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PointPerfect L-band Configuration

Andrew Mercer
Updated

Introduction

PointPerfect L-band is a correction service delivered through an L-band satellite.  This delivery is ideal for use in remote and rural areas where cellular data services are unavailable, including offshore areas up to 12 nautical miles (roughly 22 kilometers) off coastlines.   

This guide will review the hardware requirements and device configuration to receive and use the PointPerfect service via L-band.  Instructions on configuring NEO-D9S and F9 receivers for this purpose are explained below. 

Note:  PointPerfect L-Band Satellite distribution is intended for customers in enterprise environments or those with B2B (business-to-business) agreements, and access may be provided when requested from an appropriate commercial domain account. At u-blox's discretion, exceptions may be made when the intended use is for academic purposes. Please email services-support@u-blox.com to request PointPerfect L-band access.

Benefits of PointPerfect L-band Corrections Distribution

PointPerfect L-band provides corrections offline without the need for a continuous internet connection.

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Do's & Don'ts: Best Practices and Common Pitfalls 

Do's: 

Don'ts: 

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Architecture

With our L-band service, encrypted continental SPARTN PointPerfect corrections are provided by a geostationary L-band satellite positioned above the equator. The corrections are delivered to a NEO-D9S receiver. The NEO-D9S receiver then passes the data to a high-precision receiver, such as the ZED-F9P.

More information about the L-band Dynamic Keys and Decryption is provided in later sections in this document. 

Hardware Requirements and Prerequisites 

To use the PointPerfect L-band solution, you need two receivers:

The correction receiver (NEO-D9S) receives encrypted PointPerfect L-band corrections from the L-band satellite and passes them to the F9 receiver.  The decryption of SPARTN messages happens within the F9 module using the current L-band dynamic keys.  

If you have not acquired the hardware to use L-band corrections, you can get started with both NEO-D9S and F9 receivers such as: 

The NEO-D9S and F9 receivers can be connected via UART2, which is common practice and recommended for customer designs. (See jumper configuration example in C101-D9S user guide.)  UART1 or USB are the most convenient interfaces for monitoring and configuring both modules (i.e. when using u-center etc.)

The NEO-D9S receiver requires an antenna that supports frequencies between 1540 MHz - 1559 MHz.  Please refer to section 4.2 of the NEO-D9S Integration manual [6] to learn more about antenna requirements. 

Along with the appropriate hardware devices mentioned above, PointPerfect L-band plans must be enabled on your thingstream domain to use the service. If you cannot select our PointPerfect L-band plans within your PointPerfect Location thing, please contact services-support@u-blox.com. 

L-band Receiver Configuration

The sections below describe how each receiver is configured. 

NEO-D9S configuration

NEO-D9S must be configured to receive SPARTN L-band correction data and forward these, encapsulated in UBX-RXM-PMP messages, to the F9 receiver via UART2.

L-band Configuration (D9S)

PointPerfect service-specific configuration for CFG-PMP keys (Point to multipoint configuration) must be implemented for your corresponding region on the NEO-D9S receiver before it can receive PointPerfect correction data. 

Please contact us at services-support@u-blox.com to obtain the NEO-D9S PointPerfect L-band HEX (a decimal) configuration string of these keys for your specific region.

The HEX string can be loaded by:

u-center-HEX.png

Interface Configuration (D9S)

The UART2 interface of NEO-D9S needs to be configured to allow communication with the F9 receiver, using the following configuration items.  In u-center, use View -> Generation 9 Configuration View -> Advanced Configuration View.

Configuration item Value

Also, confirm the CFG-MSGOUT-UBX_RXM_PMP_UART2 is set to 1 (by default is enabled).
This message enables UART2 of NEO-D9S to output UBX-RXM-PMP messages. 

Note:  The baud rate of 38400 is stated because it is the default setting for an F9 device.  You can make this higher, but make sure both devices (D9S and F9) have the same baud rate setting.

