GRTK User Manual

System Introduction

Introduction

GRTK is a dual-antenna high-precision differential positioning and directional module (Real Time Kinematics) independently developed by Blicube. A complete RTK system can be formed through two GRTK modules (one mobile terminal and one base station terminal).

The module is based on a new generation of high-performance GNSS SoC chip design,supports multi-system multi-frequency RTK positioning, supports dual-antenna high-precision orientation, and supports GPS&GLONASS&Beidou&Galileo&QZSS navigation and positioning. It is mainly for high-precision positioning and orientation requirements such as drones, robots and intelligent driving.

Figure 1.1 Physical image of GRTK centimeter-level positioning and orientation system

Parameters

  • Performance
Frequencies BDS B1I/B2I1
GPS L1/L2
GLONASS L1/L2
Galileo E1/E5b
QZSS L1/L2
Single Point Positioning (RMS) Horizontal:1.5m
Vertical:2.5m
DGPS (RMS) Horizontal:0.4m
Vertical:0.8m
RTK (RMS) Horizontal:1cm+1ppm
Vertical:1.5cm+1ppm
Heading Accuracy (RMS) 0.2 degree/1 m baseline
Velocity Accuracy (RMS) 0.03 m/s
Time Accuracy (RMS) 20 ns
Time to First Fix (TTFF) Cold start < 25 s
Initialization Time < 5s (typical)
Reacquisition < 1 s
Correction RTCM v2.3/3.0/3.2
Data Output NMEA-0183
Update Rate 20 Hz
Inertial Navigation Accuracy < 5% of distance travelled during GPS denied conditions
Working Temperature -20℃ to +85℃
Power Supply 5v to 35v
  • Physical size
Figure 1.2 Schematic diagram of physical size

Usage

Interfaces

The GRTK module can be used as a base station or as a mobile station. There are three interfaces in total, as shown in Figure 2.1. They are the Power port for powering the device, the com1 port for communication between the mobile station and the base station, and the com2 port for communicating with the flight controller to transmit positioning information. The com2 port includes uart2 and uart3, and the default use of uart2 is the serial port of flight control communication.

Figure 2.1 GRTK module interfaces diagram

In addition, there are four LED indicators on the front of the module. The three on the left display the module’s operating status, which are 3D Fix positioning status, operating error, and RTK positioning status; a single indicator on the right is used to display the power supply status.

The GRTK module supports dual antenna direction finding, where the left antenna(ANT1) is the master antenna, the right antenna(ANT2) is the slave antenna, and the single antenna needs to be connected to the master antenna.

Hardware connection

  • Base station connection
Figure 2.2 Base station connection diagram
Figure 2.3 Schematic diagram of base station tripod installation
  • Rover connection
Figure 2.4 Rover connection diagram
  • Dual-antenna rover connection
Figure 2.5 Dual antenna rover connection diagram

When the base station is not used, only the rover can be used as a conventional positioning device for positioning. The connection is shown in Figure 2.3.

The base station and the rover can be used together to form an RTK centimeter-level positioning system, and the base station supports plug and play.

The dual-antenna direction finding of the rover needs to keep the master-slave antenna consistent with the heading in accordance with the master-back-and-forward. The distance between the master-slave antennas should be greater than 30cm to ensure the direction finding accuracy.

Indicator light & Positioning status

There are 4 indicators on the GRTK module, the specific meanings are shown in the table below:

Light Status Describe
FIX On
Off
Enter 3D Fixed state.
Not in 3D Fixed state.
ERR On
Off
Error! The module does not work properly.
No error has occurred and is working properly.
RTK On
Off
Enter RTK Fixed state.
Not in RTK Fixed state.
PWR On
Off
The power supply is OK.
The power supply is abnormal.
  • When the Base is working properly, the status of lights :
    • PWR and FIX are on,the other lights are off.
  • When the Rover is working properly, there are two conditions in which the status of lights :
    • PWR and FIX are on,the other lights are off, that means Rover has been in 3D Fixed state.
    • PWR, FIX and RTK are on, the other lights are off, that means Rover has been in RTK Fixed state.

Positioning data description

The GRTK module outputs NMEA protocol positioning data by default, connects computer with GRTK module’s Tx2 and Rx2 by USB-to-TTL module, then you can use the serial assistant to read or configure the output message.

GRTK Rover and Base are factory configured, non-professionals do not configure equipment at will.PS: Please set the line break to CR&LF.

