The fixed points and the surface image are aligned almost perfectly, but the grid appears to be about 10m too far north >relative to the fixed points and surface image.
Correction: Referring to my original post, on creating a 'caves' text output (attached) I see that in fact the output grid is plotted correctly, but the fixed points and surface image have been input 0.6m too far east and 7.5 to 7.7m too far south relative to their explicitly stated input co-ordinates. So it would seem that it might in part be a Therion error in parsing/converting input co-ordinates rather than an output error? The north arrow still points south, unless I specify a DIFFERENT output co-ord system in the thconfig file; then it points north!?! Bruce