FROM_QIITA - HackMD

# FROM_QIITA ###### tags: `RTK-GPS` `EN` https://qiita.com/m_take/items/06892a8e25aa577e8455 # Objective We create guidance to assist straight traveling using GPS (GNSS) for tractors and rice planting machines. Since approximately an half year ago when I got the magazine which titled `` Transistor Technology '', I made it by myself and I struggled because when I started, because I had no experience in Programming and electronic kit. And finally, I could prove that it would be practical with this season's rice planting work, so I will introduce it. In the future, I would like to be able to use the steering motor to drive automatically. # Necessities(items) + Transistor technology released January 2018 http://toragi.cqpub.co.jp/tabid/865/Default.aspx + Transistor technology released Febrary 2019 There are details about how to use u-center and RTKLIB in a separete volume (RTK start-up manual). + Transistor technology RTK starter kit for moving, with GPS/Beidou antenna and Ublox NEO-M8P-0 module (RTK engin，RAW compatible)【TGRTK-B】￥21600 X 2 http://shop.cqpub.co.jp/hanbai/books/I/I000239.html + GPS antenna　Tallysman TW2710　￥11117 https://www.digikey.jp/product-detail/ja/tallysman-wireless-inc/33-2710-00-5000/1526-1014-ND/4862786 + raspberrypi3 ｘ 2 + smart phone（with deserting） + USB power port (12v -> more than 5v 2.4A） https://www.monotaro.com/p/1999/7653/ + electronic parts (USB cable, LED, resistor, keypad, etc.) It can be done within $1000 (one base station + one mobile station) (NEO-M8T ($ 75) instead of NEO-M8P https://www.csgshop.com/product.php?id_product=205 If you use RaspberryPiZEROW instead of RaspberryPi3, it can be made aroud ¥500,00.) Inexpensive receivers are also we can get, for example, using AgriBus-GMini , we can use RTK-GPS guidance with ¥59,800 × 2 units + Android tablet. https://agri-info-design.com/ https://agri-info-design.com/agribus-gmini/ # Reference links http://gpspp.sakura.ne.jp/index.shtml The website of creator of RTKLIB http://www.rtklib.com/prog/manual_2.4.2.pdf http://www.rtk2go.com/ Free NTRIP　Caster is provided # Conceptual diagram ![](https://i.imgur.com/8fakzla.png) # Reference station (Base) The output of M8P is u-center. ``` GNSS> GPS + BeiDou + QZSS MSG> 02-13 RXM-SFRBX 02-15 RXM-RAWX ``` + Please make them output from USB (for details, refer to a special site. Translation is written in last of this article. https://toragi.cqpub.co.jp/tabid/865/Default.aspx) + Next, about setting on Raspberry Pi. + Click here for details on how to install RTKLIB http://toragi.cqpub.co.jp/Portals/0/support/junior/article/2017/1704gnss.html + The base station uses the NTRIP server program on the str2str command line + How to use is on page 99 of manual 2.4.2 + In my settings, create the following executable file and give it execute permissions ```shell= #! /bin/sh cd /home/pi/RTKLIB/app/str2str/gcc ./str2str -in serial://ttyACM0:115200 -out ntrips://:BETATEST@rtk2go.com:2101/[MountID] ``` + Please replace [MountID] as appropriate. + Please refer to here so that it can be automatically executed by systemctl http://hendigi.karaage.xyz/2016/11/auto-boot/ # Mobile station (Rover) + Please install RTKLIB on in-vehicle use Raspberry Pi. + Rtk positioning program of rtkrcv command line is used for mobile station. + Make settings in the .conf file but my example can be found below. [MountID] + Latitude / Longitudinal altitude (ant2-pos *) of base station position should be replaced as appropriate. + The input is a base station ntripsvr via smartphone, mobile station is serial (USB) in ubx format. + Output is one of localhost: east-west-north-south distance from base station to port 52001 (enu). + Another is to put the latitude and longitude (llh) in the file every 0.2 seconds (5Hz). ```bash= # rtkrcv options for rtk console-passwd =admin console-timetype =gpst # (0:gpst,1:utc,2:jst,3:tow) console-soltype =dms # (0:dms,1:deg,2:xyz,3:enu,4:pyl) console-solflag =1 # (0:off,1:std+2:age/ratio/ns) inpstr1-type =serial # (0:off,1:serial,2:file,3:tcpsvr,4:tcpcli,7:ntripcli,8:ftp,9:http) inpstr2-type =ntripcli # (0:off,1: