Datasheet
Table Of Contents
- Document Information
- Contents
- 1 Functional description
- 1.1 Overview
- 1.2 Product features
- 1.3 Performance
- 1.4 Block diagram
- 1.5 Supported GNSS Constellations
- 1.6 Assisted GNSS (A-GNSS)
- 1.7 Augmentation Systems
- 1.8 Broadcast Navigation Data
- 1.9 Untethered Dead Reckoning (UDR)
- 1.10 Odometer
- 1.11 Data logging
- 1.12 Geofencing
- 1.13 Message Integrity Protection
- 1.14 Spoofing Detection
- 1.15 TIMEPULSE
- 1.16 Protocols and interfaces
- 1.17 Interfaces
- 1.18 Clock generation
- 1.19 Power management
- 1.20 Antenna
- 2 Pin Definition
- 3 Configuration management
- 4 Electrical specification
- 5 Mechanical specifications
- 6 Reliability tests and approvals
- 7 Product handling & soldering
- 8 Default messages
- 9 Labeling and ordering information
- Related documents
- Revision history
- Contact
NEO-M8U - Data Sheet
UBX-15015679 - R06 Functional description Page 10 of 27
Product Information
1.7.5 Differential GPS (D-GPS)
The use of Differential-GPS data improves GPS position accuracy using real time data from a nearby
reference receiver or network. The NEO-M8U receiver supports D-GPS only with Dead Reckoning
disabled (using message UBX-CFG-NAVX5). D-GPS starts on receipt of valid data according RTCM
10402.3: “RECOMMENDED STANDARDS FOR DIFFERENTIAL GNSS”. RTCM cannot be used
together with SBAS or Dead Reckoning and is applicable only to GPS signals in the NEO-M8U. The
RTCM implementation supports the following RTCM 2.3 messages:
Message Type Description
1 Differential GPS Corrections
2 Delta Differential GPS Corrections
3 GPS Reference Station Parameters
9 GPS Partial Correction Set
Table 3: Supported RTCM 2.3 messages
1.8 Broadcast Navigation Data
The NEO-M8U can output all the GNSS broadcast data upon reception from tracked satellites. This
includes all the supported GNSS signals plus the augmentation services SBAS, QZSS and IMES.
The L1- SAIF signal provided by QZSS can be enabled for reception via a GNSS configuration
message.
1.9 Untethered Dead Reckoning (UDR)
u-blox’s proprietary Untethered Dead Reckoning (UDR) solution uses an inertial measurement unit
(IMU) included within the module. IMU data and GNSS signals are processed together, achieving
accurate and continuous positioning in GNSS-hostile environments (e.g. urban canyons) and useful
positioning even in case of complete GNSS signal absence (e.g. tunnels and parking garages).
The NEO-M8U combines GNSS and IMU measurements and calculates position solutions at rates of
up to 2 Hz. These solutions are reported in standard NMEA, UBX-NAV-PVT and related messages. A
new High Navigation Rate output message (UBX-HNR-PVT) extends these results with IMU-only data
to deliver accurate, low latency position solutions at rates up to 30 Hz.
Dead reckoning allows navigation to commence as soon as power is applied to the module (i.e. before
a GNSS fix has been established) and given all of the following conditions:
• the vehicle has not been moved without power applied to the module
• at least a dead-reckoning fix was available when the vehicle was last used
• a back-up supply has been available for the module since the vehicle was last used
For post-processing applications sensor data is available from messages UBX-ESF-MEAS and UBX-
ESF-RAW (high rate). Each message includes the time of measurement.