Snow gauge telemetry works by throwing a signal from a tower down to the ground. It measures the time it takes the signal to hit the surface and reflect back up to the receiver. It does this every hour. The delta you are referencing is the change in that surface elevation between two selected points in time. This is different than cumulative snowfall that ski resorts are publishing. The delta is not only effected by cumulative snowfall but also by compaction of the snowpack, evaporation, and ground infiltration. This is by design, it take into account density and tracks the total amount of snow water equivalent which is a true measure of water supply which is what SNOTEL is for. Snowbird is measuring 27” of snow accumulation measured every 12 hours and added together. SNOTEL is reporting change (delta) in depth on the ground accounting for compaction.

The system is automated and pretty cut and dry. I’m not sure where or how you think the error is introduced. Occasionally a sensor gets out of whack and needs adjustment, but that’s the exception.

This gives a good explanation of SNOTEL and also how resorts calculate their accumulation, and even explains the discrepancy you’re seeing: