How is the trajectory of a hole calculated?

In most cases a drillhole describes a curved trajectory (known as a trace). When you construct or modify a Drillhole Database, the application mathematically renders each hole by linking successive downhole surveys with a series of 3D spherical arcs.

These arcs are calculated by linearly interpolating azimuth and inclination between successive downhole surveys.

However, to simplify the trace display, the application approximates those arcs with a series of straight-line segments, and automatically varies the length of each straight-line segment (the trace interval) on a hole-by-hole basis, always keeping the displayed trace location within 5 cm of the mathematical location.

Consequently, straight holes are always depicted with two points – one at the collar, and another at the end of hole. Curved holes, however, are given a trace interval that varies according to the curvature of the hole; the more curved the hole, the shorter the trace interval and the more points required to draw it.

If the deepest survey point is not at the end of the hole, the last inclination and azimuth survey in the Survey file is used from the point of the last survey to the end of the hole.