[surveying] In surveying, an alphanumeric or numeric value included in an instrument vendor’s data collector file format. Operation codes are used to describe such elements as new instrument setups and numeric values for horizontal angles, zenith angles, slope distance measurements, height of instrument, and height of target. These basic operation codes are supported in Survey Analyst for field measurements for the following formats: Geoserial Interface (GSI), TDS raw, TDS coordinate, Geodimeter, and Sokkia SDR.