Linked from
The 9 pages that link to Great Trigonometrical Survey, each with the reason it gives.
HimalayasRelated: Its triangulation produced the first accurate elevation of Everest, then Peak XV.
Eight-thousandersRelated: Its measurements established the elevations of several Himalayan giants.
George EverestBroader topic: It was the central undertaking Everest directed as Surveyor General.
Radhanath SikdarNarrower topic: Sikdar’s calculations formed part of this vast surveying project.