Introduction to RTK

Training on GNSS, 8 JAN 2020
11:00-12:00
Kaito Kobayashi
Tokyo University of Marine Science and Technology
TUMSAT GNSS Lab

1Contents
1.

What is RTK2.

RTK applications

3.

How to build RTK environment

4.

RTK configuration on rover

5.

Where can I buy GNSS devices?

6.

Moving-base RTK

7.

Useful web sites

Download link of this presentation
https://1drv.ms/u/s!AidzfXwz4kDK5TGapdiZGWkcFYQD?e=G5zzbv

TUMSAT GNSS Lab

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1. What is RTK
RTK is high accuracy positioning method using “Base Station”.

Knownposition

Antennamm level Baseline vector
Antenna

Observation data

ReceiverInternetUHF,VHF

ReceiverBase Station

UserPosition

Rover
TUMSAT GNSS Lab3

1. What is RTK
If “Base station” is not fixed → Moving-base RTK
You can get precise relative position, angle between 2 antenna.

Phase Difference②

Phase Difference①

Baseline vector(Relative position)TUMSAT GNSS Lab

42. RTK applications
RTK can expand GNSS use field over traditional PNT (Positioning, Navigation, Timing).

TUMSAT GNSS Lab

52. RTK applications
RTKConstruction

RTK survey
andUAV mapping

Traditional optical survey
RTKMoving-base
RTKMachine control
using 3D dataandAttitude monitoring

Complex machine control
TUMSAT GNSS Lab6

2. RTK applications
ITS (Intelligent Transportation System)

RTK

SPP

Auto driving support
Car navigation

RTK
Moving-base
RTK

Road pricing by lane

Distance control
TUMSAT GNSS Lab

72. RTK applications
Maritime

RTK
Moving-base
RTK

SPP

Seabed survey

RTK

Ship navigation

Moving-base
RTK

RTK
Moving-base
RTK

Auto berthing

Drilling, Maritime construction
TUMSAT GNSS Lab

82. RTK applications
UAVMoving-base
RTKSPP

AttitudeMonitoring
Moreprecise map

RTKRTKMapping

RTK Drone
TUMSAT GNSS Lab

Distributed type
Ground Control Point92. RTK applications
Agriculture Machinery GuidanceAgriculture

RTK-RTKSPP

Shift to young generation
Effective working

TUMSAT GNSS Lab103. How to build RTK environment
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.
Antenna

ReceiverAntenna

Rover (User)

Receiver

PCInternet

Ntrip
castersoftware

Ntrip
serverAntenna

ReceiverRover (User)
Antenna

ReceiverRover (User)TUMSAT GNSS Lab

113. How to build RTK environment
Base station antenna
Install antenna in open sky & static environment.

Japanese government base station

Our University base stationTUMSAT GNSS Lab

Temporary base station

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3. How to build RTK environment
Base station antenna
There is many kind of antenna in the market. Choose which can receive GNSS signal you want to use.

• Antenna Type

Choke ring

Patch antenna
with ground plane

HelicalPatch antenna
without ground plane

Good performance but High cost
TUMSAT GNSS Lab

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3. How to build RTK environment
Base station antenna
There is many kind of antenna in the market. Choose which can receive GNSS signal you want to use.

• Frequency

NavICSPSGPSQZSS
L5

GPSQZSS

QZSS
L6

BeiDouB3

BeiDou
B1

GPS
QZSS

TUMSAT GNSS Lab

Check datasheet

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3. How to build RTK environment
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.

https://www.use-snip.com/kb/knowledge-base/an-rtcm-message-cheat-sheet/

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3. How to build RTK environment
Base station receiver selection
Low cost
receivers are
now available!
Net-R9AsteRx-SB
NET-G5

AsteRx-m2a
OEM7
Delta-3
HD9300

F9P
Piksi Multi

M8T

Survey grade but
we can’t buy…

M8P

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3. How to build RTK environment
Base station receiver setting
Change receiver configuration to output RTCM message from USB port.
Here I will show example using u-blox F9P and Septentrio AtseRx-m2a

TUMSAT GNSS Lab

173. How to build RTK environment
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-ProcessKinematic).
AntennaFree 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