Rover with a single antenna

  • Output messages at 5Hz by factory default:
$GPGGA: Global positioning system fix data
$GPRMC: Recommended minimum data
$GPHDT: Output current heading information
$KSXT: Time, positioning and heading of GNSS receiver
  • Other message

If needed, you can send ASCII syntax by serial port to configurate it:

Configuration Format: GPXXX COMX XX(message + output port + output rate)
SAVECONFIG(Save configuration)
  • Reset

If output message is inconsistent with the factory during use, the output can be reset by following commands:

FRESET
GPGGA COM2 0.2  
GPRMC COM2 0.2  
GPHDT COM2 0.2  
KSXT COM2 0.2
SAVECONFIG
(PS:CR&LF here)

Rover with dual antennas for heading

  • Output messages at 5Hz by factory default:
$GPGGA: Global positioning system fix data
$GPRMC: Recommended minimum data
$GPHDT: Output current heading information
$KSXT: Time, positioning and heading of GNSS receiver
  • Other message

If needed, you can send ASCII syntax by serial port to configurate it:

Configuration Format: GPXXX COMX XX(message + output port + output rate)
SAVECONFIG(Save configuration)
  • Reset

If output message is inconsistent with the factory during use, the output can be reset by following commands:

FRESET
GPGGA COM2 0.2  
GPRMC COM2 0.2  
GPHDT COM2 0.2  
KSXT COM2 0.2
SAVECONFIG
(PS:CR&LF here)

Guidance for Use

The current version of the GRTK cm positioning system supports the output of NMEA protocol positioning data, the following guidance is based on the Ardupilot firmware(v4.2.0 or higher) using the Mission Planer ground station.

Connection for modules

  • Have the hardware, including Pixhawk controller, GRTK, radio, battery, etc, shown in Figure 3.1 ready for connection before wiring:
Figure 3.1 Hardware physical diagram
  • Rover Base and data transmissions need to be supplied separately.

The communication mode between Rover and Base

GRTK can achieve RTK positioning by communicating through independent links between the base station and the rover station or by forwarding the base station data by the ground station.

  • Independent link
    • Please connect the COM2 port of the GRTK Rover to the GPS port of Pixhawk and the com1 port to connect the data transmission device that communicates with the Base sideb) Please connect the GRTK Base com1 port to the computer through the serial port
    • Connect antenna to the GRTK Base and connect the com1 port of the base side to the data transmission device that communicates with the Rover terminal.
  • Forwarding the base station data by the ground station
  1. Please connect the COM2 port of the GRTK Rover to the GPS port of Pixhawk.
  2. Connect the GRTK Base com1 port to the computer through the serial port.
  3. Open Mission Planner, find the Optional Hardware at the Initial Setup, and select RTK/GPS Inject.

4. Choose the correct com port and click Connect.

5. Wait for about one minute for Base to complete the base station positioning, at this time the red in the RTCM column turns green, and the latitude and longitude information of the current base station is displayed, that is, the ground station has been realized to forward the Base positioning data

Mission Planner settings

GRTK Base supports plug-and-play and does not require additional setup at the ground station. However, before actually using RTK, you need to set the parameters for flight control in MP, and the necessary parameter settings are given below, which can be referred to as follows:

https://ardupilot.org/copter/docs/common-gps-for-yaw.html

  • Configure the GPS protocol as NMEA and set the GPS data refresh rate to 5Hz.
    • GPS_TYPE is set to 5 to configure the GPS protocol as NMEA.
    • GPS_RATE_MS is set to 200ms which means the GPS data refresh rate is 5Hz.
  • GPS direction needs to be enabled using dual antenna direction measurement.
    • AHRS_EKF_TYPE is set to 3 to choose EKF3.
    • EK2_ENABLE is set to 0 to disable EKF2.
    • EK3_ENABLE is set to 1 to enable EKF3.
    • EK3_MAG_CAL is set to 5 to enable GPS direction.
    • EK3_SRC1_YAW is set to 2 to GPS.

Positioning testing

  • Use Rover to draw a basketball court line by following the real line.
Figure 3.4 GRTK test result
  • Unmanned vehicle automatic route mission measurement.
Figure 3.5 GRTK auto-mission control test result

Modes of Base Station

GRTK Base has two modes of operation,self-optimizing base station and fixed base station.

  • Self-optimizing base stationWhen it is not clear exactly where the base station will be located, Base will position itself and average itself for a certain period of time after installation as the coordinates of the base station.
  • Fixed base station: When know the exact coordinates of the base station location will be set up, you need to enter that exact coordinate into the base station.

Self-optimizing base station

  • Base station default operating mode is self-optimizing base station. Using USB to TTL module to connect the base station serial 2 (Rx2&Tx2) to the computer, the computer runs serial debugging assistant, open the corresponding serial port with the baud rate of 115200. The base station returns the current location information.
  • Send the following command (PS: Commands need to end with a line break) to base station by serial to complete configuration.
  • mode base time 60 1.5 2.5

Within 60-second automatic positioning of the base station, or when the standard deviation of horizontal positioning is no more than 1.5 m and that of vertical positioning is no more than 2.5 m, set the average value of horizontal and vertical positioning results as the base station coordinates. Restarting the base station triggers a new calculation and reposition of the datum coordinates. Users can modify parameters according to their needs.

