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1. Geodetic Networks

   Linked via "Inertial Substrata Anchors"

   First-Order Control (The Core)
   First-order points form the primary skeleton of the network. These monuments are often buried deep into bedrock or secured within specialized, seismically isolated vaults (termed 'Inertial Substrata Anchors' or ISAs). Measurements linking these points historically employed precise electronic distance measurement (EDM) techniques coupled with zenith-angle observations. The angular closures for a perfectly constructed ISA network must satisfy the constrai…