QGIS API Documentation  2.15.0-Master (972fc9f)
Public Types | Public Member Functions | Static Public Member Functions | List of all members
QgsCoordinateReferenceSystem Class Reference

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...
 
QgsCoordinateReferenceSystemoperator= (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

Enumerator
InternalCrsId 
PostgisCrsId 
EpsgCrsId 

Definition at line 56 of file qgscoordinatereferencesystem.h.

Constructor & Destructor Documentation

QgsCoordinateReferenceSystem::QgsCoordinateReferenceSystem ( )

Definition at line 53 of file qgscoordinatereferencesystem.cpp.

QgsCoordinateReferenceSystem::~QgsCoordinateReferenceSystem ( )

Definition at line 81 of file qgscoordinatereferencesystem.cpp.

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
theDefinitionA String containing a coordinate reference system definition.

Definition at line 58 of file qgscoordinatereferencesystem.cpp.

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
theIdThe ID no valid for the chosen coordinate system id type
theTypeOne of the types described in QgsCoordinateReferenceSystem::CrsType

Definition at line 64 of file qgscoordinatereferencesystem.cpp.

QgsCoordinateReferenceSystem::QgsCoordinateReferenceSystem ( const QgsCoordinateReferenceSystem srs)

Copy constructor.

Definition at line 70 of file qgscoordinatereferencesystem.cpp.

Member Function Documentation

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 801 of file qgscoordinatereferencesystem.cpp.

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 368 of file qgscoordinatereferencesystem.cpp.

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

Definition at line 85 of file qgscoordinatereferencesystem.cpp.

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.

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
theProjStringA proj4 format string
Returns
bool TRUE if success else false
Note
this method is expensive. Consider using QgsCRSCache::crsByProj4() instead.

Definition at line 477 of file qgscoordinatereferencesystem.cpp.

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
theSridThe postgis SRID for the desired spatial reference system.

Definition at line 270 of file qgscoordinatereferencesystem.cpp.

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
theSrsIdThe QGIS SrsId for the desired spatial reference system.
Returns
bool TRUE if success else false

Definition at line 275 of file qgscoordinatereferencesystem.cpp.

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
theDefinitionA String containing a coordinate reference system definition.

Definition at line 106 of file qgscoordinatereferencesystem.cpp.

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
theDefinitionA String containing a coordinate reference system definition.

Definition at line 150 of file qgscoordinatereferencesystem.cpp.

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
theWktThe WKT for the desired spatial reference system.
Returns
bool TRUE if success else false

Definition at line 394 of file qgscoordinatereferencesystem.cpp.

CUSTOM_CRS_VALIDATION QgsCoordinateReferenceSystem::customSrsValidation ( )
static

Gets custom function.

Note
not available in python bindings

Definition at line 1406 of file qgscoordinatereferencesystem.cpp.

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 806 of file qgscoordinatereferencesystem.cpp.

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 830 of file qgscoordinatereferencesystem.cpp.

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 1011 of file qgscoordinatereferencesystem.cpp.

QString QgsCoordinateReferenceSystem::geographicCRSAuthId ( ) const

Returns auth id of related geographic CRS.

Definition at line 2144 of file qgscoordinatereferencesystem.cpp.

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 858 of file qgscoordinatereferencesystem.cpp.

bool QgsCoordinateReferenceSystem::isValid ( ) const

Returns whether this CRS is correctly initialized and usable.

Definition at line 472 of file qgscoordinatereferencesystem.cpp.

QGis::UnitType QgsCoordinateReferenceSystem::mapUnits ( ) const

Returns the units for the projection used by the CRS.

Definition at line 863 of file qgscoordinatereferencesystem.cpp.

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

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

Returns opposite bool value to operator ==

Definition at line 1119 of file qgscoordinatereferencesystem.cpp.

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

Assignment operator.

Definition at line 75 of file qgscoordinatereferencesystem.cpp.

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 1113 of file qgscoordinatereferencesystem.cpp.

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 796 of file qgscoordinatereferencesystem.cpp.

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 818 of file qgscoordinatereferencesystem.cpp.

bool QgsCoordinateReferenceSystem::readXML ( const QDomNode theNode)

Restores state from the given Dom node.

Parameters
theNodeThe node from which state will be restored
Returns
bool True on success, False on failure

Definition at line 1138 of file qgscoordinatereferencesystem.cpp.

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 2160 of file qgscoordinatereferencesystem.cpp.

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 1447 of file qgscoordinatereferencesystem.cpp.

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 1401 of file qgscoordinatereferencesystem.cpp.

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.

void QgsCoordinateReferenceSystem::setValidationHint ( const QString html)

Set user hint for validation.

Definition at line 1433 of file qgscoordinatereferencesystem.cpp.

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 791 of file qgscoordinatereferencesystem.cpp.

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 1688 of file qgscoordinatereferencesystem.cpp.

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 842 of file qgscoordinatereferencesystem.cpp.

QString QgsCoordinateReferenceSystem::toWkt ( ) const

Returns a WKT representation of this CRS.

Returns
string containing WKT of the CRS
See also
toProj4()

Definition at line 1124 of file qgscoordinatereferencesystem.cpp.

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 253 of file qgscoordinatereferencesystem.cpp.

QString QgsCoordinateReferenceSystem::validationHint ( )

Get user hint for validation.

Definition at line 1439 of file qgscoordinatereferencesystem.cpp.

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.

1 <spatialrefsys>
2  <proj4>+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs </proj4>
3  <srsid>2585</srsid>
4  <srid>4326</srid>
5  <epsg>4326</epsg>
6  <description>WGS 84</description>
7  <projectionacronym>longlat</projectionacronym>
8  <ellipsoidacronym>WGS84</ellipsoidacronym>
9  </spatialrefsys>
Parameters
theNodeThe node in which state will be restored
theDocThe document in which state will be stored
Returns
bool True on success, False on failure

Definition at line 1260 of file qgscoordinatereferencesystem.cpp.


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