u-blox C94-M8P User Manual

Also see for C94-M8P: User guide

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C94-M8P - User GuideUBX-15031066 - R07 Early Production Information ConfigurationPage 17 of 47In order to mitigate position jumps when switching between fixed and float modes the rover can be set to remain infloat mode selected using the message UBX-CFG-DGNSS. In this mode, the Rover will estimate the ambiguities asfloat but will not attempt to fix them.The firmware requires a minimum of five ambiguities to attempt fixing. RTK fixed status can be reached wheneither of the following requirements is fulfilled: 1) six satellites from a single constellation are available, or 2)eight satellites from two different constellations are available.4.2.7 NEO-M8P UART settings for the RoverThe GNSS module UART needs to be configured on the Rover. Use UBX-CFG-PRT message to set “Protocol in” to“RTCM3” and “Protocol out” to “none”, as shown in Figure 8. Ensure "none" is selected for protocol out and onlyRTCM3 for protocol in.Figure 8: Configuring Rover radio link4.2.8 Navigation rates supported with standard RTKThe following navigation rate constraints are advised when using the C94 boards for RTCM correction messagesusing the C94 radio modems. A default of 1 Hz is recommended for the Base and Rover. The Rover can be configured for either 5 Hz (dual constellation) or 8 Hz (GPS only) maximum rates but theBase must remain at a default of 1 Hz. The update rate of the RTCM3 messages sent from the Base shouldremain at 1 Hz and will not affect the accuracy of the Rover. N.B This is not supported in moving baselineoperation.4.3 Moving baseline RTK ConfigurationA moving baseline (MB) configuration differs from standard RTK in that the base station is not necessarily stationaryand can move relative to the rover receiver. The rover position solution provides the user with a vector describingthe difference between the base and rover locations. This is a useful solution for providing a vehicle attitude orangular bearing when the receivers are co-located. This section covers the C94 configuration for MB operation.Either a wired or the wireless (radio modem) data connection is possible between the base and rover receivers. Notethat the maximum achievable update rates are only possible with a wired connection compared to the radiomodem. A wired connection is a good solution for co-located Base and Rover devices.4.3.1 Base station operationWhen the NEO-M8P functions as a Base Station, the receiver uses measurements from all available satellites tobroadcast corrections. The Base Station is configured for MB operation by enabling the RTCM message 4072 andsending the CFG-TMODE3 message with 'Mode' disabled.Disabling the fixed mode in CFG-TMODE3 is required to activate the moving baseline feature even if Message4072 is enabled.