19.2.5 Error Propagation

The core equation for the propagation of the errors from the error source through to the survey position error is:

Wellbore positions are calculated using one of the standard methods such as minimum curvature or balanced
tangential, so over an interval, the dr/dp matrix depends on the surveys at either end of the interval.

The tool model for any particular survey instrument will usually include a number of different error sources, and we must consider all survey legs in the well and all the survey stations in each leg. So for a well we must add the error contributions over all survey legs in the well; each survey station in each leg and the contributions from each error source.