Hello everyone - I am struggling with a couple of survey shots that Therion is not interpretting correctly. It might be a bug in how Therion averages forward and backward compass when the readings are near 360 and 180 degrees. Here is a block of centerline data. The two shots causing problems are B8-B9 and B14-B15. data normal from to tape compass clino backcompass backclino left right up down B1 B2 35.7 32 22 214 -20 14 4 4 2.5 B2 B3 16.4 31 -20 211 21 9 - 12 3 B3 B4 40.5 18 3 197 -2 0 8 5 4 B4 B5 24.6 82 5 263 -5 4 8 40 4 B5 B6 18.8 18 -5 199 5 3 12 5 2 B6 B7 43.0 59.5 2 241 -2 - 10 0 2.5 B7 B8 67.7 348 0 169 0 6 3 2.5 4 B8 B9 28.5 359 -2 181 2 8 4 .5 1.5 <<=== B9 B10 25.2 351.5 1 174 -2 2 8 2 1 B10 B11 16.1 40 -3 221 3 4 7 0 1 B11 B12 38.0 0 2 180 -3 3 7 1.5 3 B12 B13 17.3 338 -6 160 5 10 10 2 1.5 B13 B14 28.0 338 3 158 -4 9 8 0 3.5 B14 B15 49.0 359.5 -1 180 0 7 4.5 0 5.5 <<=== B15 B16 46.3 7 -10 189 9 4.5 5 6 1.5 B16 B17 22.1 317.5 8 140 -8 8 7 3 4 B17 BM1 15.5 348.5 -5 168.5 4 4 10 15 4 As you can see, this passage is going basically straight north. Therion interprets both shots as having a forward compass reading of 180, with result that the compiled map has the passage going backward on itself. If I replace the back compass with a dash, then the map compiles correctly. I tried reversing the forward and backward compass readings, but it made no difference. One of the shots (B11-B12) has compass readings of exactly 0 and 180. This shot displays correctly on the map. Any thoughts? Thanks - Bill Gee