The main conceptual difference between dual beam, dual constellation and dual frequency is dual beam refers to VERIPOS correction data from L-Band beams with dual constellation and dual frequency referring to GNSS. Dual constellation is relating to satellites being used and dual frequency is the band of signal from the satellite.
The term dual beam is where there are 2 (or more) VERIPOS units on board a single vessel that are locked onto 2 different L-Band beams, thus giving dual beam redundancy. For example if working in the North Sea 1 unit could be locked to AORE and the other locked to 25E.
Dual frequency refers to the frequency bands output from the GNSS satellites. Satellites currently can output within 2 frequency bands, they are known as either L1 or L2. L1 is the minimum frequency band required for VERIPOS services, if using a PPP service either Apex or Ultra they will require L1 and L2 with this being dual frequency. All VERIPOS supplied receivers have permissions for L1 GPS frequency, to gain L2 a new permission file may be required to upgrade the GNSS receiver allowing decoding of the L2 GNSS data.
There are currently 2 different constellations VERIPOS equipment can use to generate a position, these being GPS and Glonass. When GPS and Glonass are used together to provide a position this is known as dual constellation. VERIPOS currently offer 3 single constellation options Standard, Apex and Ultra, these services are known as single constellation due to using only GPS satellites. VERIPOS also offer a further 3 services Standard², Apex² and Ultra², these services use GPS and Glonass satellites and are known dual constellation.