)
	Save the proj4-string as a custom CRS. More...

void	setValidationHint (const QString &html)
	Set user hint for validation. More...

long	srsid () const
	Returns the SrsId, if available. More...

QString	toProj4 () const
	Returns a Proj4 string representation of this CRS. More...

QString	toWkt () const
	Returns a WKT representation of this CRS. More...

void	validate ()
	Perform some validation on this CRS. More...

QString	validationHint ()
	Get user hint for validation. More...

bool	writeXML (QDomNode &theNode, QDomDocument &theDoc) const
	Stores state to the given Dom node in the given document. More...

Static Public Member Functions
static CUSTOM_CRS_VALIDATION	customSrsValidation ()
	Gets custom function. More...

static QStringList	recentProjections ()
	Returns a list of recently used projections. More...

static void	setCustomSrsValidation (CUSTOM_CRS_VALIDATION f)
	Sets custom function to force valid CRS QGIS uses implementation in QgisGui::customSrsValidation. More...

static void	setupESRIWktFix ()
	Make sure that ESRI WKT import is done properly. More...

static int	syncDb ()
	Update proj.4 parameters in our database from proj.4. More...

Detailed Description

Class for storing a coordinate reference system (CRS)

Note: Since QGIS 2.16 QgsCoordinateReferenceSystem objects are implicitly shared.

Definition at line 52 of file qgscoordinatereferencesystem.h.

Member Enumeration Documentation

◆ CrsType

enum QgsCoordinateReferenceSystem::CrsType

Enumerator
InternalCrsId
PostgisCrsId
EpsgCrsId

Definition at line 56 of file qgscoordinatereferencesystem.h.

Constructor & Destructor Documentation

◆ QgsCoordinateReferenceSystem() [1/4]

QgsCoordinateReferenceSystem::QgsCoordinateReferenceSystem ( )

Definition at line 53 of file qgscoordinatereferencesystem.cpp.

◆ ~QgsCoordinateReferenceSystem()

QgsCoordinateReferenceSystem::~QgsCoordinateReferenceSystem ( )

Definition at line 81 of file qgscoordinatereferencesystem.cpp.

◆ QgsCoordinateReferenceSystem() [2/4]

QgsCoordinateReferenceSystem::QgsCoordinateReferenceSystem ( const QString & theDefinition )

explicit

Constructs a CRS object from a string definition as defined in the createFromString member function (by default a WKT definition).

Parameters

theDefinition A String containing a coordinate reference system definition.

Definition at line 58 of file qgscoordinatereferencesystem.cpp.

◆ QgsCoordinateReferenceSystem() [3/4]

QgsCoordinateReferenceSystem::QgsCoordinateReferenceSystem	(	const long	theId,
		CrsType	theType = `PostgisCrsId`
	)

Use this constructor when you want to create a CRS object using a postgis SRID, an EpsgCrsId id or a QGIS CRS_ID.

Note: We encourage you to use EpsgCrsId, WKT or Proj4 to describe CRS's in your code wherever possible. QGIS CRS_IDs are not guaranteed to be permanent / involatile.

Parameters

theId	The ID no valid for the chosen coordinate system id type
theType	One of the types described in QgsCoordinateReferenceSystem::CrsType

Definition at line 64 of file qgscoordinatereferencesystem.cpp.

◆ QgsCoordinateReferenceSystem() [4/4]

QgsCoordinateReferenceSystem::QgsCoordinateReferenceSystem ( const QgsCoordinateReferenceSystem & srs )

Copy constructor.

Definition at line 70 of file qgscoordinatereferencesystem.cpp.

Member Function Documentation

◆ authid()

QString QgsCoordinateReferenceSystem::authid ( ) const

Returns the authority identifier for the CRS, which includes both the authority (eg EPSG) and the CRS number (eg 4326).

This is the best method to use when showing a very short CRS identifier to a user, eg "EPSG:4326".

Returns: the authority identifier for this CRS

See also: description()

Definition at line 805 of file qgscoordinatereferencesystem.cpp.

◆ axisInverted()

bool QgsCoordinateReferenceSystem::axisInverted ( ) const

Returns whether axis is inverted (eg.

for WMS 1.3) for the CRS.

