Test Results of First-Order Class III Leveling.

摘要

The National Geodetic Survey has programmed for a partial releveling of the first-order,National vertical control net and for readjustment of the entire first-and second-order net during 1977through 1985. In the past,first-order,class I or II,double-run leveling was used exclusively to establish and relevel the first-order net. Programmed funds permit releveling and replacing destroyed marks on approximately half of the National first-order net by double-run leveling,or on essentially the entire net by new first-order,class III,single-run leveling. The new specifications,based on an analysis of leveling errors,were field-tested on a level line from Waldorf to Baltimore,Md. between December 1975and April 1976. Test results indicate that first-order,class III leveling can provide a viable alternative to first-order,Class I leveling for releveling the first-order,National vertical control net.