Frequently asked questions

XSDError: Loaded schema file is invalid error encountered when running DataExplorer

You may encounter the following error (or similar) on opening .gml, .cnd, std or .prj files in the Data Explorer or file conversion tools (e.g., OGSFileConverter):

Error message:

Error XSDError in, at line 1, column 1: Start tag expected.
Error XSDError in file:///../bc/well.cnd, at line 5, column 195: Loaded schema file is invalid.
XMLInterface::isValid() - XML File is invalid (in reference to schema ./OpenGeoSysCND.xsd).
Error XSDError in, at line 1, column 1: Start tag expected.


Open the affected file (e.g. well.cnd in this case) in a text editor and remove the following parameter of the XML root element (the first element in < >-brackets in the element, e.g. <OpenGeoSysCND>):


where XXX can be CND, GLI, PRJ or STN depending on the file type.

Now, save the modified file and try to load it again.

Background info: The XSD files may be downloaded from a web location. We changed the protocol of our web site to `https://` but due to some weird behavior of the Qt XML validation code it tries to download the file (even if it is available locally) and does not respect the URL redirection to `https://` of the web server. Simply removing the part solves the problem. The XML is still validated! Newer OGS versions do not write that parameter into files anymore, see [!2198](

Oh, no! It diverges

OpenGeoSys will sometimes crash with an error message stating, that it couldn’t reduce the time step any more. There are several things that can be done to solve this:

  • In Time loop adjust time stepping allowing smaller time steps to be taken.
  • In Time loop adjust the error tolerance
  • Check if mesh quality is sufficient
  • Verify if all parameters, especially those that vary during the simulation, make physical sense throughout the whole experiment and combined with other parameters.

Oh, no! There are NaNs everywhere

If in the output log all values are NaN and one or more parameters were defined as functions, there is a good chance that a division by zero, or other undefined operation happened.

This article was written by Lars Bilke and Feliks Kiszkurno. If you are missing something or you find an error please let us know.
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