GNSS Data Processing for High-Accuracy Positioning using Low-Cost Receiver Systems 11 – 13 JAN 2022 Kaito Kobayashi, Tomohiro Ozeki, Nobuaki Kubo Tokyo University of Marine Science and Technology TUMSAT GNSS Lab 1. What is RTK 2. RTK applications 3. How to build RTK environment 1. Base-Station 1. Receiver and Antenna types 2. How to setup base-station 2. Rover Unit 1. Receiver and Antenna Types 2. How to setup rover
4.
Data Recording and Format Conversion for RTK 1. SBF, UBX, JPX etc. to RINEX 2. Which version of RINEX shall be used?
TUMSAT GNSS Lab
2 Base Station Rover TUMSAT GNSS Lab 3 If “Base station” is not fixed → Moving-base RTK You can get precise relative position, angle between 2 antenna. m2a.serial - Attitude View - S/N 3034498 -口X View  Help
Mode: GNSS-based (auto)  Fix Ambiguities Pitch: Roll: Moving baseline setup for precise Phase Difference ② Phase Difference TUMSAT GNSS Lab 4
RTK can expand GNSS use field over traditional PNT (Positioning, Navigation, Timing).
◆Construction TUMSAT GNSS Lab 6
◆ITS (Intelligent Transportation System) TUMSAT GNSS Lab 7
◆UAV wore precise MSM Ground Control -Point- TUMSAT GNSS Lab 9
◆Agriculture TUMSAT GNSS Lab
◆Base station overview I explain the most common broadcast way using “Ntrip server”. However you can also use VHF/UHF radio, Bluetooth, LAN or cable communication to broadcast base station data. TUMSAT GNSS Lab
◆Base station antenna Install antenna in open sky & static environment. Japanese government base station Our University base station Temporary base station
◆Base station receiver selection The receiver should support raw data output. • RTCM3 Standard format for RTK. Select base station position and observation message is must. •  Receiver manufacturer format Binary message. Input support is depend on the rover receiver. RTCM Rev3 Common Message Types 1005 Stationary RTK Reference Station ARP  X 1006 Stationary RTK Reference Station ARP plus the Antenna Height  X 1007 Antenna Descriptor (msg 1008 (X) is also commonly used) X nded L1&L2 GLONASS RTK Observables, the other main msg  X https://www.use-snip.com/kb/knowledge-base/an-rtcm-message-cheat-sheet/
3.1.5.1 RTCM correcti
Configure input of differential correcti
The format of the differential corrections output by th with what is accepted by the Rover.  In the Corrections Input window of the Corrections menu, you can configure the AsteRx SB to only accept differential corrections of a particular The default ‘auto’ setting will accept correction data format format. CMR+, To modify the RTCM input/output settings, see the configuration section in the u-blox ZED-F9P Interface Description [ 2 ]
◆Base station receiver setting Change receiver configuration to output RTCM message from USB port. Here I will show example using u-blox F9P.
◆Base station antenna position You need to know your base station antenna position with cm level accuracy. • RTK If  there is another RTK base station near your base, you can calculate by PPK (Post-Process Kinematic). Free RTK base stations. -IGS station http://www.igs.org/network datalink : ftp://cddis.gsfc.nasa.gov/gnss/data/daily -Local CORS https://www.chcthailand.com/cors-picture PPK by RTKLIB
TUMSAT GNSS Lab

◆Base station antenna position You need to know your base station antenna position with cm level accuracy. • PPP If  there is no another RTK base station, calculate by PPP.
Free PPP service
- RTKLIB with IGS product ( http://www.rtklib.com/ - Net_Diff with IGS product ( https://github.com/YizeZhang/Net_Diff) - Trimble RTX ( https://www.trimblertx.com/UploadForm.aspx - CSRS-PPP (https://webapp.geod.nrcan.gc.ca/geod/tools-outils/ppp.php) - MADOCA-PPP IGS product： ( http://mgex.igs.org/IGS MGEX Products.php ) PPP by TKLIB/NetDiff
TUMSAT GNSS Lab

