19.3.3 MWD Weighting Functions

As described in the example in section 19.2.4 the MWD weighting functions are determined by taking the partial derivatives of the survey equations with respect to the error sources. All of the MWD weighting functions are detailed in Appendix B.

Even a quick glance shows that many of the weighting functions are zero. Of the total list of error sources, only the four depth terms have any influence on measured depth. Some of the functions such as the effect of the declination errors on azimuth or sag error on inclination are relatively simple equations. However, other sources such as the accelerometer error sources may influence both the inclination and azimuth measurements and, particularly in the azimuth case, lead to relatively complex equations to be evaluated at each survey station.