Galileo HAS live stream

category: Gnss

Introduction

The European navigation satellite system Galileo broadcasts HAS (high accuracy service) augmentation information to improve positioning accuracy. This E6B signal can be received by Pocket SDR, NovAtel OEM729, Septentrio mosaic-X5.

However, there does not currently appear to be a way to leverage that information. So here’s a live stream of HAS information coming out of my OEM729 receiver.

HAS live stream

The raw data of OEM729 received at GNSS observation station will be distributed by NTRIP (Networked Transport of RTCM via Internet Protocol). NTRIP is a standard method for transmitting satellite positioning information over the Internet. Here are the addresses, ports and mount points:

addressportmount pointraw message name
ntrip.phys.info.hiroshima-cu.ac.jp80HASNovAtel GALCNAVRAWPAGE

Anyone is welcome to use this live stream without prior notice. I also publish live streams of Allystar receiver raw data on CLAS and MADOCA mount points.

However, how the HAS information is used is currently unknown. For example, setting this information to RTKNAVI Correction in RTKLIB does not improve positioning accuracy.

Due to organizational changes, the operation of this RTK reference station after 2024-08-31 is undecided. I would like to do various experiments in the rest of the year.

HAS information observation by QZS L6 Tool

Therefore, I modified the open source software QZS L6 Tool to decode the contents of this live stream. Here we use nov2has.py in the python directory. This code receives NovAtel binary format Galileo C/NAV (commercial navigation) message information from standard input and outputs the decoded HAS information to standard output. If you have already downloaded QZS L6 Tool with git, please execute git pull to update the software.

Here, we use RTKLIB’s command line application str2str to access the above live stream.

The video above is a recording of the display of live stream HAS information. For this shoot, I ran the following commands:

str2str -in ntrip://ntrip.phys.info.hiroshima-cu.ac.jp:80/HAS 2> /dev/null | nov2has.py -t 2

The numerical value of the -t option of nov2has.py indicates the detail of the information display. The default value of 0 displays only the augmentation items, 1 displays their contents, and 2 further displays bit images.

Comparison of MADOCA-PPP and HAS

MADOCA-PPP (multi-GNSS advanced orbit and clock augmentation - precise point positioning) is one of the augmentation signals broadcast by Japan’s Quasi-Zenith Satellite, Michibiki. Comparisons between MADOCA-PPP and HAS are often discussed. Therefore, I summarize the content of the augmentation messages.

augmentationMADOCA-PPPHAS
satellite systemST1Mask
orbitST2Orbit
clockST3Clock fullset, (Clock subset)
code biasST4Code bias
phase biasST5(Phase bias)
user range accuracyST7

MADOCA-PPP identifies messages by subtype (ST). In the table, parentheses indicate the messages have been defined but have not yet been broadcast.

What they have in common is that they first define the target augmentation satellites and then transmit the specific augmentation values.

The satellite time (clock) observations fluctuate more frequently than other observations. In MADOCA-PPP, the augmented values are frequently transmitted in ST3. On the other hand, HAS seems to have a policy of performing substantial reinforcement by frequently broadcasting reinforcement values for code bias.

HAS does not appear to broadcast a phase bias augmentation value at this time. On the other hand, MADOCA-PPP broadcasts phase bias as ST5. It is known that using a phase bias augmentation value can improve positioning accuracy by a method called ambiguity resolution (AR). [MADOCALIB](https://qzss.go.jp/technical/dod/madoca/madoca_test-library. html) has a sample program rnx2rtkp for high-precision positioning using AR.

HAS target satellite systems are GPS and Galileo. On the other hand, MADOCA-PPP target systems are GPS, GLONASS, Galileo, and Quasi-Zenith Satellite (Michibiki).

Conclusion

A live stream of Galileo HAS is open so that we can observe HAS information.

In addition to MADOCA-PPP and HAS, high-precision positioning augmentation is broadcast from China’s BeiDou geostationary satellites C60 and C61 [PPP-B2b] (http://www. beidou.gov.cn/xt/gfxz/202008/P020200803362062482940.pdf). Currently Pocket SDR and mosaic-X5 receivers can receive this PPP-B2b signal. I have both of these receivers, so I will try to decode this message.

In recent years, disaster information transmission and navigation message authentication have been realized in navigation satellites. It is fun to follow new technologies in this field. I would like to enjoy the rapid development of the navigation satellite field.


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