The Therion book p20 has this data <style> <readings order> ◃ set data style (normal, topofil, diving, cartesian, cylpolar, dimensions, nosurvey) and readings order. Reading is one of the following keywords: station, from, to, tape/length, [back]compass/[back]bearing, [back]clino/ [back]gradient, depth, fromdepth, todepth, depthchange, counter, fromcount, tocount, northing, easting, altitude, up/ceiling4, down/floor, left, right, ignore, ignoreall. See Survex manual for details. So trying this (from the survex manual v1.0.39) data nosurvey from to 1 3 As found in the 2 sample files (the actual connection would require a large dataset to be sent) The survex one produces a triangle, as I would expect the therion file gives the error unsurveyed shot between unfixed stations (adding a fix for station 1 and 3 gives the same error) So this is acting differently from survex, or possibly does not work at all (or I just have got it wrong again!) thanks Andrew PS expect an email on passage dimensions in centrelines, as that is really what I am working on, this was a little diversion