AgOpenGPS with rtknavi and u-Blox NEO-M8T configuration guide

ibernat · 11 February 2020 17:34

Here my config to use u-Blox NEO-M8T with Agopengps
note now I use a cheap antena and is difficult to get “Fixed”. With better antena and better signal to noise ratio I hope to get a better solucion.

as a new user I can not upload images and add links* can some one help with this?

Hardware components:

u-Blox NEO-M8T
usb-ttl

Software components:

u-center (only for initial M8T config) hxxps://www.u-blox.com/en/product/u-center
RTKNAVI 64 hxxps://github.com/tomojitakasu/RTKLIB_bin/tree/rtklib_2.4.3
com0com hxxp://com0com.sourceforge.net/
Agopengps

Ntrip corrections:

In Catatalonia we have the Institut Cartogràfic i Geològic de Catalunya that provides free ntrip corrections for Catalonia region. (hxxp://catnet-ip.icgc.cat you can register for free)
Also for other Spanish regions the Instituto Geografico Nacional provides free corrections hxxp://www.ign.es/web/ign/portal/gds-gnss-tiempo-real

First, with u-center we need to configure the module. To connect the module to computer with USB port you need a USB to TTL adaptor (I recommend with the chip CP2102 or CP2104)
select de baudrate to 115200 and Protocol out UBX+NMEA:
ubloxport
The rate shoud be ok 1 per second (the correction rate from catnet-ip.icgc.cat is 1hz) more rate can saturate the gps module! (5 can be ok but better as low as possible if it works fine.)
(upload://2r5QOoeXTLle6v2SJ1QcudxQUoX.png)
If you are in Europe select only gps,sbas,galileo and glonass
(upload://uKte2BrZ5Ie2kmHbfXTtag8uLTA.png)
Enable UBX messages for UART and USB 02-13 and 02-15
(upload://nYjuE83cAdxC3aTjG59JjJEq7id.png)
upload://38kiADfq2MzFjpccX8DQIUNTtLJ.png)
Remember to save the settings to flash, if not on powerloss the settings are cleared!
(upload://p0UGAuDUkKxmqT5MgERtej03rrF.png)

Once the module is configured we need to create a virtual pair serial COM ports. This is to transfer the corrected NMEA from rtklib to Agopengps (once installed, simply click on “AddPair” and remember the port numbers! i my example com1 and com 2)
(upload://70IMM749zttjwPCEVqJSVNug9zM.png)

Now is time to get the RAW UBX satellite observation from neo-m8t to RTKNAVI64 and apply the ntrip correction and output a NMEA to COM1
(upload://iGoLFZG51hL2wJoLZPuB9w01FMP.png)
Serial Options COMport where is the M8T module and speed 115200, format u-Blox
Mount point must be someting like VRS3 and the Format must be RTCM3
(upload://W5MWNunlf5D5LgDwz7QU5tkQRG.png)
Output Stream is the corrected NMEA to transfer to Agopengps, to do so, we configure the Virtual COM port we created before (my case COM1 and speed 115200)
(upload://79Pyp4Z8Yoqqw4R0O8HF3fhCmCG.png)
Other options
upload://tYHNM8F6dPwHSjPv0NCgRhemyRG.png) (upload://v2f6fnuNmoRzogPij4BWwoetChX.png)

And finally configure AgopenGPS to use the corrected NMEA from COM2
(upload://797AGrfmdCnrHQqBJbOrSIwunGq.png)

Final Note; with the module u-blox ZED-F9P all of this is not necessary but the price is 200 euros VS 50 euro

ibernat · 12 February 2020 18:53

Here my config to use u-Blox NEO-M8T with Agopengps
note now I use a cheap antena and is difficult to get “Fixed”. With better antena and better signal to noise ratio I hope to get a better solucion.

