Waas gnss receiver

GPS / RTK / GNSS
21

Thanks for the document link. The document is unfortunately a bit old and actually brings confusion to this discussion when it says:
“2020+: It is planned that EGNOS will experiment a major evolution by 2025, EGNOS V3, including the fulfilment of the SBAS L1/L5 standard, expansion to dual-frequency, and evolution toward a multi-constellation concept.”

From that sentence I read that Galileo support will appear from about 2025 onwards as well as dual frequency support. Earlier from the thread I got the impression that dual frequency support would exist already.

22

Hello,

I admit, it’s not very clear. But I thinks my knowledge in GPS are too limited to fully understand.

Il found this old (2011) EGNOS user guide (sorry, it’s in French):

Chapter 10 Evolution, they said (sory, google translate, I was lazy to translate myself :grin:):
“In addition, EGNOS is fully interoperable with the GPS system which has currently entered a modernization phase. In fact, GPS will emit new civil signals on the L5 frequency band, thereby improving system performance. In addition, the European Galileo satellite navigation program should be operational from 2014 for the IOC (Initial Operations Capability) phase including a constellation of 18 satellites in total. This will be followed by the FOC phase (Full Operations Capability) which will see the complete Galileo constellation (27 satellites + 3 spares). A certain number of studies are underway to analyze the possible evolutions of EGNOS, in particular to take into account counts the corrections and the integrity: • of the GPS signals transmitted on L5, • of the signals transmitted by the Galileo system.”

On the Europeen Global Navigation Satellite Systems Agency website (they are in charge of EGNOS and Galileo), they said:
https://egnos-user-support.essp-sas.eu/new_egnos_ops/egnos-system/about-egnos
“EGNOS augments the GPS L1 (1575.42 MHz) Coarse/ Acquisition (C/A) civilian signal by providing corrections and integrity information for GPS space vehicles (ephemeris, clock errors) and most importantly, information to estimate the ionosphere delays affecting the user .”

Also in the EGNOS Open Service (OS)Service Definition Document, in the introduction, we found the same information:
“Presently, EGNOS augments GPS using the L1 (1575.42 MHz) Coarse/Acquisition (C/A) civilian signal function by providing correction data and integrity information for improving positioning, navigation and timing services over Europe.”.
But nothing on the L2 band.

So I thinks you are right since the beginning: EGOS provide a correction only for L1 GPS band C/A signal.

But when I look on the GPS Signal plan (GPS Signal Plan - Navipedia), C/A signal are transmited only on L1 band.
But which is not very clear to me is: why a L1/L2 receiver couldn’t use L1 C/A signal with EGNOS augmentation and in the same time the signals from L2 Band ? I thinks it’s this is where my knowledge in GPS too limited :slight_smile:.

I have to had the Novatel Introduction to GNSS (An Introduction to GNSS Book | NovAtel) book on the list of all the thinks I should read but I haven’t the time :sweat_smile:.

Math

23

Hello,

It seems that with the new firmware update, ZED-F9P support SBAS (WAAS & EGNOS):

Math

5 Likes
24

Great ! ! Don t need to look for another chip anymore !

25

Hi,
Apologies in advance for my lack of knowledge I’m fairly new to this! I’m currently running AgOpen GPS based in the UK using a 5Hz usb plug in receiver originally designed aimed at the marine industry however this is nowhere near accurate enough and jumps around all over. At the moment I’m only looking to use ag open GPS as a AB line lightbar tool for tasks such as fertiliser spreading on grassland however as I become more confident with the program I may consider making an Arduino based steering system. I’m hoping someone will be able to recommend a receiver that could be plugged in to the usb port and would be good enough to run ag open GPS, the cheaper the better!

Many Thanks
Harry

26

Hi Harry,

If you want to have a precise position in AOG, even to use it only as a steering bar, a GNSS reciever alone (even a high end marine one) can’t work. the GNSS position is not precise enough and requires some kind of correction.

If you wand a better precision, most people here go for a RTK setup. That’s what I did so I can really tell you about intermediate alternatives. RTK allows you to get 2 cm accuracy, which is enough for autosteer or for a steering bar. You may be able to feed your reciever with RTK correction (with RTCM messages format), give a look at the documentation. RTK correction can come from your own base station (another GNSS reciever is required, preferably the same as your rover, again check the documentation to see if it can output RTCM) or from a third party provider.

Otherwise, you will need another GNSS reciever. Most people here go for the dual band ZED-F9P, but some prefer a less expensive and less accurate single band module like the NEO-M8T. To get RTK you need two of them, one to setup a base station (senting RTCM messages) and one used as a rover in the tractor (recieving RTCM) and connected to AOG.

If you believe RTK is overkill for your application, you may want to try the WAAS / EGNOS / QZSS free correction with a ZED-F9P (if you’re in the USA / Europe or Japan), as mentionned above by Math.

You’ll find more detailed information in various threads of this forum

27

Hi,

I just arrived here and saw this thread. I used to work for the EGNOS development team at ESA. As discussed above, EGNOS currently only augments GPS L1 signals (embarassing for the EC, who own both Galileo and EGNOS) but with V3, EGNOS will augment both GPS and Galileo signals, hopefully to include L5/E5 signals. It has been suggested to me that the L5/E5 services from GPS and Galileo are likely to offer significantly better accuracy than L1, such that some users may not need WAAS or EGNOS. (L1 services are obliged to remain compatible with old receivers but the new L5/E5 services will be able to insert more information in the signals, providing greater accuracy and other features).

28

Try your F9P’s uncorrected. Tested Harrowing with a Stieger it was straighter than WAAS.

sM2corrected2

1 Like
29

Are you sure it wasn’t using SBAS at all? Interesting!

30

100% sure it was not set to SBAS, it was a Emlid M2 (f9p) you cannot enable it from their interface.

All constellations were enabled 35+ satellites in view, Trimble 150 you can change it to still steer without a fix.
Was it as good as RTK no, but it was noticeably better than running WAAS. Emlid was displaying 14cm (5.5") of uncertainty, and it certainly matched what was on the ground.

I am impressed by this little chip.

31

I can confirm f9p without waas works great for harrowing. Even works for combining but have to adjust line every little while.

2 Likes
32

te t’excuses pas