serial,2:file,3:tcpsvr,4:tcpcli,7:ntripcli,8:ftp,9:http) inpstr3-type =off # (0:off,1:serial,2:file,3:tcpsvr,4:tcpcli,7:ntripcli,8:ftp,9:http) inpstr1-path =ttyACM0:115200:8:n:1:off inpstr2-path =rtk2go.com:2101/[MountID] inpstr3-path = inpstr1-format =ubx # (0:rtcm2,1:rtcm3,2:oem4,3:oem3,4:ubx,5:ss2,6:hemis,7:skytraq,8:sp3) inpstr2-format =ubx # (0:rtcm2,1:rtcm3,2:oem4,3:oem3,4:ubx,5:ss2,6:hemis,7:skytraq,8:sp3) inpstr3-format =rtcm3 # (0:rtcm2,1:rtcm3,2:oem4,3:oem3,4:ubx,5:ss2,6:hemis,7:skytraq,8:sp3) inpstr2-nmeareq =off # (0:off,1:latlon,2:single) inpstr2-nmealat = # (deg) inpstr2-nmealon = # (deg) outstr1-type =tcpsvr # (0:off,1:serial,2:file,3:tcpsvr,4:tcpcli,6:ntripsvr) outstr2-type =file # (0:off,1:serial,2:file,3:tcpsvr,4:tcpcli,6:ntripsvr) outstr1-path =:52001 outstr2-path =/home/pi/RTKLIB/rtklog/%Y%m%d_%h%M_sol.pos outstr1-format =enu # (0:llh,1:xyz,2:enu,3:nmea) outstr2-format =llh # (0:llh,1:xyz,2:enu,3:nmea) logstr1-type =off # (0:off,1:serial,2:file,3:tcpsvr,4:tcpcli,6:ntripsvr) logstr2-type =off # (0:off,1:serial,2:file,3:tcpsvr,4:tcpcli,6:ntripsvr) logstr3-type =off # (0:off,1:serial,2:file,3:tcpsvr,4:tcpcli,6:ntripsvr) logstr1-path =/home/pi/RTKLIB/rtklog/%Y%m%d%h%M_rov.log logstr2-path =/home/pi/RTKLIB/rtklog/%Y%m%d%h%M_base.log logstr3-path =cor_%Y%m%d%h%M.log misc-svrcycle =10 # (ms) misc-timeout =20000 # (ms) misc-reconnect =20000 # (ms) misc-nmeacycle =5000 # (ms) misc-buffsize =32768 # (bytes) misc-navmsgsel =all # (0:all,1:rover,1:base,2:corr) misc-startcmd =./rtkstart.sh misc-stopcmd =./rtkshut.sh file-cmdfile1 =../../../data/ubx_m8p_rov_bds_5hz.cmd file-cmdfile2 =../../../data/ubx_m8p_ref_bds_1hz.cmd file-cmdfile3 = pos1-posmode =kinematic # (0:single,1:dgps,2:kinematic,3:static,4:movingbase,5:fixed,6:ppp-kine,7:ppp-static) pos1-frequency =l1 # (1:l1,2:l1+l2,3:l1+l2+l5) pos1-soltype =forward # (0:forward,1:backward,2:combined) pos1-elmask =15 # (deg) pos1-snrmask_L1 =40,40,40,40,40,40,40,40,40 # (dBHz) pos1-dynamics =off # (0:off,1:on) pos1-tidecorr =off # (0:off,1:on) pos1-ionoopt =brdc # (0:off,1:brdc,2:sbas,3:dual-freq,4:est-stec) pos1-tropopt =saas # (0:off,1:saas,2:sbas,3:est-ztd,4:est-ztdgrad) pos1-sateph =brdc # (0:brdc,1:precise,2:brdc+sbas,3:brdc+ssrapc,4:brdc+ssrcom) pos1-exclsats =C02 # (prn ...) pos1-navsys =49 # 49 (1:gps+2:sbas+4:glo+8:gal+16:qzs+32:comp) pos2-armode =fix-and-hold # (0:off,1:continuous,2:instantaneous,3:fix-and-hold) pos2-gloarmode =off # (0:off,1:on,2:autocal) pos2-bdsarmode =on pos2-arthres =3 pos2-arthres1 =0.9999 pos2-arthres2 =0.25 pos2-arthres3 =0.1 pos2-arthres4 =0.05 pos2-arlockcnt =0 pos2-arelmask =0 # (deg) pos2-aroutcnt =5 pos2-arminfix =10 pos2-slipthres =0.05 # (m) pos2-maxage =30 # (s) pos2-rejionno =30 # (m) pos2-niter =1 pos2-baselen =0 # (m) pos2-basesig =0 # (m) out-solformat =llh # (0:llh,1:xyz,2:enu,3:nmea) out-outhead =off # (0:off,1:on) out-outopt =off # (0:off,1:on) out-timesys =gpst # (0:gpst,1:utc,2:jst) out-timeform =tow # (0:tow,1:hms) out-timendec =3 out-degform =deg # (0:deg,1:dms) out-fieldsep = out-height =geodetic # (0:ellipsoidal,1:geodetic) out-geoid =internal # (0:internal,1:egm96,2:egm08_2.5,3:egm08_1,4:gsi2000) out-solstatic =all # (0:all,1:single) out-nmeaintv1 =0 # (s) out-nmeaintv2 =0 # (s) out-outstat =off # (0:off,1:state,2:residual) stats-errratio =100 stats-errphase =0.003 # (m) stats-errphaseel =0.003 # (m) stats-errphasebl =0 # (m/10km) stats-errdoppler =1 # (Hz) stats-stdbias =30 # (m) stats-stdiono =0.03 # (m) stats-stdtrop =0.3 # (m) stats-prnaccelh =1 # (m/s^2) stats-prnaccelv =0.1 # (m/s^2) stats-prnbias =0.0001 # (m) stats-prniono =0.001 # (m) stats-prntrop =0.0001 # (m) stats-clkstab =5e-12 # (s/s) ant1-postype =llh # (0:llh,1:xyz,2:single,3:posfile,4:rinexhead,5:rtcm) ant1-pos1 =0 # (deg|m) ant1-pos2 =0 # (deg|m) ant1-pos3 =0 # (m|m) ant1-anttype = ant1-antdele =0 # (m) ant1-antdeln =0 # (m) ant1-antdelu =0 # (m) ant2-postype =llh # (0:llh,1:xyz,2:single,3:posfile,4:rinexhead,5:rtcm) ant2-pos1 =34.xxxxx # (deg|m) ant2-pos2 =136.xxxxx # (deg|m) ant2-pos3 =xx.xxx # (m|m) ant2-anttype = ant2-antdele =0 # (m) ant2-antdeln =0 # (m) ant2-antdelu =0 # (m) misc-timeinterp =off # (0:off,1:on) misc-sbasatsel =0 # (0:all) file-satantfile =../../../data/igs05.atx file-rcvantfile =../../../data/igs05.atx file-staposfile =../../../data/station.pos file-geoidfile = file-dcbfile =../../../data/P1C1_ALL.DCB file-tempdir =../../../data/temp file-geexefile = file-solstatfile = file-tracefile = ``` Please create an executable file and give it execute permission ```shell= #!