◆Base station antenna position Sample of PPP solution Net_Diff + MGEX product Use this position as your base station   Trimble RTX service position.
◆Base station antenna position Unless there is a special reason, I don’t recommend to use optical survey position or SPP average position for the base station position.
◆Push out data to Ntrip server You can check your Mount Point from “NTRIP Browser” in RTKLIB.
◆RTK (Septentrio with PC) Use Ntrip client function of “Data Link” in “RxTools” https://www.septentrio.com/en/products/software/rxtools Downloand link https://www.septentrio.com/en/support/software/rxtoolsト(COMとLPT) com0com - serial port emulator CNCA1 (COM40) com0com - serial port emulator CNCB1 (COM41) Active Management Technology - SOL (COM3) I USB COM Port 1 (COM17) Septentrio Virtual USB COM Port 2 (COM16)清信ホート(COM1)マウスとそのほかのポインティングデバイス
◆RTK (ublox with PC) Use Ntrip client setting in u-center. https://www.u-blox.com/en/product/u-center NTRIP client setting Receiver>NTRIP Client Select mount point and click "OK". RTK support is  M8P and F9P

◆RTK (RTKNAVI)
Real time RTK engine that supports many receivers. To use RTKNAVI, first you should set receiver to output "raw data". "raw data" means binary observation message include RTCM. RTKNAVI decodes this "raw data" and calculate RTK solution. Here, I show the example using u-blox receiver.
◆RTK (RTKNAVI) Receiver configuration on u-center. First, select COM port of the receiver and connect. Then open "message view".
◆RTK (RTKNAVI) Receiver configuration on u-center. Open message view from View>Message View. You need to click "send" after change configuration. Enable output of RAWX & SFRBX (UN Setting to output UBX format (UBX-CFG-PRT)
◆RTK (RTKNAVI) After receiver configuration was completed, save it and disconnect receiver.
◆RTK (RTKNAVI) Open RTKNAVI. RTKLIB v.demo5 b33a
TUMSAT GNSS Lab

◆RTK (RTKNAVI) Set input stream.
骨ポート(COMとLPT)
🌸 com0com - serial port emulator CNCA1 (COM40) 👍🏻  com0com - serial port emulator CNCB1 (COM41) 🌸  Intel(R) Active Management Technology - SOL (COM3)
TUMSAT GNSS Lab

◆RTK (RTKNAVI) Set output stream & log stream. Here the RTK position will be written to the file. Also you can choose other option (TCP, Serial) according to your use case Base SYS SNR (dEHz)
TUMSAT GNSS Lab

◆RTK (RTKNAVI)
Set option to calculate RTK. After option setting, click “Start” and then RTK starts.
◆RTK post processing need GNSS raw data. ◆After changed the configuration of the receiver to output raw observation, you need to record it. ◆Most of the receivers output its data stream by serial communication. ◆Easy way to record the data on PC is use RTKLIB.
◆Data recording (STRSVR) RTKLIB v.demo5 b33a STRSVR ver.demo5 b33c Start recording目ポート(COMとLPT) com0com - serial port emulator CNCA1 (COM40) com0com - serial port emulator CNCB1 (COM41)  Intel(R) Active Management Technology - SOL (COM3) 👍🏻 USBシリアルデバイス(COM11)鳥 退信ホート(COM1) File Options × Output File Path | TimeTag File name Tips
TUMSAT GNSS Lab

◆GNSS raw data is normally original binary format by receiver manufacturer. ◆To use raw data on third party RTK software, we need to convert it to RINEX format. ◆About RINEX format > https://www.igs.org/wg/rinex/ ◆RTKCONV on RTKLIB can convert several manufacturer’s receiver data.
◆Data conversion (RTKCONV) RTKLIB v.demo5 b33a W  RTKCONV ver.2.4.3 b33 ■ X Time Start (GPST) Time End (GPST) 2000/01/01 2000/01/01 ■ ■ 00:00:00 Interval GNSS raw ect receiver $9956$416$ file with RINEX format .nav is ephemeris file with RINEX format
TUMSAT GNSS Lab

◆Data conversion (RTKCONV) RTKLIB v.demo5 b33a WR RTKCONV ver.2.4 ] Time Start (GPST) Output RINEX version. Recommend upper Recommend check “Scan Obs Types” Satellite constellations you want to output Recommend check C: Code range L: Carrier phase D: Doppler shift S: SNR GNSS frequencies you want to use Recommend check all for general purpose TUMSAT GNSS Lab
◆Data conversion (RTKCONV) After conversion you can find .obs file and .nav file which can open with text editor.
◆Data conversion (RTKCONV) You can also check RINEX format data graphically by RTKPLOT. SSLab¥2022¥ICG Training¥RTKdata 01¥DynamicData¥ECJ02 base & Plot.. Exit
◆Useful web sites for your RTK experiment • http://www.denshi.e.kaiyodai.ac.jp/gnss_tutor/base_station.html • https://home.csis.u-tokyo.ac.jp/~dinesh/ • http://www.rtklib.com/