ITEM C2 PLEASE IDENTIFY BENCHMARK: A field survey is required for items C2. Most control networks will assign a unique identifier for each benchmark. For example, the National Geodetic Survey uses the permanent Identifier (PID). For the benchmark utilized, provide the PID or other unique identifier assigned by the maintainer of the benchmark. For GPS survey, indicate the benchmark used for the base station, the continuously Operating Reference Stations (CORS) sites used for an On-line Positioning User Service (OPUS) solution (also attach the OPUS report), or the name of the Real Time Network used.