Directional Magnetic Multi shot Survey Tool Instrument
At certain points in the well it is useful to determine the overall trajectory (Check directional survey calculations excel sheet) in a single survey run (e.g. just before running casing). This is usually done by a Directional Magnetic Multi shot Survey Tool Instrument which takes a series of pictures. (can be dropped from surface or run on W/L).
https://www.drillingmanual.com/2017/12/directional-magnetic-multi-shot-survey-tool.html