Class for storing a coordinate reference system (CRS)
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#include <qgscoordinatereferencesystem.h>
Detailed Description
Class for storing a coordinate reference system (CRS)
Member Enumeration Documentation
- Enumerator:
InternalCrsId |
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PostgisCrsId |
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EpsgCrsId |
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Constructor & Destructor Documentation
QgsCoordinateReferenceSystem::QgsCoordinateReferenceSystem |
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QgsCoordinateReferenceSystem::~QgsCoordinateReferenceSystem |
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QgsCoordinateReferenceSystem::QgsCoordinateReferenceSystem |
( |
QString |
theDefinition | ) |
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explicit |
Constructs a CRS object from a string definition as defined in the createFromString member function (by default a WKT definition).
- Parameters
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theDefinition | A String containing a coordinate reference system definition. |
QgsCoordinateReferenceSystem::QgsCoordinateReferenceSystem |
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const long |
theId, |
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CrsType |
theType = PostgisCrsId |
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) |
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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. QGSI CRS_IDs are not guaranteed to be permanent / involatile.
- Parameters
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Member Function Documentation
QString QgsCoordinateReferenceSystem::authid |
( |
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const |
Get the authority identifier for this srs
- Returns
- QString the Authority identifier for this srs
bool QgsCoordinateReferenceSystem::axisInverted |
( |
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const |
return if axis is inverted (eg. for WMS 1.3)
- Returns
- bool Whether this is crs axis is inverted
bool QgsCoordinateReferenceSystem::createFromId |
( |
const long |
theId, |
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CrsType |
theType = PostgisCrsId |
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) |
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bool QgsCoordinateReferenceSystem::createFromOgcWmsCrs |
( |
QString |
theCrs | ) |
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Set up this CRS from the given OGC CRS.
Sets this CRS to the given OGC WMS-format Coordinate Reference Systems.
- Return values
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false | if not given an valid label |
bool QgsCoordinateReferenceSystem::createFromProj4 |
( |
const QString & |
theProjString | ) |
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Set up this srs 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 srs name (if not null). The srs 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
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theProjString | A proj4 format string |
- Returns
- bool TRUE if success else false
bool QgsCoordinateReferenceSystem::createFromSrid |
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const long |
theSrid | ) |
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Set up this srs 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
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theSrid | The postgis SRID for the desired spatial reference system. |
bool QgsCoordinateReferenceSystem::createFromSrsId |
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const long |
theSrsId | ) |
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Set up this srs 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
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theSrsId | The QGIS SrsId for the desired spatial reference system. |
- Returns
- bool TRUE if success else false
bool QgsCoordinateReferenceSystem::createFromString |
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const QString & |
theDefinition | ) |
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Set up this srs 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
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theDefinition | A String containing a coordinate reference system definition. |
bool QgsCoordinateReferenceSystem::createFromUserInput |
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const QString & |
theDefinition | ) |
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Set up this srs 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.
@param theDefinition A String containing a coordinate reference system definition.
bool QgsCoordinateReferenceSystem::createFromWkt |
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const QString & |
theWkt | ) |
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Set up this srs using a Wkt spatial ref sys definition. The wkt will be converted to a proj4 string using OGR helper functions. After this the srs databasses 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.
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SRID and EpsgCrsId may be blank if no match can be found on srs db.
- Parameters
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theWkt | The Wkt for the desired spatial reference system. |
- Returns
- bool TRUE if success else false
Gets custom function.
- Note
- not available in python bindings
QString QgsCoordinateReferenceSystem::description |
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const |
Get the Description
- Returns
- QString the Description A textual description of the srs.
- Note
- A zero length string will be returned if the description is uninitialised
QString QgsCoordinateReferenceSystem::ellipsoidAcronym |
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const |
Get the Ellipsoid Acronym
- Returns
- QString theEllipsoidAcronym The official proj4 acronym for the ellipoid
- Note
- A zero length string will be returned if the ellipsoidAcronym is uninitialised
long QgsCoordinateReferenceSystem::findMatchingProj |
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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
QString QgsCoordinateReferenceSystem::geographicCRSAuthId |
( |
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const |
Returns auth id of related geographic CRS.
bool QgsCoordinateReferenceSystem::geographicFlag |
( |
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const |
Get this Geographic? flag
- Returns
- bool theGeoFlag Whether this is a geographic or projected coordinate system
bool QgsCoordinateReferenceSystem::isValid |
( |
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const |
Find out whether this CRS is correctly initialised and usable
Get the units that the projection is in
- Returns
- QGis::UnitType that gives the units for the coordinate system
Overloaded != operator used to compare to CRS's. Returns opposite bool value to operator ==
Overloaded == operator used to compare to CRS's. Internally it will delegate to the equals method described below
long QgsCoordinateReferenceSystem::postgisSrid |
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const |
Get the postgis srid for this srs
- Returns
- long theSRID the Postgis spatial_ref_sys identifier for this srs (defaults to 0)
QString QgsCoordinateReferenceSystem::projectionAcronym |
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const |
Get the Projection Acronym
- Returns
- QString theProjectionAcronym The official proj4 acronym for the projection family
- Note
- A zero length string will be returned if the projectionAcronym is uninitialised
bool QgsCoordinateReferenceSystem::readXML |
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QDomNode & |
theNode | ) |
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Restores state from the given Dom node.
- Parameters
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theNode | The node from which state will be restored |
- Returns
- bool True on success, False on failure
bool QgsCoordinateReferenceSystem::saveAsUserCRS |
( |
QString |
name | ) |
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Copied from QgsCustomProjectionDialog /// Please refactor into SQL handler !!! ///.
Save the proj4-string as a custom CRS
- Returns
- bool true if success else false
Sets custom function to force valid CRS QGIS uses implementation in QgisGui::customSrsValidation.
- Note
- not available in python bindings
void QgsCoordinateReferenceSystem::setupESRIWktFix |
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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.
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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() .
void QgsCoordinateReferenceSystem::setValidationHint |
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QString |
html | ) |
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Set user hint for validation
long QgsCoordinateReferenceSystem::srsid |
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const |
Get the SrsId - if possible
- Returns
- long theSrsId The internal sqlite3 srs.db primary key for this srs
int QgsCoordinateReferenceSystem::syncDb |
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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.
QString QgsCoordinateReferenceSystem::toProj4 |
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const |
Get the Proj Proj4 string representation of this srs.
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
- QString theProj4String Proj4 format specifies that define this srs.
- Note
- A zero length string will be returned if the toProj4 is uninitialised
QString QgsCoordinateReferenceSystem::toWkt |
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const |
A helper to get an wkt representation of this srs
- Returns
- string containing Wkt of the srs
void QgsCoordinateReferenceSystem::validate |
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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 srs to be valid.
QString QgsCoordinateReferenceSystem::validationHint |
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Get user hint for validation
bool QgsCoordinateReferenceSystem::writeXML |
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QDomNode & |
theNode, |
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QDomDocument & |
theDoc |
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) |
| 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>
<srid>4326</srid>
<epsg>4326</epsg>
<projectionacronym>longlat</projectionacronym>
<ellipsoidacronym>WGS84</ellipsoidacronym>
</spatialrefsys>
- Parameters
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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
The documentation for this class was generated from the following files: