I received an email from the USGS QC team indicating that the System Identifier (SystemID) field in the LAS header quite often is something other than the sensor used to collect the data. The spec is deliberately vague on its actual implementation, and in my opinion that's a good thing.

I believe it's clear how to implement it for a file containing a single flightline, but it's unclear how this field can be best utilized if data from multiple sensors are in the LAS file. For example, 32 characters is barely enough for something simple like "Leica ALS80 & Riegl 1560i" but if serial numbers are desired it gets too long.

Does anyone have experience with a good multi-sensor implementation they're happy with that we can recommend? I'm not sure that this merits a change to the specification, but we can perhaps provide guidance to USGS for their contractors.
@jstoker74