6. Oriented drill cores

library(structr)

The function drillcore_orientation() calculates the orientation of a plane or line from internal core angles (alpha, beta, and gamma) of oriented drill cores.

azi is the azimuth of drill core axis orientation (in degrees, measured clockwise from North), and inc is the inclination of drill core axis (in degrees).

azi <- 225
inc <- -45

Note that egative values for the inclination indicate downward direction

alpha and beta are the internal core angles alpha and beta, respectively, measured in degrees.

drillcore_orientation(azi, inc, alpha = 60, beta = 320)
#>      dip_direction      dip
#> [1,]      25.00392 70.02959
#> attr(,"class")
#> [1] "plane"

The function returns a spherical objects. Since only alpha and beta angles are specified, the output is a "plane" object.

For several alpha and beta angles:

planes_AB <- drillcore_orientation(azi, inc, alpha = c(60, 45), beta = c(320, 220))

The orientations can be plotted in a equal area (lower hemisphere) projection:

# initialize stereonet:
stereoplot()

# plot the core axis *azi and inc angles)
stereo_point(Line(azi, -inc), lab = "core-axis")

# plot the plane orientations as poles...
stereo_point(planes_AB, lab = c("A", "B"), col = c("#B63679FF", "#FB8861FF"))

# ... and as great circles
stereo_greatcircle(planes_AB, col = c("#B63679FF", "#FB8861FF"))

Tobias Stephan

2025-08-08