Returns: true if CRS axis is inverted

Definition at line 371 of file qgscoordinatereferencesystem.cpp.

◆ createFromId()

bool QgsCoordinateReferenceSystem::createFromId	(	const long	theId,
		CrsType	theType = `PostgisCrsId`
	)

Definition at line 85 of file qgscoordinatereferencesystem.cpp.

◆ createFromOgcWmsCrs()

bool QgsCoordinateReferenceSystem::createFromOgcWmsCrs ( const QString & theCrs )

Sets this CRS to the given OGC WMS-format Coordinate Reference Systems.

Returns: false if not given an valid label

Note: this method is expensive. Consider using QgsCRSCache::crsByOgcWmsCrs() instead.

Definition at line 200 of file qgscoordinatereferencesystem.cpp.

◆ createFromProj4()

bool QgsCoordinateReferenceSystem::createFromProj4 ( const QString & theProjString )

Set up this CRS by passing it a proj4 style formatted string.

The string will be parsed and the projection and ellipsoid members set and the remainder of the proj4 string will be stored in the parameters member. The reason for this is so that we can easily present the user with 'natural language' representation of the projection and ellipsoid by looking them up in the srs.bs sqlite database. Also having the ellipse and proj elements stripped out is helpful to speed up globbing queries (see below).

We try to match the proj string to and srsid using the following logic:

perform a whole text search on CRS name (if not null). The CRS name will have been set if this method has been delegated to from createFromWkt.
if the above does not match perform a whole text search on proj4 string (if not null)
if none of the above match convert the proj4 string to an OGR CRS then check if its a geocs or a proj cs (using ogr isGeographic) then sequentially walk through the database (first users qgis.db srs tbl then system srs.db tbl), converting each entry into an ogr srs and using isSame or isSameGeocs (essentially calling the == overloaded operator). We'll try to be smart about this and first parse out the proj and ellpse strings and only check for a match in entities that have the same ellps and proj entries so that it doesn't munch yer cpu so much.

Parameters

theProjString A proj4 format string

Returns: bool TRUE if success else false

Note: this method is expensive. Consider using QgsCRSCache::crsByProj4() instead.

Definition at line 481 of file qgscoordinatereferencesystem.cpp.

◆ createFromSrid()

bool QgsCoordinateReferenceSystem::createFromSrid ( const long theSrid )

Set up this CRS by fetching the appropriate information from the sqlite backend.

First the system level read only srs.db will be checked and then the users ~/.qgis/qgis.db database will be checked for a match.

Note: Any members will be overwritten during this process.

Parameters

theSrid The postgis SRID for the desired spatial reference system.

Definition at line 273 of file qgscoordinatereferencesystem.cpp.

◆ createFromSrsId()

bool QgsCoordinateReferenceSystem::createFromSrsId ( const long theSrsId )

Set up this CRS by fetching the appropriate information from the sqlite backend.

If the srsid is < 100000, only the system srs.db will be checked. If the srsid > 100000 the srs will be retrieved from the ~/.qgis/qgis.db

Note: Any members will be overwritten during this process.

Parameters

theSrsId The QGIS SrsId for the desired spatial reference system.

Returns: bool TRUE if success else false

Note: this method is expensive. Consider using QgsCRSCache::crsBySrsId() instead.

Definition at line 278 of file qgscoordinatereferencesystem.cpp.

◆ createFromString()

bool QgsCoordinateReferenceSystem::createFromString ( const QString & theDefinition )

Set up this CRS from a string definition, by default a WKT definition.

Otherwise the string defines a authority, followed by a colon, followed by the definition. The authority can be one of "epsg", "postgis", "internal" for integer definitions, and "wkt" or "proj4" for string definitions. The implementation of each authority uses the corresponding createFrom... function.

Parameters

theDefinition A String containing a coordinate reference system definition.

Definition at line 106 of file qgscoordinatereferencesystem.cpp.

◆ createFromUserInput()

bool QgsCoordinateReferenceSystem::createFromUserInput ( const QString & theDefinition )

Set up this CRS from a various text formats.

