Clearpath tends to supply the NovAtel SMART-6 when clients need such accuracy. It'll go down to 2 cm if the right upgrade options are selected, a base station is available, and everything's configured properly (warning: Don't underestimate the configuration time). It works with the standard navsat driver as well.
Originally posted by Ryan with karma: 3248 on 2014-12-10
This answer was ACCEPTED on the original site
Post score: 3
Original comments
Comment by T00Tall on 2014-12-10:
Thank you for you're answer. Do you happen to know of any database of nmea compatible devices? To top off my request I forgot to mention we need the device to be relatively small.
Comment by Ryan on 2014-12-11:
I can't think of any database, no. AFAIK, GPS devices which can't be configured for NMEA output are rare.