Verify the condition of the sounding tape and be aware of any deliberate altering of sounding tapes and using the wrong size of bobs.
Always use own sounding tape and a ruler to report exact sounding or ullage especially if it is below the 20 cm mark.
Note down the reference heights / gauge heights of each tank in a note book and check the same against reference height noted by physical measurement of the tanks.
The reference heights will differ if some foul play is involved like blocking the bottom of the sounding pipes with bobs later to be fished out.
In cases like these investigate further and take the entire missing length as "full sounding."
Pay particular attention to 'millimetre' soundings especially when the tanks are full and taking ullages as small errors will have a big impact of the total bunker quantity.
Kaivan H. Chinoy is the Founder and Principal Marine Surveyor of AVA Marine Group, owners of Petro
Inspect and The Bunker Detectives.