Valid formats: WKT string, "EPSG:n", "EPSGA:n", "AUTO:proj_id,unit_id,lon0,lat0", "urn:ogc:def:crs:EPSG::n", PROJ.4 string, filename (with WKT, XML or PROJ.4 string), well known name (such as NAD27, NAD83, WGS84 or WGS72), ESRI::[WKT string] (directly or in a file), "IGNF:xxx"

For more details on supported formats see OGRSpatialReference::SetFromUserInput() ( http://www.gdal.org/ogr/classOGRSpatialReference.html#aec3c6a49533fe457ddc763d699ff8796 )

Note: this function generates a WKT string using OSRSetFromUserInput() and passes it to createFromWkt() function.

Parameters

theDefinition A String containing a coordinate reference system definition.

Definition at line 150 of file qgscoordinatereferencesystem.cpp.

◆ createFromWkt()

bool QgsCoordinateReferenceSystem::createFromWkt ( const QString & theWkt )

Set up this CRS using a WKT spatial ref sys definition.

The WKT will be converted to a proj4 string using OGR helper functions. After this the SRS databases will be searched for matches. First the system level read only srs.db will be checked and then the users ~/.qgis/qgis.db database will be checked for a match.

Note: Any members will be overwritten during this process.; SRID and EpsgCrsId may be blank if no match can be found on SRS db.

Parameters

theWkt The WKT for the desired spatial reference system.

Returns: bool TRUE if success else false

Note: this method is expensive. Consider using QgsCRSCache::crsByWkt() instead.

Definition at line 398 of file qgscoordinatereferencesystem.cpp.

◆ customSrsValidation()

CUSTOM_CRS_VALIDATION QgsCoordinateReferenceSystem::customSrsValidation ( )

static

Gets custom function.

Note: not available in python bindings

Definition at line 1412 of file qgscoordinatereferencesystem.cpp.

◆ description()

QString QgsCoordinateReferenceSystem::description ( ) const

Returns the descriptive name of the CRS, eg "WGS 84" or "GDA 94 / Vicgrid94".

In most cases this is the best method to use when showing a friendly identifier for the CRS to a user.

Returns: descriptive name of the CRS

Note: an empty string will be returned if the description is not available for the CRS

See also: authid()

Definition at line 810 of file qgscoordinatereferencesystem.cpp.

◆ ellipsoidAcronym()

QString QgsCoordinateReferenceSystem::ellipsoidAcronym ( ) const

Returns the ellipsoid acronym for the ellipsoid used by the CRS.

Returns: the official proj4 acronym for the ellipoid

Note: an empty string will be returned if the ellipsoidAcronym is not available for the CRS

See also: projectionAcronym()

Definition at line 834 of file qgscoordinatereferencesystem.cpp.

◆ findMatchingProj()

long QgsCoordinateReferenceSystem::findMatchingProj ( )

This is a globbing function to try to find a record in the database that matches a CRS defined only by a proj4string.

The goal is to learn what the tbl_srs.srs_id value is for the CRS. Internally the source CRS is converted to an OGR srs object using the proj4string call and then every record in the database that matches projection and ellipsoid will be converted to an OGR srs in turn and compared to the source CRS. There are some gotchas with using ogr isSame() srs comparison, but its more effective than using straight string comparison of proj4params.

Note: The ellipsoid and projection acronyms must be set as well as the proj4string!

Returns: long the SrsId of the matched CRS

Definition at line 1017 of file qgscoordinatereferencesystem.cpp.

◆ geographicCRSAuthId()

QString QgsCoordinateReferenceSystem::geographicCRSAuthId ( ) const

Returns auth id of related geographic CRS.

Definition at line 2155 of file qgscoordinatereferencesystem.cpp.

◆ geographicFlag()

bool QgsCoordinateReferenceSystem::geographicFlag ( ) const

Returns whether the CRS is a geographic CRS.

Returns: true if CRS is geographic, or false if it is a projected CRS

Definition at line 862 of file qgscoordinatereferencesystem.cpp.

◆ isValid()

bool QgsCoordinateReferenceSystem::isValid ( ) const

Returns whether this CRS is correctly initialized and usable.

Definition at line 476 of file qgscoordinatereferencesystem.cpp.