/bin/sh cd /home/pi/RTKLIB/app/rtkrcv/gcc/ ./rtkrcv -o /home/pi/RTKLIB/app/rtkrcv/my.conf -s -d /dev/tty0 ``` Also be prepared to start automatically (At this time, it will not work without -d / dev / tty0) # Translation of special site(14th line) From 第2回　キットが手元に届いたら + Check the componets of the product When the kit arrives, first check the product. Contains receiver and antenna. ![](https://i.imgur.com/6NSvNGF.png) (1) Receiver The base station TG-RTKA has NEO-M8P-2-10 and the mobile station TGRTK-B has NEO-M8P-0-10. Please check if it is correct. The antenna terminal is SMA-J. There is another micro USB terminal from which power is supplied to the receiver and connected to a personal computer. Holes for pin headers are provided on both sides of the board so that they can be connected to each terminal of the M8P module. One UART can be used by setting up a pin header. (The UART pin can be used as SPI by setting) For details, see the link of "Other technical resources" on the bottom right of the M8P product site below. For example, in the NEO-M8P Hardware Integration Manual, you can check the pin assignment of the NEO-M8P module. https://www.u-blox.com/ja/product/neo-m8p-series I used a 3D printer to make the case because I was afraid to use it as a board. Anything is fine, but it is safer to put it in a case. ![](https://i.imgur.com/COPepTg.jpg) (2) Antenna Antenna cable is less than 3m (slightly less than 3m). The back of the antenna is a magnet and can be used by attaching it to the roof of a car. The terminal is SMA-P at the end of the 3m cable and can be connected to the receiver as it is. This antenna is for GPS reception and drops about 5dBHz in BeiDou reception, but there is no problem in understanding and using it as a first step. First, please receive using this antenna. + Prepare what we need (1) Power supply / PC connection cable Prepare a micro USB cable to supply power to the receiver and connect to the computer. ![](https://i.imgur.com/VhtZ3gb.jpg) (2) Antenna ground plane Performance is not obtained with the antenna alone. Except when attaching to a conductor surface with an area of about 10 cm, such as mounting on a car roof, be sure to attach a ground plane . Without this, RTK will not perform well. I also bought a pot lid at a 100 yen shop. It is Φ185mm made of stainless steel. ![](https://i.imgur.com/SfIymyt.png) Please remove this handle and attach the antenna. ![](https://i.imgur.com/eu4esUW.jpg) like this (3) PC (Windows) Please use a Windows PC to run the u-blox M8P software installed on the receiver. Set by connecting with USB terminal. + Connecting ![](https://i.imgur.com/YrxUqds.png) グランドプレーン＝ground plane? なべぶた＝lid アンテナ＝antenna 受信機＝receiver マイクロ＝micro ![](https://i.imgur.com/FAiDXKI.jpg) + Install the antenna Next, check the operation. Let's receive the signal from the satellite. Please move to the window first (preferably the south side window where BeiDou satellite is easy to receive). Please get the antenna out of the window. Be careful not to drop the antenna or ground plane. If the antenna cannot be put out outdoors due to circumstances, its operation can be checked by placing it near a window, although the reception sensitivity is low. However, the receiving sensitivity is low and there are few satellites that can be received. It is cold season, but the outdoors are still the best. Ideally, it should be attached to the roof of a car, moved to a suburb where there are few buildings and trees around, or tried on the roof. I put the antenna outside the window. ![](https://i.imgur.com/15U0qx4.jpg) + Start u-center Please start u-cennter on your PC. The following screen will be displayed. ![](https://i.imgur.com/srIr5Kg.png) + Connect receiver to u-center To connect the receiver, select the connected