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On proj6 builds, never apply a lossy conversion from WKT to proj strings

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when attempting to identify a CRS specified via WKT

Because:
1. Proj string conversion is lossy, so we will end up with misleading results
2. If proj can't identify the CRS based on the WKT alone, then any CRS it
identifies from a lossy proj conversion will be incorrect
3. Proj is smarter than QGIS, we should trust it and not rely on downstream hacks

(4. I want to implement creation of user CRS via WKT instead of only proj, and
having this hack in place will break things)
This commit is contained in:
Nyall Dawson 2019-11-29 08:43:17 +10:00
parent 3f94d55384
commit a99d94e5aa
1 changed files with 6 additions and 23 deletions
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29
src/core/qgscoordinatereferencesystem.cpp
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@ -784,12 +784,13 @@ bool QgsCoordinateReferenceSystem::createFromWkt( const QString &wkt )
#if PROJ_VERSION_MAJOR>=6
if ( d->mPj )
{
// try 1 - maybe we can directly grab the auth name and code from the crs already?
QString authName( proj_get_id_auth_name( d->mPj.get(), 0 ) );
QString authCode( proj_get_id_code( d->mPj.get(), 0 ) );
if ( authName.isEmpty() || authCode.isEmpty() )
{
// try 2, use proj's identify method and see if there's a nice (singular) candidate we can use
// try 2, use proj's identify method and see if there's a nice candidate we can use
QgsProjUtils::identifyCrs( d->mPj.get(), authName, authCode );
}
@ -818,29 +819,11 @@ bool QgsCoordinateReferenceSystem::createFromWkt( const QString &wkt )
}
#endif
// always morph from esri as it doesn't hurt anything
// FW: Hey, that's not right! It can screw stuff up! Disable
//myOgrSpatialRef.morphFromESRI();
// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
// WARNING - wkt to proj conversion is lossy, hence we DON'T DO THIS on proj 6
// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
// WARNING - wkt to proj conversion is lossy -- we should reevaluate all this logic!!
// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
#if PROJ_VERSION_MAJOR>=6
// create the proj4 structs needed for transforming
if ( d->mPj )
{
const QString proj4String = getFullProjString( d->mPj.get() );
if ( !proj4String.isEmpty() )
{
//now that we have the proj4string, delegate to createFromProj4 so
// that we can try to fill in the remaining class members...
//create from Proj will set the isValidFlag
createFromProj4( proj4String );
}
}
#else
#if PROJ_VERSION_MAJOR<6
// create the proj4 structs needed for transforming
char *proj4src = nullptr;
OSRExportToProj4( d->mCRS, &proj4src );