Don’t over
60km distance

ReceiverYour base station

Rinex data

Nearest basestation

PPK byRTKLIBTUMSAT GNSS Lab18

3. How to build RTK environment
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.

Antenna

IGS product.sp3 & .clk data

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-PPPReceiverRinex data

PPP byRTKLIB/Net_DifforSubmit Rinex data
PPP byRTKLIB/NetDiff

IGS product : (http://mgex.igs.org/IGS_MGEX_Products.php)
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3. How to build RTK environment
Base station antenna position
Sample of PPP solution

Net_Diff + MGEX productUse this position as your base station position.
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Trimble RTX service203. How to build RTK environment
Base station antenna position
Unless there is a special reason, I don’t recommend to use optical survey position or SPP averageposition for the base station position.
Traditional optical survey

Bias of SPP

Local survey coordinate has a gap
with GNSS coordinate (ITRF).

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3. How to build RTK environment
Get Ntrip server• RTK2GOFree Ntrip server. You can create your mount point and broadcast data.
Other server• BKG
https://igs.bkg.bund.de/ntrip/download

http://www.rtk2go.com/
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3. How to build RTK environment
Push out data to Ntrip server• RTKLIB STRSVR (Free)TUMSAT GNSS Lab23

3. How to build RTK environment
Push out data to Ntrip server• SNIP (Lite is Free)

https://www.use-snip.com/pricing/NtripserverReceiver

Serial port input
from the receiver

Push out data toyour mount pointTUMSAT GNSS Lab24

3. How to build RTK environment
Push out data to Ntrip server
You can check your Mount Point from “NTRIP Browser” in RTKLIB.

Your base station addressTUMSAT GNSS Lab25

4. RTK configuration on roverRover antennaSame manufacturer antenna with base station is recommended.
However, there is not much degradation between antennas from other manufacturers.

Choke ringPatch antenna
with ground plane

HelicalPatch antenna
without ground planeHigh performance

Portable and low cost
TUMSAT GNSS Lab

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4. RTK configuration on rover
RTK (Septentrio with PC)

Select base station

Input to COM17 port

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

2 COM port
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4. RTK configuration on rover
RTK (Septentrio with smartphone)Android app that supports septentrio receiver.

https://play.google.com/store/apps/details?id=com.septentrio.pinpointgis&hl=en

RTCM correction dataBluetooth

RTK Solution

TUMSAT GNSS Lab28

4. RTK configuration on rover
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 andclick “OK”.

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4. RTK configuration on rover
RTK (ublox with smartphone)Android app of Ntrip client.

https://play.google.com/store/apps/details?id=com.lefebure.ntripclient&hl=en

RTCM correction data
You need to setup ublox’s UART port that connect withBluetooth module
・Input : RTCM
・Output : NMEA・Baud rate : Same with Bluetooth module.

RTK Solution (NMEA)TUMSAT GNSS LabBluetooth30

4. RTK configuration on rover
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.

Supported “raw data” formats
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4. RTK configuration on rover
RTK (RTKNAVI)
Receiver configuration on u-center.
First, select COM port of the receiver and connect. Then open “message view”.
Open message viewDevice Manager

Select port

Receiver COM port
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4. RTK configuration on rover
RTK (RTKNAVI)
Receiver configuration on u-center. Open message view from View>Message View.
You need to click “send” after change configuration.

Right click -> “Enable”
Click “Send”
Enable output of RAWX & SFRBX (UBX-RXM )Setting to output UBX format (UBX-CFG-PRT)TUMSAT GNSS Lab

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4. RTK configuration on rover
RTK (RTKNAVI)
After receiver configuration was completed, save it and disconnect receiver.

“Disconnect”

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4. RTK configuration on rover
RTK (RTKNAVI)Open RTKNAVI.

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4. RTK configuration on rover
RTK (RTKNAVI)
Set input stream.

Select Ntrip mount pointTUMSAT GNSS Lab

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4. RTK configuration on rover
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 caseTUMSAT GNSS Lab

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4. RTK configuration on rover
RTK (RTKNAVI)
Set option to calculate RTK.
After option setting, click“Start” and then RTK starts.

