What is Nautical Assessors?

Legal Definition
Experienced shipmasters, or other persons having special knowledge of navigatiou and nautical affairs, who are called to the assistance of a court of admiralty, in difficult cases involving questions of negligence, and who sit with the judge during the argument, and give their advice upon questions of seamanship or the weight of testimony. The Empire (D. C.) 19 Fed. 559; The Clement, 2 Curt. 369, Fed. Cas. No. 2,879.
-- Black's Law Dictionary
Legal Definition
Experts in navigation called in to aid an admiralty court.
-- Ballentine's Law Dictionary