Hardware components:

u-Blox NEO-M8T
usb-ttl

Software components:

u-center (only for initial M8T config) u-center
RTKNAVI 64 GitHub - tomojitakasu/RTKLIB_bin at rtklib_2.4.3
com0com http://com0com.sourceforge.net/
Agopengps

Ntrip corrections:

In Catatalonia we have the Institut Cartogràfic i Geològic de Catalunya that provides free ntrip corrections for Catalonia region. (http://catnet-ip.icgc.cat you can register for free)
Also for other Spanish regions the Instituto Geografico Nacional provides free corrections Instituto Geográfico Nacional

First, with u-center we need to configure the module. To connect the module to computer with USB port you need a USB to TTL adaptor (I recommend with the chip CP2102 or CP2104)
select de baudrate to 115200 and Protocol out UBX+NMEA:
ubloxport
The rate shoud be ok 1 per second (the correction rate from catnet-ip.icgc.cat is 1hz) more rate can saturate the gps module! (5 can be ok but better as low as possible if it works fine.)
rates
If you are in Europe select only gps,sbas,galileo and glonass
ubloxgnss
Enable UBX messages for UART and USB 02-13 and 02-15 ubloxmsg211 ubloxmsg215
Remember to save the settings to flash, if not on powerloss the settings are cleared!
ubloxcfg

Once the module is configured we need to create a virtual pair serial COM ports. This is to transfer the corrected NMEA from rtklib to Agopengps (once installed, simply click on “AddPair” and remember the port numbers! i my example com1 and com 2)
virtualCom

Now is time to get the RAW UBX satellite observation from neo-m8t to RTKNAVI64 and apply the ntrip correction and output a NMEA to COM1
rtknavi general
Serial Options COMport where is the M8T module and speed 115200, format u-Blox
Mount point must be someting like VRS3 and the Format must be RTCM3
ntrip
Output Stream is the corrected NMEA to transfer to Agopengps, to do so, we configure the Virtual COM port we created before (my case COM1 and speed 115200)
output
Other options
setting1 settings2

And finally configure AgopenGPS to use the corrected NMEA from COM2
gpsPort

Final Note; with the module u-blox ZED-F9P all of this is not necessary but the price is 200 euros VS 50 euro

ptd006 · 12 February 2020 21:03

Thanks, I have an M8T sat on my desk waiting to setup with RTKlib- your guide will be handy.

MylArti · 12 February 2020 21:09

Can we filter out unnecessary NMEA sentences in RTKNAVI.
GGA and VTG are only needed.

Brofarm · 12 February 2020 21:36

Some reading for you @MylArti… RTKlib manual.
Last time I read through, I think you can select output messages!

Brofarm · 12 February 2020 22:10

Just had another quick read…
Solution Format
Set the output solution format. ‐ Lat/Lon/Height : Latitude, longitude and height ‐ X/Y/Z‐ECEF : X/Y/Z components of ECEF coordinates ‐ E/N/U‐Baseline: E/N/U components of baseline vector ‐ NMEA0183 : NMEA GPRMC, GPGGA, GPGSA, GLGSA, GAGSA, GPGSV, GLGSV and GAGSV
outsolformat
For RTKNAVI, specify options as Output Streams setting.

…… I don’t actually see VTG, although it should be part of NMEA0183 ?

Brofarm · 12 February 2020 22:47

@ibernat how well are you finding 1hz?
I have m8t just doing dgps at the moment @4.8hz and was thinking it was borderline for speed.

At 1hz and you are driving at 10km/h , that 2.77m travelled each fix (if my maths correct?)!

ibernat · 13 February 2020 09:00

@Brofarm, I haven’t tested my setup on field, because the GPS antenna is the free one I got with the module. (small square antenna with IPEX connector)
On RTKNAVI to get a FIX position the signal to noise ratio of 6 satellite must be around 50, if you see my screenshot is about 30-40 and most of the time I’m Floating.

