Bug report #9827

QGIS slows down dramatically if 'ask for datum transformation' dialog option is on

Added by Regis Haubourg over 10 years ago. Updated about 10 years ago.

Category:Projection Support
Affected QGIS version:2.2.0 Regression?:No
Operating System:windows / osgeo4w Easy fix?:No
Pull Request or Patch supplied:No Resolution:fixed/implemented
Crashes QGIS or corrupts data:No Copied to github as #:18358


Qgis slows down dramatically when opening projects with layers in differents projections, if that option is enabled.
Not showing the dialog does a good workaround the issue.
This is a real blocker, discovered on the first 2.2 release training day here. Every client was stucked sometimes for 20 minutes.. Really hard to diagnose indeed.
Would be really great to backport.

bug_qgis_22.png (74.2 KB) Regis Haubourg, 2014-03-20 08:26 AM


#1 Updated by Michael Douchin over 10 years ago


You mean when on-the-fly projection is enabled, and the project contains several layers with different CRS ?
In the workaround mentionned, which dialog are you talking of ?

#2 Updated by Regis Haubourg over 10 years ago

Salut Michael.
The mentionned dialog is in attached file. Problem remains if qgs file properties where saved with OTF Off.

#3 Updated by Marco Hugentobler over 10 years ago

  • Status changed from Open to Feedback

From the description, it is not clear to me what you mean by 'slowness'. Is it a) that the users had to make a choice for the datum transformation when opening projects saved with older versions (and click 'remember') or b) was the application also slower if all the datum transform information has been present?

#4 Updated by Regis Haubourg over 10 years ago

Well, after the first dialog warning for older qgs version, then, layers are loaded. First layers are loaded fast, until a layer requiring reprojection is hit. No datum dialog raise, but QGIS waits for sometimes 10 minutes on each layer after that..

I will check if list of datum reprojections set in general option has an effect..

#5 Updated by Martin Dobias about 10 years ago

Please test again if the problem persists in current master (there have been some changes in the implementation)

#6 Updated by Pedro Venâncio about 10 years ago

I can confirm this in QGIS 2.2, not only when opening a saved project, but also when adding two layers (it's more noticeable with heavy layers) with different datum. The datum transformation dialog box takes a long time to appear.

With QGIS master, everything seems to be resolved.

#7 Updated by Giovanni Manghi about 10 years ago

  • Resolution set to fixed/implemented
  • Status changed from Feedback to Closed

Please reopen if necessary.

Also available in: Atom PDF