Holds the design model and control data, computes coordinates from instrument readings, guides setting out with live position feedback, records observations with their metadata, and exports the result. On a robotic total station it also controls the instrument remotely, which is what allows one-person operation.

The software, by a wide margin. Field capability - stakeout, resection, traverse closure, as-built comparison, volumes, and the file formats it reads and writes - determines what work you can do. Rugged hardware matters for survival, but a tough device running limited software still cannot do the job.

Because every conversion is an opportunity to lose or misapply a coordinate system, and those errors are silent. A collector that reads the design team's native formats directly removes that risk. Confirm compatibility against the formats actually used on your projects rather than a general claim of support.

An onboard collector on the instrument suits straightforward manual total station work. Robotic operation requires a separate controller, since the surveyor is at the pole rather than at the instrument, and GNSS work needs one as the interface to receiver and corrections.

Screen readability in direct sunlight above all - it is the most common complaint and the hardest to work around. Then ingress and drop rating, a battery that lasts a full day or can be hot-swapped, and connectivity for correction services and data transfer.

On modern systems yes, over mobile or cloud sync, so measured data reaches the office the same day and revised designs reach the field without a site visit. This removes the delay and the version confusion that arise when files are carried on removable media.

Traverse closure, resection residuals and check shots to known points are the important ones, since they reveal a bad setup before the error propagates through a day's work. Software that reports these clearly, rather than accepting any observation silently, is a genuine quality control.