The well-known problem that the observed strike of a shallow-dipping rock f
racture can vary widely, even if one re-measures the strike in the same loc
ation, is dealt with in this paper. The overall purpose of the paper is to
place the statistical estimation of the strike confidence interval for shal
low-dipping rock fracture sets on a sound foundation. We have made series o
f strike measurements at each of various dips on a wooden laboratory "fract
ure" to allow estimation of strike standard deviation at all shallow dips.
This is accurate for smooth rock and serves as a lower bound estimate for r
ock with a rougher surface. These estimates are used, along with two indepe
ndent iterative statistical procedures, to reestimate the dip direction con
fidence interval of an actual set of nineteen fractures. The dip direction
confidence interval is more than three times as wide as the corresponding d
ip confidence interval. This will be made visible in our transformed confid
ence region plot for the mean pole.