Data Sheet

NEO-M8P - Data Sheet
UBX-15016656 - R06 Early Production Information Functional description
Page 10 of 30
Figure 3 Estimated angular error for fixed base-line with a typical 1 sigma (0.08 cm) relative position error
1.6.3 RTCM message requirements
In static mode, it is critical that the RTCM observation messages (e.g. RTCM 1077 and RTCM 1087, or RTCM
1077 and RTCM 1127) be generated from the same navigation epoch. This might not be the case when the
messages are enabled individually at a lower rate than the navigation rate. For this reason, the user should
configure the navigation rate of the reference station to be the same as the desired RTCM observation message
rate. For this mode, the RTCM standard recommends using 1 Hz.
In moving baseline mode, it is critical that the Base sends the position (i.e. RTCM 4072) and observation (i.e.
RTCM 1077 and RTCM 1087, or RTCM 1077 and RTCM 1127) messages at the same rate as its navigation rate.
Additionally, to ensure optimal performance the Base and Rover receiver should use the same navigation rate.
To ensure GLONASS ambiguity fixing, the reference station must be configured to output RTCM message 1230.
This message can be sent at a rate lower than the observation messages as the bias values will be held until a
new version of the message is received.
The communication link from the Base to the Rover must be reliable. Breaks in this communication will result in
the Rover solution degrading, and eventually falling back to an independent navigation fix, dependent on
configuration setting. The RTCM messages output from the Base are by default configured to the recommended
1 Hz output rate. Corrections from a static Base for GPS/GLONASS (or GPS/BeiDou) at this navigation rate will
amount to a load of approximately 500 bytes/s, assuming an update rate of 1Hz using MSM7 corrections for 20
GPS/GLONASS (or GPS/BeiDou) satellites.
To reduce the load in static mode it is possible to use MSM4 instead of MSM7 messages. In this case, the
load will reduce to approximately 300 bytes/s.
For a Base operating at 4 Hz in moving baseline mode, assuming 20 GPS/GLONASS (or GPS/BeiDou) satellites,
the load will increase to approximately 2 kbytes/s.
In moving baseline mode, it is not possible to use MSM4 messages.
When the module receives a valid stream of RTCM 3 messages, the RTK_STAT status pin is set into an
alternating, blinking mode. The RTK_STAT status pin is set active low when the Rover module is operating in
RTK Fixed mode. The message UBX-RXM-RTCM will echo basic information about received RTCM input
messages and can be used to monitor the quality of the communication link.
For more details see the u-blox 8 / u-blox M8 Receiver Description Including Protocol Specification [2].
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Estimated Angle error (deg.)
Baseline length (m)
Angle Error vs Baseline length (m)