丈量員的主要職責是(a)協助測量主任(工程)及土地測量師職系人員進行實地測量工作；(b)就實地測量工作負責預備、看管、保養、運送及簡單維修測量設備、工具和物料；(c)保持擺放測量器材的儲存間整齊清潔；(d)利用小型測量設備／工具執行實地測量工作；以及(e)督導及協助訓練一級工人及二級工人。(註：丈量員或須不定時工作，以及在本港任何地區工作，包括多山及地面崎嶇不平的地區。)

A Chainman is mainly deployed on (a) assisting members of the Survey Officer (Engineering) and Land Surveyor grades to carry out surveying work in the field; (b) undertaking the preparation, care, transportation and simple maintenance of survey equipment, tools and materials for field survey operations; (c) maintaining the order and cleanliness of the survey stores; (d) using minor survey equipment/tools for execution of surveying tasks in the fields; and (e) supervising Workmen I and Workmen II as required and assisting in the training of Workmen I and Workmen II. (Note: A Chainman may be required to work irregular hours and work in any part of the territory including hilly and rugged area.)