# Introduction

This module is used to measure fiducial marks that have been etched in the top of a FIB/SEM data cube, in order to get a measurement of how thick each slice was. [1] When preparing a site for FIB/SEM nanotomography, mill or deposit some sort of feature at a fixed angle on the top surface of the data volume. When viewed in cross-section, those features will get closer together the farther into the volume you mill. Utilizing the geometry of the situation, an estimate for the slice thickness can be obtained by comparing the distance between the two fiducials on subsequent slices.

It requires a PyQt and OpenCV installation in order to work, since a number of the methods are graphical and interactive. Installation of these can be a little tricky, but should be doable from the links given above.

[1] | https://www.google.com/patents/US8178838