Dear all, I am a brazilian cave topographer and I am developing a methodology of planimetric trilateration for magnetic influenced caves (Brazil has thousands of caves in iron formation rocks). These surveys only use tape and clinometer, surveying triangles, starting from two coordinates known stations. I have been able to calculate coordinates for all the stations and predict specific cartesian standard deviations for each leg, and prepared both normal and cartesian output that can be read by Therion (I suppose that by Survex too, although I am not a Survex user). Is there a way to specify specific standard deviations for each leg in Therion? I understood that the SD command is only for surveys, isn´t it? Because of trilateration a complex triangle network is created in this kind of survey and it will be very useful to close them in a least Squares algorithm, such as Therion´s. I am sorry if this is a too basic question, but I got stuck in this. Regards, Marcelo Taylor Cel: +55 21 9 9344 5196 marcelo.taylor@gmail.com