Update of MADOCA-PPP wide-area ionospheric information coverage area

Introduction

The Quasi-Zenith Satellite (QZS), Michibiki, not only broadcasts positioning signals, but also positioning augmentation messages to improve positioning accuracy by combining them with satellite positioning.

One of these, MADOCA-PPP (multi-GNSS advanced orbit and clock augmentation - precise point positioning), estimates satellite-specific errors using a global ground observation network. This belongs to a technology called precise point positioning (PPP), and it takes about 15 to 30 minutes for stable coordinates to be output.

The Michibiki 6 (QZS-6) and 7 (QZS-7) satellites, scheduled to be launched next year, will provide wide-area ionospheric information that can output stable coordinates in a shorter time. This function can be tried using MADOCALIB and MADOCA-PPP Internet distribution (/en/madocalib12/). The wide-area ionospheric information used here can be read using the QZS L6 Tool (/en/qzsl6tool-20240816upd/#madoca-ppp-iono-display-with-qzsl6tool). The coverage area of ​​the wide-area ionospheric information observed at that time was limited to all of Japan and parts of Australia.

However, the MADOCA-PPP wide-area transmission information coverage area update was announced on December 2, 2024, and it is expected that MADOCA-PPP will enable short-time, high-precision positioning over a wider area. Let’s try to find the coverage area coordinates of this new wide-area ionospheric information.

Wide-area ionospheric information coverage area update

According to the information on the official Michibiki website (Coverage area of ​​MADOCA-PPP ionospheric correction data), the wide-area ionospheric information from QZS-7 covers Japan and eastern Australia. Meanwhile, that from QZS-6 covers northern Philippines, parts of Indonesia, and western Australia.

Though QZS-6 and QZS-7 have not yet been launched, we can obtain these messages via the MADOCA-PPP Internet broadcast and can observe their contents using QZS L6 Tool v.0.1.4.

Wide-area ionospheric information to be broadcast on QZS-7

The QZS-7 L6D signal will broadcast wide-area ionospheric information with PRN (pseudo random noise) number 201. The green area in the diagram in Coverage area of ​​MADOCA-PPP ionospheric correction data indicates ​​this wide-area ionospheric information. R stands for region number, and A stands for area number.

These coordinates can be read using the MADOCA-PPP archive, the curl command, the QZS L6 Tool’s qzsl6read.py, and the lv command. As an example, we will obtain and process data from 00:00:00 to 01:00:00 on December 5, 2024. The number of days since January 1 is 340, and the time code is A.

curl https://l6msg.go.gnss.go.jp/archives/2024/340/2024340A.201.l6 --output - | qzsl6read.py -t 1 -c | lv

When you run this command, you will get output similar to the following for message type (MT) 1, which defines the coordinates:

MT1 Epoch=00:00:06+4 UI=30s(5) MMI=0 IODSSR=0 Region=5  9014bit  NumAreas=8
 # shape lat[deg] lon[deg] lats lons / radius[km]
 1 RECT      43.7    142.5  2.5  4.3
 2 RECT      39.2    140.5  2.0  3.0
 3 RECT      34.2    140.0  3.0  2.5
 4 RECT      35.2    135.0  3.3  2.5
 5 RECT      32.8    130.3  2.8  2.2
 6 RECT      27.5    129.0  2.5  3.0
 7 RECT      24.5    124.2  1.0  1.8
 8 CIRCLE    26.9    142.2  100
 ...
 MT1 Epoch=00:00:30+4 UI=30s(5) MMI=0 IODSSR=2 Region=2  9623bit  NumAreas=9
 # shape lat[deg] lon[deg] lats lons / radius[km]
 1 RECT     -15.5    132.5  5.5  6.5
 2 RECT     -15.5    144.5  5.5  5.5
 7 RECT     -26.0    132.5  5.0  6.5
11 RECT     -23.7    143.5  2.7  4.5
12 RECT     -23.7    151.0  2.7  3.0
13 RECT     -28.7    143.5  2.3  4.5
14 RECT     -28.7    151.0  2.3  3.0
15 RECT     -35.2    146.5  4.2  7.5
16 RECT     -41.7    146.5  2.3  3.0
...

For area number 2, there were only two areas up until now, but this time nine areas were observed (area number 4 is no longer available). Load this data into Microsoft Excel and compile the rectangular coordinates of four points consisting of latitude (lat) and longitude (lon) (madoca-ionosphere-update.xlsx). Area numbers 5 and 8, the Ogasawara Islands, are not included in this table because they are circular areas.

Wide-area ionospheric information to be broadcast on QZS-6

The wide-area ionospheric information on the QZS-6 L6D signal is read in the same way. The PRN number is 200. The red area in the diagram is the coverage area of ​​this wide-area ionospheric information.

curl https://l6msg.go.gnss.go.jp/archives/2024/340/2024340A.201.l6 --output - | qzsl6read.py -t 1 -c | lv

...
MT1 Epoch=00:00:30+4 UI=30s(5) MMI=0 IODSSR=2 Region=1  3591bit  NumAreas=3
 # shape lat[deg] lon[deg] lats lons / radius[km]
 5 RECT     -34.0    132.5  3.0  6.5
 6 RECT     -31.5    119.5  4.0  6.5
 8 RECT     -20.5    119.5  7.0  6.5
 ...
 MT1 Epoch=00:00:33+4 UI=30s(5) MMI=0 IODSSR=2 Region=3  1404bit  NumAreas=2
 # shape lat[deg] lon[deg] lats lons / radius[km]
 1 RECT      17.4    121.4  1.3  1.1
 2 RECT      14.7    120.8  1.4  1.0
 ...
 MT1 Epoch=00:00:34+4 UI=30s(5) MMI=0 IODSSR=0 Region=4* 77bit  NumAreas=1
 # shape lat[deg] lon[deg] lats lons / radius[km]
 1 RECT      -6.8    107.0  0.9  1.2
 ...

I got wide-area ionosphere information for region 1 (western Australia), region 3 (northern Philippines), and region 4 (part of Indonesia). Amazing. I’ll put these together in another Excel sheet.

Conclusion

The coverage area of ​​the MADOCA-PPP wide-area ionospheric information has been updated, so I have compiled these coordinate values. I look forward to the launch of the new Michibiki satellites.