I selected 1Hz because the NTRIP provider, provides one correction per second, I would like to test with that value, but provably I’ll have to increase at least 5Hz (I don’t know the limit for M8T)

Brofarm · 13 February 2020 09:16

The limit is 5hz with SBAS active.

minolu-JP · 13 February 2020 14:14

VTG is not output in RTKLIB NMEA0183

github.com

tomojitakasu/RTKLIB/blob/rtklib_2.4.3/src/solution.c

/*------------------------------------------------------------------------------
* solution.c : solution functions
*
*          Copyright (C) 2007-2020 by T.TAKASU, All rights reserved.
*
* references :
*     [1] National Marine Electronic Association and International Marine
*         Electronics Association, NMEA 0183 version 4.10, August 1, 2012
*     [2] NMEA 0183 Talker Identifier Mnemonics, March 3, 2019
*         (https://www.nmea.org/content/STANDARDS/NMEA_0183_Standard)
*
* version : $Revision:$ $Date:$
* history : 2007/11/03  1.0 new
*           2009/01/05  1.1  add function outsols(), outsolheads(),
*                            setsolformat(), outsolexs, outsolex
*           2009/04/02  1.2  add dummy fields in NMEA mesassage
*                            fix bug to format lat/lon as deg-min-sec
*           2009/04/14  1.3  add age and ratio field to solution
*           2009/11/25  1.4  add function readsolstat()
*           2010/02/14  1.5  fix bug on output of gpstime at week boundary

This file has been truncated. show original

However, the direction of travel can be obtained from AOG’s [GPS Heading From] -[Fix to Fix Calc].

Until last year I used two pairs of M8P and TW2710 Antenna. In open sky, within 5km, more than 90% fix was obtained.
(use GPS,BDS,QZSS .(base)UBXraw:ntrips -(rover)UBXraw:serial.5Hz)

ibernat · 1 March 2020 08:31

Hi,

After some test with the neo-M8T I arrived to the conclusion that is not a good module to use as a single device for acuracy.
The module price is about 60 euro, is a single frequency and you need a good antenna to get stable FIX position. In total you need to spend +200euro for this solution.

With the module zed-f9p is a bit more expensive, but because is dual frequency, with a 100 euro antenna and NTRIP internet correction you get a better solution. And the total price is less than 300euro. For less than this I think is difficult to get an stable accuracy.

Some of you has the same opinion?

NorthernFarmer · 1 March 2020 09:27

I’m not familiar with M8T at all but I assume it would work reasonably well if the distance to base was not too large. Minolu-JP seems to confirm this. Using a pair of M8T receivers could be a low cost option, one as a base, the other one as a rover?

Note that the 1 Hz RTK correction data rate does not limit the receiver to 1 Hz measurement rate. 1 Hz is too low from most Ag applications but you can go as high as the receiver allows while still keeping 1 Hz correction data rate (I assume you cannot even change that from a public source).

Why would one want to have SBAS included when aiming for RTK? For fall back? I’d disable SBAS if that allows faster RTK position measurements.

Anyway, very useful instructions. Interesting also for us who are not using the M8T receiver.

jpm · 15 March 2020 22:13

when i use the rtknavi and com0com solution it works, but when i connect autosteer or trunk cut, the gps com gets blocked and no longer receives data

MylArti · 31 March 2020 06:52

Hi @jpm I am interested of your com0com-setups, because mine seems to be working. I made one COM port pair COM (10) - COM (13). The solution sends the data to COM (10) and AutoSteerboard reads that data from port COM (13).

ptd006 · 18 July 2020 15:20

Hi @ibernat,

I have done some testing with my M8T.

conclusion that is not a good module to use as a single device for acuracy.

With rtknavi, a base station about 30km away (via rtk2go.com), 5hz refresh, the cheap antenna it came, and DIY “grounding plate” (old CD side down, not sure if it’s actually helping!) I am getting decent results (well, better than expected and good enough for my projects). It’s usually in float but in my naive tests (moving it around in measured patterns) it’s <5cm accuracy (at least relatively) and stable. There is drift near buildings though.

Note- after I unzipped and ran rtknavi I think the position for the base (in options) was set (to a wrong value)- should take position from NTRIP stream.

aleks115 · 7 May 2021 09:02

first of all sory my englis is bad… i have some trubles whit seting up the neo m8t … im not shure why… so i make all the steps like up in the pictures but whit the bauthreate 115200 wont work its looks like the 9600 works only? it looks like i do have some conections and signal wit rtklib but no corection steream the closest rtk base is 100 km away i konw its farr but i just wann try make the rower work first. if it works so i can order hardware fore base station… so any advice wold be helpful tnx