[Therion] Joining old and new surveys

Hi, I have an old survey from the 80s and I have new sections that I want to add with Therion. The old survey has no centerline data. I have redrawn the old survey in a th2 file and allocated 3 points which correspond to 3 different entrances. In the th file I have given coordinates to all 3 of those points. This works perfectly. I am struggling to connect the new section with this old section. The new section starts in a deep section of the cave and is far away from any of my currently defined points. What is the easiest way to connect the new and old sections? Thanks, Steven