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5. Where can I buy GNSS devices?
I show some shop that you can buy GNSS devices.
Antenna

AliExpress

Eltehs GNSS OEM StoreTUMSAT GNSS Lab

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5. Where can I buy GNSS devices?
Antenna

Ardusimple

ebay
TUMSAT GNSS Lab40

5. Where can I buy GNSS devices?
Receiver

AliExpress(ublox, Trimble, Novatel)TUMSAT GNSS Lab

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5. Where can I buy GNSS devices?
Receiver

Eltehs GNSS OEM Store (ublox)

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5. Where can I buy GNSS devices?
Receiver

Ardusimple (ublox)

ublox direct shop

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5. Where can I buy GNSS devices?
Receiverswift direct shop

Septentrio direct shop
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5. Where can I buy GNSS devices?
Cable & connector

SMA or TNC type connector are major in GNSS.

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6. Moving-base RTK
Moving-base RTK (AsteRx-m2a)
Just connect 2 antenna to the receiver.

ASCII output by nmea “HDT” message.
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6. Moving-base RTK
Moving-base RTK (F9P)
Hardware configuration.
GNSSantenna 2

GNSS
antenna 1

ublox F9P
（Rover)TX
UART1 RXGND

USB COM portPCu-centerublox F9P(Base)RXTX UART1
GND

5V power
supplyTUMSAT GNSS Lab

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6. Moving-base RTK
Moving-base RTK (F9P)
Base configuration.

Set protocol out of used UART to RTCM. Baudrate should be over
115200. (UBX-CFG-PRT)At UBX-CFG-MSG enable following message to output from used
UART.
RTCM3.3 1077 (GPS)RTCM3.3 1087 (GLONASS)
RTCM3.3 1097 (Galileo)
RTCM3.3 1127 (BeiDou)
RTCM3.3 4072.0 (For Moving-Base special message)
RTCM3.3 4072.1 (For Moving-Base special message)TUMSAT GNSS Lab

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6. Moving-base RTK
Moving-base RTK (F9P)
Rover configuration.

Set protocol in of used UART to RTCM. Baudrate should be over
115200. (UBX-CFG-PRT)

Enable RELPOSNED (UBX-NAV)TUMSAT GNSS Lab

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6. Moving-base RTK
Moving-base RTK (F9P)

Solution is shown in UBX-NAV-RELPOSNED message
There is no ASCII output and UBX format decode is necessary forapplication use.
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6. Moving-base RTK
Moving-base RTK (RTKNAVI)
Hardware Configuration
GNSS
antenna 2

GNSSantenna 1

reciever1

reciever2

USB COM port

USB COM port
PC

RTKNAVITUMSAT GNSS Lab

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6. Moving-base RTK
Moving-base RTK (RTKNAVI)
Receiver configuration (both receiver).

Setting to output UBX format (UBX-CFG-PRT)

Enable output of RAWX & SFRBX (UBX-RXM )TUMSAT GNSS Lab

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6. Moving-base RTK
Moving-base RTK (RTKNAVI)RTKNAVI set up.

Select “Serial” in bothrover and base andformat is “u-blox”.

Select COM port
number.

Select output format
to “E/N/U-Baseline”.
If you want to show
in RTKPLOT, set one
output stream to TCP.

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6. Moving-base RTK
Moving-base RTK (RTKNAVI)
Option configuration•••"Fix and Hold" is recommended in “Integer AmbiguityRes” setting.
If 2 antenna relative length is not changed, set“Baseline Length Constraint” is better.
(Input value islength between 2 antenna [m]/length error level[m])Without highlighted in red are default values.

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6. Moving-base RTK
Moving-base RTK (RTKNAVI)

Change shown format type by this button.
ENU or PYLTUMSAT GNSS Lab55

6. Moving-base RTK
RTKNAVI PLOT configuration

Click “Connect button”
after input setting.
Rover antenna
position

Base antenna
positionOpen another RTKPLOT.
Select TCP server from File>Connection
Setting and select port which defined in
RTKNAVI output stream.
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7. Useful web sites
Useful web sites for your RTK experiment• https://www.ardusimple.com/blog/• http://rtkexplorer.com/how-to/posts-getting-started/• http://www.denshi.e.kaiyodai.ac.jp/gnss_tutor/base_station.html• https://home.csis.u-tokyo.ac.jp/~dinesh/

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