  • After configuration, send the following command (PS: Commands need to end with a line break) to base station by serial to save configuration.
  • saveconfig

Fixed base station

Fixed base station mode configuration is divided into two steps, the first step is to obtain the current exact coordinates, the second step is to enter the base station’s precise coordinates into the base station.

Step1: Get the current exact coordinates

Using the USB-to-TTL module to connect the base station serial 2 to the computer, the computer runs the serial debugging assistant, open the corresponding serial port, Baud rate of 115200. The base station returns the current location information.

  • Send the following command (PS: Commands need to end with a line break) to base station by serial to complete configuration.
  • mode base time 60 1.5 2.5

Within 60-second automatic positioning of the base station, or when the standard deviation of horizontal positioning is no more than 1.5 m and that of vertical positioning is no more than 2.5 m, set the average value of horizontal and vertical positioning results as the base station coordinates. Restarting the base station triggers a new calculation and reposition of the datum coordinates. Users can modify parameters according to their needs.

Note that the obtained WGS84 coordinates indicate that the base station initialization is complete when the data is stable.

Step2: Enter the exact coordinates of the base station into the base station

  • Copy the location information of the base station output

#BESTPOSA,COM2,0,91.0,FINE,2164,52077.000,420887,32,18;SOL_COMPUTED,FIXEDPOS,32.02245993006,118.85899391094,68.5505,2.0115,WGS84,0.0000,0.0000,0.0000,””,0.000,0.000,40,28,28,16,0,06,03,53*17b29c25 (Sample data)

  • Analyze and get longitude, latitude and elevation data

32.02245993006,118.85899391094,68.5505(Please replace it based on the actual measurement data

  • The configuration command is generated based on the exact coordinates of the base station

mode base 32.02245993006 118.85899391094 68.5505

Send the configuration command (note that the command needs to end with a line break) to the base station through a serial port.

  • When the configuration is complete, the following command (note that they need to end with a line break) is sent to the base station through a serial port to save the configuration.
  • saveconfig

Precautions

  • With our GRTK Kit, the base station side supports plug-and-play. If only Rover is purchased, the use of other companies’ base station end requires additional RTK base station configuration at the ground station, which does not guarantee compatibility and positioning accuracy.
  • This product is positioning equipment, which needs to search for satellite positioning, try to test it in the open and undisturbed site.
  • The positioning status of GRTK should be mainly decided by the ground station.

Purchase

Link for purchase

AliExpress: GRTK (BLI Store)

List

Express delivery

  • Appropriate logistics methods need to be adopted according to the actual situation.

Wholesale

  • Wholesale prices vary depending on the quantity of the wholesale, please contact customer service for more details.

Test videos

  1. Centimeter-level positioning accuracy test.
  2. The base station is quickly deployed within 30s.
  3. Stationary positioning test & drone light painting with GRTK.     

GRTK用户手册

系统介绍

系统简介

GRTK是blicube(北力电子)独立研发的双天线高精度差分定位定向模块(Real Time Kinematics),通过两个GRTK模块(一个移动端,一个基站端)可组成完整的RTK系统。

该模块基于新一代国产高性能GNSS SoC芯片设计,支持多系统多频点RTK定位,支持双天线高精度定向,支持北斗导航定位,主要面向无人机、机器人及智能驾驶等高精度定位定向需求。

图1.1 GRTK厘米级定位定向系统实物图

技术参数

  • 性能指标

项目  
频点 BDS B1I/B2I1 GPS L1/L2 GLONASS L1/L2 Galileo E1/E5b QZSS L1/L2
协议 NMEA-0183,RTCM
时间精度(RMS) 20ns
单点定位(RMS) 平面:1.5m 高程:2.5m
DGPS (RMS) 平面:0.4m 高程:0.8m
RTK (RMS) 平面:1cm+1ppm 高程:1.5cm+1ppm
定向精度(RMS) 0.2度/1m基线
速度精度(RMS) 0.03m/s
工作温度 -20℃到+85℃
工作电压 支持宽压输入:5v-35v
工作功耗 2.5W

  • 实物尺寸

图1.2 实物尺寸示意图

连接与使用

接口定义

GRTK模块既可以作为基站也可以作为移动站使用,共有三个接口,如图2.1所示。分别是用于设备供电的Power口,用于移动站和基站通信的com1口以及用于与飞控通信传输定位信息的com2口,其中com2口包含串口2和串口3,默认使用串口2作为与飞控通信的串口。