◆ mapUnits()

QGis::UnitType QgsCoordinateReferenceSystem::mapUnits ( ) const

Returns the units for the projection used by the CRS.

Definition at line 867 of file qgscoordinatereferencesystem.cpp.

◆ operator!=()

bool QgsCoordinateReferenceSystem::operator!= ( const QgsCoordinateReferenceSystem & theSrs ) const

Overloaded != operator used to compare to CRS's.

Returns opposite bool value to operator ==

Definition at line 1125 of file qgscoordinatereferencesystem.cpp.

◆ operator=()

QgsCoordinateReferenceSystem & QgsCoordinateReferenceSystem::operator= ( const QgsCoordinateReferenceSystem & srs )

Assignment operator.

Definition at line 75 of file qgscoordinatereferencesystem.cpp.

◆ operator==()

bool QgsCoordinateReferenceSystem::operator== ( const QgsCoordinateReferenceSystem & theSrs ) const

Overloaded == operator used to compare to CRS's.

Internally it will delegate to the equals method described below

Definition at line 1119 of file qgscoordinatereferencesystem.cpp.

◆ postgisSrid()

long QgsCoordinateReferenceSystem::postgisSrid ( ) const

Returns PostGIS SRID for the CRS.

Returns: the PostGIS spatial_ref_sys identifier for this CRS (defaults to 0)

Definition at line 800 of file qgscoordinatereferencesystem.cpp.

◆ projectionAcronym()

QString QgsCoordinateReferenceSystem::projectionAcronym ( ) const

Returns the projection acronym for the projection used by the CRS.

Returns: the official proj4 acronym for the projection family

Note: an empty string will be returned if the projectionAcronym is not available for the CRS

See also: ellipsoidAcronym()

Definition at line 822 of file qgscoordinatereferencesystem.cpp.

◆ readXML()

bool QgsCoordinateReferenceSystem::readXML ( const QDomNode & theNode )

Restores state from the given Dom node.

Parameters

theNode The node from which state will be restored

Returns: bool True on success, False on failure

Definition at line 1144 of file qgscoordinatereferencesystem.cpp.

◆ recentProjections()

QStringList QgsCoordinateReferenceSystem::recentProjections ( )

static

Returns a list of recently used projections.

Returns: list of srsid for recently used projections

Note: added in QGIS 2.7

Definition at line 2171 of file qgscoordinatereferencesystem.cpp.

◆ saveAsUserCRS()

bool QgsCoordinateReferenceSystem::saveAsUserCRS ( const QString & name )

Save the proj4-string as a custom CRS.

Copied from QgsCustomProjectionDialog /// Please refactor into SQL handler !!! ///.

Returns: bool true if success else false

Definition at line 1453 of file qgscoordinatereferencesystem.cpp.

◆ setCustomSrsValidation()

void QgsCoordinateReferenceSystem::setCustomSrsValidation ( CUSTOM_CRS_VALIDATION f )

static

Sets custom function to force valid CRS QGIS uses implementation in QgisGui::customSrsValidation.

Note: not available in python bindings

Definition at line 1407 of file qgscoordinatereferencesystem.cpp.

◆ setupESRIWktFix()

void QgsCoordinateReferenceSystem::setupESRIWktFix ( )

static

Make sure that ESRI WKT import is done properly.

This is required for proper shapefile CRS import when using gdal>= 1.9.

Note: This function is called by createFromUserInput() and QgsOgrProvider::crs(), there is usually no need to call it from elsewhere.; This function sets CPL config option GDAL_FIX_ESRI_WKT to a proper value, unless it has been set by the user through the commandline or an environment variable. For more details refer to OGRSpatialReference::morphFromESRI() .

Definition at line 177 of file qgscoordinatereferencesystem.cpp.

◆ setValidationHint()

void QgsCoordinateReferenceSystem::setValidationHint ( const QString & html )

Set user hint for validation.

Definition at line 1439 of file qgscoordinatereferencesystem.cpp.

◆ srsid()

long QgsCoordinateReferenceSystem::srsid ( ) const

Returns the SrsId, if available.

Returns: the internal sqlite3 srs.db primary key for this srs

See also: postgisSrid()

Definition at line 795 of file qgscoordinatereferencesystem.cpp.

