I have a few files that are fake data made from paper surveys. These come in various formats but a common one, and the one I tend to make if I do it is in the form of data cartesian station easting northing altitude It appears that Therion applies automatic declination by date to this form of data, so it defaulting to cartesian magnetic This is not the same default as Survex "By default, the North used is True North, but you can specify to use Magnetic or Grid North (in the input coordinate system) with the *cartesian command, and also specify an additional rotation to apply " The cartesian command does not seem to work in Therion. For now I've bodged it buy applying declination 0 degrees but it would be better if Therion followed the Survex manual to which the Therion book refers to for commands. An example file is http://www.cave-registry.org.uk/svn/CheddarCatchment/Longwood/Renolds/Renold... You will need revision 479, otherwise you will get the bodge fix thanks Andrew