COM. Select from the menu, Receiver> Port and select the connected COM number. Clicking the button below will do the same. ![](https://i.imgur.com/G23KMZi.png) (Supplement 1) What to do if the receiver does not appear on the port in Windows 10 Readers using Windows 10 may not find the COM connected to the receiver. This is because the receiver is recognized as another type of device. Please refer to the solution in the column of p.81 in the January 2018 issue. (In Device Manager, right-click the u-blox GNSS Location Sensor in "Sensor" and select Update Driver. Click "Choose from a list of available drivers on my computer" at the bottom and select "USB Serial Device", then "u-blox" in "Ports (COM and LPT)" "Virtual COM Port" appears. This is the solution.) (Supplement 2) What to do if settings are not reflected in u-center In subsequent u-center operations, settings may not be reflected or items may not be selectable from the pull-down menu. In this case, please insert and remove the USB several times and operate again. It may be recovered by repeating several times. If that doesn't work, repeat the following "Reset receiver settings to initial state" several times. After that, by closing and restarting u-center, this problem is often solved. The button turns green when connected. ![](https://i.imgur.com/vcZW6PY.png) You can know if u-center connected to the receiver by looking at the status display at the bottom right of the window. ![](https://i.imgur.com/8F5aybu.png) If the icon on the left side of the second connection of COM17 from the left is blinking green, connection is established. If this icon does not change, you have not connected to the receiver. Check the connected COM number of the receiver. From now on, let's proceed with the setting by looking at only the red letters. It is okay to skip the confirmation only item. There are not many setting items. Let's get started! + Reset receiver settings to default The next operation is to change the receiver settings. Readers who have already changed the settings may not be as described. Then, reset the receiver settings to the initial state. From the menu, select View> Configuration View. Then the Configuration window will be launched. ![](https://i.imgur.com/Tp2tOT2.png) Select CFG from the list on the right. Next, select "Revert to default Configuration" for the check box on the right side, select all the four nonvolatile memories of Divices, and "send". The settings have now been returned to the initial state. + Displaying reception status Let's display the reception status. Select the following display. 1) View menu> Docking Windows> Satellite Position 2) View menu> Docking Windows> Satellite Level 3) View menu> Docking Windows> Satellite Level History 4) View menu> Docking Windows> Data Please adjust the size of each view window. ![](https://i.imgur.com/xdpdWYx.png) The reception status was displayed like this. (1) Satellite Position: plotting Satellite position (elevation and azimuth) viewed from current location (2) Satellite Level: Displays the receiving sensitivity C / N0 of each satellite (3) Satellite Level History: Displays the transition of the receiving sensitivity of each satellite (4) Data: Display latitude, longitude, ellipsoid height, positioning flag, etc. The positioning flags indicate 3D (independent positioning), 3D / DGNSS (differential positioning), 3D / DGNSS / FLOAT (RTK positioning (FLOAT)), and 3D / DGNSS / FIXED (RTK positioning (FIX)). As can be seen from Satellite Level History and Satellite Position, the shipping status of the receiver is GPS + GLONASS reception. In the RTK using M8P, the fix solution can be obtained in a short time by the combination of GPS + BeiDou, so switch to GPS + BeiDou at u-center. + Switching the receiving satellite Switch from GPS + GLONASS reception to GPS + BeiDou reception. From the menu, select View> Configuration View. Then the Configuration window will be launched. ![](https://i.imgur.com/ucoM1iu.png) Select GNSS from the list on the left. Next, uncheck Enable for GLONASS on the right and check "Enable" for BeiDou. Whether or not the check of QZSS is