Spencer A. Buckner III, 78, a retired civil engineer and surveyor with the Corps of Engineers who was involved in construction of the Pentagon and other major projects in this area, died Dec. 5 at the Sleepy Hollow Manor nursing home in Annandale. He had Parkinson's disease.

Mr. Buckner, who was born in Loudon County, Va., graduated from the Virginia Polytechnic Institute in Blacksburg. During the 1920s he worked for the U.S. Coast and Geodetic Survey in the Midwest and New England, and the U.S. Geological Survey in Idaho and Arizona.

He moved to the Washington area in 1929 and went to work for the Corps of Engineers. He took part in the surveying and construction of National Airport, the Pentagon, Andrews Air Force Base, various Nike sites and the dredging of the Potomac and Rappahannock river channels. After his retirement from government service in 1961, Mr. Buckner maintained a private surveying practice.

Mr. Buckner was a member of the American Congress on Surveying and Mapping and the Virginia Association of Surveyors.

Survivors include his wife, Gertrude H. of Falls Church, two sons, Spencer A. IV of Dallas, and Grayson T. of San Clemente, Calif., and one granddaughter.

The family suggests that expressions of sympathy be in the form of contributions to the Parkinson's Disease Foundation, 640 W. 168th St., New York, N. Y. 10032.