Stelios Thinking laterally... What about using conventional tape compass and clino data input, but set the standard deviation for the compass so large that therion practically ignores the compass reading (ie almost all the loop closure adjustment happens in the compass readings). So my idea is; Give each intersection a station name You know the tape distances for each leg of each triangle. You know the clino is always zero. Adopt a bearing for the base leg. Guess a compass bearing, +-20 deg say, for each leg of each triangle (you already have a map so it must be approximately to scale). Each triangle is a loop, and with any luck therion will close the loops with minimal change in the length of each leg. Be interested to see what happens. Bruce