checked, it does not yet support RTK positioning calculation inside the receiver module, but please check it. Finally, send. Then write this setting to the receiver module so that it will remain after a restart of the receiver. ![](https://i.imgur.com/IsyW2On.png) Select CFG from the list on the right. Next, select the "Save Current Configuration" check box on the right side, select all the four nonvolatile memories of Divices, and "send". (In order to return to the initial state at the beginning of the setting change, "Revert to default Configuration" was selected, but if you press the send button as it is, it will return to the initial state. Please be careful.) Your settings are now saved. (The operation to save this setting change will be used frequently in the future.) Check the screen of u-center. Is GLONASS switched to BeiDou and reception started? ![](https://i.imgur.com/24wrxYz.png) BeiDou reception does not start.There is a cause for this. Currently, BeiDou reception information is not supported in NMEA format in u-blox M8. Therefore, if UBX-format NAV-SVINFO data is not output, reception cannot be obtained and cannot be displayed. Therefore, this information is output. ![](https://i.imgur.com/1uTFhUl.png) Select MSG in the list on the right. Next, select NAV-SVINFO from the pull-down list of Message on the left and check USB. Finally, send. Then, to save the data in the non-volatile memory of the receiver module, perform the save operation in CFG as described above. I think the display of BeiDou has started. ![](https://i.imgur.com/UHtQ3Yu.png) It should be safe to turn off the receiver. Once, please plug and unplug the USB and check if GNSS is not changed and returned to GLONASS. If GLONASS is received, the change has not been reflected. + Let's set up RTK Now start setting up the RTK. I think that it was confirmed that the runaway of the positioning result was several meters in single positioning. When this is fixed with RTK, it becomes several cm. However, this is limited to the case where there is an open reference station within 10 km from the reader's residence. If it is more than that, Fix solution cannot be obtained. In the case of the FLOAT solution, in a few meters to several tens of cm, the positioning result wanders around to move to the Fix solution. Let's check that. Let's continue the following operations with u-center. From the menu, select View> Configuration View to launch the Configuration window. (1) DGNSS setting (confirmation only) ![](https://i.imgur.com/4LPJF1o.png) Select DGNSS in the list on the right. Next, make sure that the pull-down list of "Differential Mode" on the left is selected as "3-RTK fixed ambiguities are fixed whenever possible". If not, send it after the change.This setting is to find the integer bias (wave number between satellite and receiver antenna) in the process of finding the Fix solution. Use this setting if the distance from the reference station (called the base line length) is within 10 km. If the distance is longer than that, there is a possibility that a wrong fix will result in a wrong wave number even if a fix solution is obtained. Also, there is a phenomenon that the value of the positioning result skips in the process of finding the Fix solution. If you want to avoid this ski, select the following 2-RTK float. If you select this, you will not be fixed with Float, but you can avoid skipping the positioning value and fixing when fixing. ![](https://i.imgur.com/2Cd7o4S.png) This time it is operation check, so be prepared for mistake Fix and select 3-RTK fix. (2)Portの設定（確認のみ） ![](https://i.imgur.com/Rq1Xhvj.png) 右側リストのPRTを選択して下さい．次に左側のTarget のプルダウンリストで3-USBを選択して下さい．Protocol in, Protocol out がともに 0+1+5 UBX+NMEA+RTCM3に選択されていることを確認して下さい．