19.5.4 Poorly Defined Functions

The MWD model includes a set of equations for the cases where the weighting functions are mathematically illdefined in vertical hole. The situation at 90 inclinations, 90 (or 270) azimuth is physically ill defined and a software implementation must handle these.

The following weighting functions are ill-defined in vertical hole:
ABX, ABIX, ABY,ABIY, MX,MY, XYM3, XYM4, ABXY-TI2 and ABIXY-TI2
References [1] and [5] include alternative calculation options that can be used to evaluate these functions.