Datamine Discover KB :: Calculation used for generating drillhole cross section

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Calculation used for generating drillhole cross section

Discover does not plot the raw survey data. Instead an interpolation method known as “mid-point tangential averaging”or “back calculation” is used. This is the only method offered in Discover and is the default method in Discover 3D. Although it is a simple method, it does produce reasonable results.
Each survey point is considered to lie in the middle of a drillhole segment which has the dip and azimuth of the survey location. The dip and azimuth of the hole changes automatically halfway between each survey point. This has the affect of intersecting a midpoint in between the actual survey points, and may not actually intersect a survey point. It also means that the first and last interval of the trace will be half their expected length.

If there is no survey measurement at the start (0 m depth), the first record's Azimuth and Dip values are used for the initial segment. Similarly, at the end of hole, the last measured azimuth/dip is continued for the final segments.

Put simply, if your collar is at 0 m and finishes at 40 m and you have down hole surveys at depth intervals of 10 m, 20 m and 30 m, then Discover will compute the the end X,Y,Z coordinate of the first line segment using the midpoint distance between each depth interval (e.g. 0 m to 5 m). It then uses corresponding dip and azimuth values from the surveys (10 m measurement), to project the second line segment (5 m to 15 m). At this point it then uses the next Survey dip and azimuth record (20 m) to generate the next segment.

If a record exist is in both the Collar and Survey tables for 0m, the Survey table data is used preferentially.

This has the effect of making “curved” holes more curved and a hole will diverge further from the “straight line” (called segments in Discover3D) location at increasing depth. If you have a high frequency of survey data (1 m intervals or less), then the effect of the interpolation will be negligible.