If not, "send" it after the change. This setting specifies the input / output protocol for each port. For example, if you change "Protocol in" to 1 + 5 UBX + RTCM3, NMEA input from USB to receiver will be ignored. If you select UART1 as the "target", you can limit the input / output protocol of UART1. (3) MSG setting (only for confirmation) ![](https://i.imgur.com/nXSjtJ4.png) Select MSG in the list on the right. Next, select F0-00 NMEA GxGGA from the pull-down list of Message on the left. Make sure that USB is checked. If not, please check and "Send". The output to other interfaces I2C, UART1, and SPI is also set here. It is unnecessary, but does not need to be unchecked. The following data is output in the initial state. NMEA GxGGA NMEA GxGLL NMEA GxGSA NMEA GxGSV NMEA GxRMC NMEA GxVTG Of these, other than GxGGA is unnecessary. GxGSV adds SVINFO to the above operation (switching to BeiDou reception), but this data can also be used. SVINFO data sends more detailed data than GxGSV, and you can display more detailed reception status. GxGLL, GxGSA, GxGSV, GxRMC, GxVTG may be cut by USB output setting (either is acceptable). (Supplement) What does x in GxGGA stand for? The first two characters are called the Talker ID. Talker ID was GP like GPGGA in the age of GPS only. After that, GL (GLONASS), GN (complex satellite system), GB (BeiDou), GA (Galileo), etc. are defined. When updating the receiver in the GPS age, if there is a system that can not receive unless the Talker ID is GP, this change will be a problem. In u-center and RTKLIB, this Talker ID can be selected. (4) TMODE3 setting (confirmation only) ![](https://i.imgur.com/qjyEFDZ.png) Select TMODE3 in the list on the right. Next, check that "0-Disabled" is selected from the "Mode" pull-down list on the left. (Hereafter, this section explains how to install the base station on your own. There is no operation required for this operation check.) Use this setting when setting the base station (related to what is called the My base station in the January 2018 issue). If you select 1-Survey in, you can enter Survey in. This mode is for averaging the positioning results of independent positioning and automatically setting them to the base station coordinate values. Set the minimum observation time and required positioning accuracy. For example, if the minimum observation time is set to 300 seconds and the required positioning accuracy is set to 5 m, observation will be performed for 300 seconds or more. If the distance is more than 5m, continue to observe and the coordinate value of the base station will not be determined until it is within 5m. (5) Change NAV5 settings ![](https://i.imgur.com/q3Me5Zd.png) (5) Select NAV5 in the list on the right. Next, make sure that "0-Portable" is selected from the "Dynamic Mode" pull-down list on the left. For automatic car use, it is better to select "4-AutoMotive" ("0-Portable" doesn't cause any problems, it just doesn't get the best performance).Next, change the minimum elevation angle of the satellite to be received from 10 [deg] to 15 [deg]. Signals from low-elevation satellites are noisy because their paths are long and contain many multipaths. Even if you don't work hard, it is safer to use a high quality satellite with a high elevation angle, so raise the elevation angle. I would like to raise it further, but this will reduce the number of receiving satellites, so please balance it. Finally, set the threshold of the receiving sensitivity. Set to 35 [dBHz] in consideration of the receiving sensitivity of the attached antenna. (If using a high-performance antenna, adjust the number of satellites to a value that can receive at least about 10 satellites. It is about 40 to 42 [dBHz]). Finally, "send". (6) Change NMEA settings ![](https://i.imgur.com/ZhxKySL.png) Select NMEA in the list on the right. Next, select CFG-NMEA-DATA2 from the pull-down list on the upper left side. Check "High Precision Mode" of "Mode Flags".This setting corresponds to the lack of RTK precision in the representation with the normal format digits of GxGGA. With this setting, positioning results can be output up to the number of millimeter digits.Finally, "send". Send the settings in CFG to save the settings in nonvolatile memory.If you forget this, the settings will be lost when the power is turned off.Be careful! (7) Ntrip Client settings Receives RTK base station data. Connect your PC to the network. If the port does not pass due to security reasons such as inside a company, Ntrip data cannot be