видимо, здесь речь идет о высоте от дна танка

Как-нибудь так.

--------------------------------------------------
Note added at 13 mins (2008-01-16 07:58:14 GMT)
--------------------------------------------------

предварительный домотр
предварительная проверка

--------------------------------------------------
Note added at 2 hrs (2008-01-16 10:18:38 GMT)
--------------------------------------------------

Раз в кавычках, то, как мне кажется, нужно искать ассоциации с обычным выражением first foot, что значит - первый гость (в новом году).

Определение:
A sample taken after approximately 1 ft.(0.3 m) of cargo has been loaded
Эти пробы берут именно при загрузке.
Есть еще и "second foot" samples

Sampling serves two purposes. In the case of high purity cargoes, inspection of samples drawn at the manifold, or at * first-foot* level in the cargo tanks, allows the crew to assess the quality of the incoming cargo as well as the cleanliness of the lines. Obviously analysis cannot be carried out on the samples immediately but visual inspection allows the observer to assess any change in colour, the presence of water (if water is not soluble in the cargo),the presence of foreign particulate matter and, less straightforward, odour taint. Odour is not an issue for all cargoes. Toxic or highly odoriferous cargoes should not be tested for odour.
http://www.britanniapandi.com/index3.html?/publications/risk...