◆ syncDb()

int QgsCoordinateReferenceSystem::syncDb ( )

static

Update proj.4 parameters in our database from proj.4.

Returns: number of updated CRS on success and negative number of failed updates in case of errors.

Definition at line 1694 of file qgscoordinatereferencesystem.cpp.

◆ toProj4()

QString QgsCoordinateReferenceSystem::toProj4 ( ) const

Returns a Proj4 string representation of this CRS.

If proj and ellps keys are found in the parameters, they will be stripped out and the projection and ellipsoid acronyms will be overridden with these.

Returns: Proj4 format string that defines this CRS.

Note: an empty string will be returned if the CRS could not be represented by a Proj4 string

See also: toWkt()

Definition at line 846 of file qgscoordinatereferencesystem.cpp.

◆ toWkt()

QString QgsCoordinateReferenceSystem::toWkt ( ) const

Returns a WKT representation of this CRS.

Returns: string containing WKT of the CRS

See also: toProj4()

Definition at line 1130 of file qgscoordinatereferencesystem.cpp.

◆ validate()

void QgsCoordinateReferenceSystem::validate ( )

Perform some validation on this CRS.

If the sts doesn't validate the default behaviour settings for layers with unknown CRS will be consulted and acted on accordingly. By hell or high water this method will do its best to make sure that this CRS is valid - even if that involves resorting to a hard coded default of geocs:wgs84.

Note: It is not usually necessary to use this function, unless you are trying to force this CRS to be valid.

Definition at line 256 of file qgscoordinatereferencesystem.cpp.

◆ validationHint()

QString QgsCoordinateReferenceSystem::validationHint ( )

Get user hint for validation.

Definition at line 1445 of file qgscoordinatereferencesystem.cpp.

◆ writeXML()

bool QgsCoordinateReferenceSystem::writeXML	(	QDomNode &	theNode,
		QDomDocument &	theDoc
	)		const

Stores state to the given Dom node in the given document.

Below is an example of the generated tag.

<spatialrefsys>
    <proj4>+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs </proj4>
     <srsid>2585</srsid>
     <srid>4326</srid>
     <epsg>4326</epsg>
     <description>WGS 84</description>
     <projectionacronym>longlat</projectionacronym>
     <ellipsoidacronym>WGS84</ellipsoidacronym>
 </spatialrefsys>

Parameters

theNode	The node in which state will be restored
theDoc	The document in which state will be stored

Returns: bool True on success, False on failure

Definition at line 1266 of file qgscoordinatereferencesystem.cpp.

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

/tmp/buildd/qgis-2.18.21+99unstable/src/core/qgscoordinatereferencesystem.h
/tmp/buildd/qgis-2.18.21+99unstable/src/core/qgscoordinatereferencesystem.cpp

Public Types

Public Member Functions

Static Public Member Functions

Detailed Description

Member Enumeration Documentation

◆ CrsType

Constructor & Destructor Documentation

◆ QgsCoordinateReferenceSystem() [1/4]

◆ ~QgsCoordinateReferenceSystem()

◆ QgsCoordinateReferenceSystem() [2/4]

◆ QgsCoordinateReferenceSystem() [3/4]

◆ QgsCoordinateReferenceSystem() [4/4]

Member Function Documentation

◆ authid()

◆ axisInverted()

◆ createFromId()

◆ createFromOgcWmsCrs()

◆ createFromProj4()

◆ createFromSrid()

◆ createFromSrsId()

◆ createFromString()

◆ createFromUserInput()

◆ createFromWkt()

◆ customSrsValidation()

◆ description()

◆ ellipsoidAcronym()

◆ findMatchingProj()

◆ geographicCRSAuthId()

◆ geographicFlag()

◆ isValid()

◆ mapUnits()

◆ operator!=()

◆ operator=()

◆ operator==()

◆ postgisSrid()

◆ projectionAcronym()

◆ readXML()

◆ recentProjections()

◆ saveAsUserCRS()

◆ setCustomSrsValidation()

◆ setupESRIWktFix()

◆ setValidationHint()

◆ srsid()

◆ syncDb()

◆ toProj4()

◆ toWkt()

◆ validate()

◆ validationHint()

◆ writeXML()