received. In that case, please receive by tethering or mobile router. Reception can be sufficiently performed in low-speed mode of bargain SIM, but reception is affected on low-quality lines where data clogging frequently occurs. Be careful. Then do the following operations with u-center. From the menu, select Receiver> NTRIP Client ... to launch the NTRIP client settings window. ![](https://i.imgur.com/JTM6Uly.png) Enter the base station information distributed from NTRIP Caster here. Here, we will receive a reference station registered as an open reference station at Ibaraki National College of Technology. Enter the following values in Address, Port, Username, Password in NTRIP Caster Settings. -Address 52.185.144.65 -Port 2102 -Username ibaraki -Password kousen Then press the button of Update source table. Then, Iba-RAW and Iba-RTCM3 will appear at Ntrip Mount Point. Of these, select Iba-RTCM3. Finally, click the OK button. In addition to the above, the reference stations of University of Tsukuba, Shizuoka University and CQ Publishing are available. In addition, please select the connection destination that is short distance. RTK starts when receiving the base station data from Ntrip Caster. Looking at the Data window, the Fix Mode changes from 3D to 3D / DGNSS / FLOAT, and the convergence of the solution begins with the aim of the Fix solution. If the distance from the reference station is as short as about 10 km, the wave number is accurately determined and changes to 3D / DGNSS / Fixd. At this time, the accuracy is several cm. ![](https://i.imgur.com/aPCMSJy.png) + (7) Plotting to "MAP" Let's check the status in "Map View". The View menu> Docking Windows> Map View displays a screen where positioning results are plotted on a digital map. Please adjust the size. The green point is the positioning result history and the yellow point is the current result. It's a bit hard to see (you can change the shape of the plot to a cross (x). Right-click and look for it in the menu). I think that you can compare the positioning results of the single positioning because it is also plotted. ![](https://i.imgur.com/Gcp8llU.jpg) There is no accuracy near the window. Please try it in an open place. The accuracy of fixing correctly is excellent. I think many readers feel that it does not match the map. This map was created at the accuracy level of the differential method, and the accuracy is about 50cm-1m at the highest. RTK is always more accurate. If the coordinate values of the base station are well-measured, the accuracy of the RTK positioning result is not bad, but the accuracy of the map is bad. There is often a consultation that accuracy may be poor because it does not match the map, but please note that it is easy to misunderstand. Conversely, the idea of being accurate because it fits perfectly with the map is also dangerous. + Data flow in RTK In this RTK, what kind of data flow and where is the positioning calculation performed? The following figure shows the outline. ![](https://i.imgur.com/GYjtyTA.png) アンテナ＝antenna 受信機＝receiver 基準点＝reference point 測位計算エンジン＝Positioning calculation engine 測位結果＝Positioning result モバイルルータ＝mobile router Ntrip Clientとしてアクセス＝access as Ntrip Client Everybody accesses Ntrip Caster from u-center on Windows and receives the base station data (RTCM3) of one of the base stations connected to it (this time, the base station of Ibaraki National College of Technology). The data is sent to the receiver, and positioning is calculated using the positioning calculation engine inside the receiver. The result is returned to the personal computer (GxGGA) and displayed on u-center. Next is the contents of RTCM3. RTCM3 shows the message type by four digits after Message Type. Please refer to this:https://www.use-snip.com/kb/knowledge-base/rtcm-3-message-list/. In case of GPS + BeiDou in M8P, RTCM3 contains the following signals. -RTCM3 Type 1005 base station coordinate value -Pseudorange, carrier phase, and Doppler of RTCM3 Type 1077 GPS. Signal strength -RTCM3 Type 1127 BeiDou pseudorange, carrier phase, Doppler. Signal strength GPS (L1) and BeiDou (B1) are less than 3,000bps.