A megalite survey or mechanical survey was an operation that could be performed on a Starfleet computer in the 23rd century for the purpose of detecting any defects or malfunctions.
In the 2267 court martial of Captain Kirk, it was revealed that the computer log recorded that Kirk prematurely jettisoned the Enterprise's ion pod, causing the death of Lieutenant Commander Benjamin Finney. Lieutenant Commander Spock then performed a megalite survey on the USS Enterprise's computer in an effort to discern if the computer could have been relaying false testimony, finding no evidence to support that claim. (TOS: "Court Martial")