Functional Check (D9S)

Verify that NEO-D9S is operating correctly with these functional checks, most can be performed with u-center, see the Pointperfect Getting Started Guide for how to download it, and the u-center user guide for more information.

u-center-COMS.png

u-center-Packets.png

The UBX-RXM-PMP message can be used to check the decoded correction data (the image below is for reference only)

u-center-VER.png

u-center-PMP.png

It is important to check the UART2 communication to the F9.  In u-center, go to View, Messages View and find the UBX-MON-TXBUF message as shown in the image below.

u-center-TXBUF.png

F9 Receiver Configuration

Please confirm via the UBX-MON-VER message that the F9P has the latest firmware version.  

To use our L-Band service, the F9P device must be configured to receive and use the SPARTN L-band correction stream from the NEO-D9S in the form of a UBX-RXM-PMP message. 

 

L-band Configuration (F9)

The CFG-SPARTN-USE_SOURCE configuration key needs be set to LBAND:

Configuration item Value

This message value can be set using the View -> Generation 9 Configuration View -> Advanced Configuration View in u-center, please see the image below.

For more details regarding SPARTN source configuration, please refer to your product’s integration manual. 

u-center-GEN9.png

Interface Configuration (F9)

The UBX protocol needs to be enabled on the ZED-F9P UART2 input (via View -> Generation 9 Configuration View -> Advanced Configuration View):

Configuration item Value

L-band Dynamic Keys and Decryption

SPARTN corrections are decrypted within the F9 module itself.  The following article explains the L-band dynamic keys and how to collect and transfer them to the F9 receiver in UBX format; Managing SPARTN Dynamic Keys for PointPerfect L-Band Corrections . The F9 will then use the keys to decrypt the SPARTN corrections.  Please contact services-support@u-blox.com if you need help with getting the L-band keys to the F9 receiver.

Reminder: The keys are not stored in non-volatile memory and will be deleted on every module reset or restart. In such cases, the keys need to be passed to the F9 again. 

Functional Check (F9)

Functional checks that are required to verify the F9 module is operating correctly with NEO-D9S:

u-center-SPARTN.png

u-center-MON-COMMS.png

u-center-RXM-COR.png

If all these checks pass, the ZED-F9P receiver should get into RTK positioning fix. If you are not able to see any of the messages above, please contact services-support@u-blox.com for assistance.

u-center-TTFF.png

Maintaining Fix in degraded locations

It is IMPORTANT to NOTE there may be circumstances that cause your device to lose its corrections and fall back to 3D/DGNSS. This could be due to an interrupted L-Band connection - for example when driving under trees.  

To delay the fallback to DGNSS we recommend increasing the CFG-NAVSPG-CONSTR_DGNSSTO timeout value, please see the following article for further information: My Rover loses RTK Fix & goes into 3D/GNSS

Increasing the timeout value will need to be managed against how important it is for your use case to drop to DGNSS faster.  The accuracy degrades by a few Centimetre per minute, so setting the timeout to the maximum value of 255 seconds (approximately 4 minutes) will mean a reduced accuracy of approximately 10-20 CM. 

Determining your rover's line of sight to the PointPerfect L-Band satellite

See this guide: D9S Signal Troubleshooting with PointPerfect L-Band Pro tip #5

Understanding Age of Corrections in PointPerfect L-band Delivery

For customers accustomed to IP-based correction services, where correction ages are typically around 1-5 seconds, the 30-second correction age seen with L-band delivery may raise concerns. However, this is a normal characteristic of L-band transmission, which involves more transmission paths and higher latency compared to the faster IP method. In open-sky environments, an average correction age of 30 seconds is expected and does not affect performance. PointPerfect's hybrid PPP-RTK service is designed to operate reliably with these higher correction ages, maintaining precision and accuracy. As long as corrections remain under 60 seconds, the service functions as intended; beyond this threshold, the F9 module will revert to 3D/DGNSS to ensure reliable positioning data.

Still need help?

If you need more help or have any questions, please send an email to services-support@u-blox.com.

Reference Documentation

[1] ZED-F9P Integration manual, UBX-18010802
[2] u-center User guide, UBX-13005250
[3] u-blox F9 HPG 1.32 Interface description, UBX-22008968
[4] C099-F9P application board User guide, UBX- 18063024
[5] EVK-F9P-01 evaluation kit User guide, UBX-22038408  
[6] NEO-D9S Integration manual, UBX-19026111
[7] u-blox Knowledge Base – Services Support

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