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In order to mitigate position jumps when switching between fixed and float modes the rover can be set to remain in
float mode selected using the message UBX-CFG-DGNSS. In this mode, the Rover will estimate the ambiguities as
float but will not attempt to fix them.
The firmware requires a minimum of five ambiguities to attempt fixing. RTK fixed status can be reached when
either 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 Rover
The 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 only
RTCM3 for protocol in.
Figure 8: Configuring Rover radio link
4.2.8 Navigation rates supported with standard RTK
The following navigation rate constraints are advised when using the C94 boards for RTCM correction messages
using 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 the
Base must remain at a default of 1 Hz. The update rate of the RTCM3 messages sent from the Base should
remain at 1 Hz and will not affect the accuracy of the Rover. N.B This is not supported in moving baseline
operation.
4.3 Moving baseline RTK Configuration
A moving baseline (MB) configuration differs from standard RTK in that the base station is not necessarily stationary
and can move relative to the rover receiver. The rover position solution provides the user with a vector describing
the difference between the base and rover locations. This is a useful solution for providing a vehicle attitude or
angular 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. Note
that the maximum achievable update rates are only possible with a wired connection compared to the radio
modem. A wired connection is a good solution for co-located Base and Rover devices.
4.3.1 Base station operation
When the NEO-M8P functions as a Base Station, the receiver uses measurements from all available satellites to
broadcast corrections. The Base Station is configured for MB operation by enabling the RTCM message 4072 and
sending the CFG-TMODE3 message with 'Mode' disabled.
Disabling the fixed mode in CFG-TMODE3 is required to activate the moving baseline feature even if Message
4072 is enabled.
UBX-15031066 - R07
Early Production Information
C94-M8P - User Guide
Configuration
Page 17 of 47
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