Enough to determine the orientation of defects and seams "by eye". Take your smartphone and apply the bottom edge along the normal to the pipe. It is especially convenient if the smartphone has symmetrical protrusions on the lower edge. On the screen, you will see a value that is much more accurate than the "eye" measurement.
This application allows you to calculate the volume, length and mass of a pipe, as well as to determine the orientation of defects along a circle in dimensions: Degrees, Hours or Hours: Minutes.
The measurement accuracy directly depends on the accelerometer and gyroscope of the smartphone.