Proficient in all types of surveying, including surface and underground mine surveying, construction surveying, boundary surveying, GPS surveying, oil and gas well location surveying, and specializing in expert witness testimony for boundary litigation, GPS survey design and analysis, and underground surveying and mapping.

Former Chapter Representative, Board of Examiner's Liaison, Member of the Board of Directors, West Virginia Representative to the NSPS Board of Governors, and President, of the West Virginia Association of Land Surveyors, between 1991 and 1999. Also served on the Legislative Committee, Peer Review Committee, HARN Committee, and Education Committee.

Member of the Advisory Board to the Glenville State College Division of Land Resources for the Land Surveying Program. He has been Chairman of that Board from 2005 to the present.

Former member of the NCEES (National Council of Examiners of Engineers and Surveyors) EPS (Examination for Professional Surveyors) Committee. This committee is responsible for preparing and evaluating the national Fundamentals of Land Surveying Examination and the Principles and Practice of Land Surveying Examination, both of which are administered to every candidate for licensure as a land surveyor in the fifty states. Marshall was active on this committee for 4 years, and served as Chairman of the Principles of Practice sub-committee for 2 years.

Marshall has presented numerous seminars on boundary law issues and boundary resolution, right-of-way and easement issues, GPS and GIS applications to the surveying profession, State Plane Coordinates, Project Datums, and underground surveying and mapping.

Former member of the West Virginia Board of Professional Surveyors, serving two three-year terms, from 2000 to 2006.