GNSS Correction Module from u-blox Makes Way for Centimeter-level Positioning

January 23, 2020 by Gary Elinoff

u-blox claims that its NEO-D9S enhances GNSS data from satellite constellations to offer pin-point position readings.

The NEO-D9S from u-blox is a GNSS correction data receiver that garners global navigation satellite system (GNSS) correction data from correction service providers.

The unit then combines those corrections with the initial guidance from the satellite constellation. This information is collected by the “rovers” also mounted on the object being tracked.



u-blox’s NEO-D9S GNSS correction data receiver module. Image used courtesy of u-blox

The result is a position reading that is more accurate than what’s possible with the GNSS signals alone. 


What are GNSS Correction Services? 

GNSS correction services transmit data containing real-time information describing GNSS errors directly to GNSS correction data receivers. One such GNSS correction data receiver is the NEO-D9S.

The State Space Representation (SSR) is the newest iteration of GNSS correction service. It models the errors over large areas and transmits the data to the GNSS devices.

The rover combines the corrective data with the signals it has received directly from the GNSS to obtain extremely precise results.


State Space Representation

State Space Representation (SSR). Image (modified) used courtesy of u-blox


The SSR corrections are distributed over IP and L-Band (1525MHz to 1559MHz) satellite communication channels. These services allow centimeter-level positioning accuracy over large geographic areas.

Bandwidth requirements are low, and because all roving GNSS receivers rely on the same GNSS correction data stream, SSR services can be inexpensive enough for mass-market applications.


Basic Operations of GNSS Correction Module

The NEO-D9S contains a processor that decrypts the correction data from the GNSS correction service and provides it to a GNSS receiver, such as u-blox’s ZED-F9P module. 


GNSS architecture

The NEO-D9S works in conjunction with GNSS receivers, such as u-blox’s ZED-F9P.  Image (modified) used courtesy of u-blox


The unit is initially configured to work with whichever correction service has been set as default. It can also be configured for any other L-band data broadcast. Configuration settings are stored in non-volatile memory.

To ensure high RF sensitivity as well as resistance to interference from adjacent channels, the NEO-D9S incorporates a SAW filter and a TCXO.


Designed for Automotive OEMs

L-band connectivity will unshackle the NEO-D9S from the expense and unreliability of cellular connectivity.

As such, the device may be useful for automobile manufacturers and their Tier 1 OEMs. The unit will also serve device developers who need inexpensive but extremely accurate position information no matter where they travel—even on a continent-wide basis.


Security Features

The NEO-D9S incorporates anti-spoofing algorithms. It also includes a signature mechanism to ensure safe firmware updates. 

Anti-jamming capabilities include active CW detection and removal.


Physical Considerations

The device operates from a 1.65V to 3.6V power supply. At 3V, the average power consumption is 35mA.

Both the professional-grade NEO-D9S-00B and the automotive-grade NEO-DS9-00A operate over a temperature range of -40℃ to +85℃. They are also RoHS compliant (lead-free) and environmentally friendly (halogen-free). 

The units are available in 24-pin leadless chip carrier (LCC) packages sized at 12.2mm x 16.0mm x 2.4mm and weighing 1.6 grams.


Support Tools

u-blox offers the C101-D9S application board for the NEO-D9S. There is also an application board, the C100-F9K, targeted at the ZED-F9K.