图2.1 GRTK模块接口图

另外,模块正面还有四个led指示灯,左侧三个显示模块运行状态,分别是3D Fix定位状态、运行错误和RTK定位状态;右侧单独一个指示灯用于显示供电状态。

GRTK模块支持双天线测向,其中左天线为主天线,右天线为从天线,单天线使用需连接主天线。

硬件连接

  • 基站(Base)端连线图

图2.2基站连线图

图2.3基站三脚架安装示例

  • 移动站(Rover)端连线图

图2.3移动站端连线图

  • 双天线移动站(Rover)端连线图

图2.4 双天线移动站端连线图

在不使用基站的时候,仅使用移动站也可以作为常规定位设备进行定位,接线如图2.3所示。

基站与移动站共同使用可组成RTK厘米级定位系统,基站支持即插即用。

移动站双天线测向需要将主从天线按照主后从前与航向保持一致,主从天线间距应大于30cm以保证测向精度。

指示灯&定位状态

    GRTK模块上共有4个指示灯,具体含义如下表所示:

以一套GRTK(基站+移动站)为例。

基站正常工作状态灯如下:

POWER灯和FIX灯常亮,其他灯不亮;

移动站正常工作状态一:

POWER灯和FIX灯常亮,其他灯不亮,移动站已进入标准3D单点定位;

移动站正常工作状态二:

POWER灯、FIX灯、RTK灯常亮,其他灯不亮,移动站已进入RTK固定解。

定位数据说明

GRTK模块默认输出NMEA协议定位数据,连接USB转TTL与GRTK模块com2的Tx2与Rx2,可利用串口助手读取或者配置输出语句。GRTK移动站和基站在出厂时均已配置,非专业人士请勿随意配置设备,另外推荐使用友善串口助手设置 换行为CR&LF 再进行输出语句的换行。

常用配置语句

freset

恢复出厂设置,注意:出厂设置的波特率为 115200.

config

查询接收机串口状态

config com1 115200

设置 com1 波特率为 115200
可以分别对 com1、com2、com3 设置为 9600, 19200,
38400, 57600, 115200, 230400,460800 中任意一个波特率

saveconfig

保存设置

单天线移动站

  • 出厂默认以5Hz速率输出语句:

$GPGGA: Global positioning system fix data
$GPRMC: Recommended minimum data
$GPHDT: Output current heading information
$KSXT: Time, positioning and heading of GNSS receiver

  • 配置语句

对于有其他语句信息需求的,可通过串口自行配置:

  1. GPXXX COMX XX(语句+com口输出数据+语句输出速率)
  2. SAVECONFIG(保存设置)
  3. 重置命令

如在配置或者使用过程中发现输出语句与出厂时不一致,可通过以下命令进行重置输出:

FRESET
GPGGA COM2 0.2  
GPRMC COM2 0.2  
GPHDT COM2 0.2  
KSXT COM2 0.2
SAVECONFIG
(PS:此处需要使用CR&LF换行)

双天线测向移动站

  • 出厂默认以5Hz速率输出语句:

$GPGGA: Global positioning system fix data
$GPRMC: Recommended minimum data
$GPHDT: Output current heading information
$KSXT: Time, positioning and heading of GNSS receiver

  • 配置语句

对于有其他语句信息需求的,可通过串口自行配置:

  1. GPXXX COMX XX(语句+com口输出数据+语句输出速率)
  2. SAVECONFIG(保存设置)
  3. 重置命令

如在配置或者使用过程中发现输出语句与出厂时不一致,可通过以下命令进行重置输出:

FRESET
GPGGA COM2 0.2  
GPRMC COM2 0.2  
GPHDT COM2 0.2  
KSXT COM2 0.2
SAVECONFIG
(PS:此处需要使用CR&LF换行)

使用教程

目前版本的GRTK厘米级定位系统,支持NMEA协议定位数据的输出,以下教程基于Ardupilot固件采用Mission Planner地面站进行操作说明。

设备接线

  • 请在接线前准备好如图3.1所示的硬件用于连接:

图3.1 硬件实物图

  • GRTK可以通过基站与移动站间通过独立链路通信或者地面站转发基站数据的两种方式实现RTK定位

独立链路方式下:

  1. 请将GRTK Rover的com2口连接到pixhawk的GPS口,com1口连接与Base端通信的数传设备。
  2. 请将GRTK Base进行天线连接和供电,并将com1口连接与Rover端通信的数传设备。

地面站转发基站数据方式下:

  1. 请将GRTK Rover的com2口连接到pixhawk的GPS口;
  2. 请将GRTK Base 上电,并将其com1口与电脑进行串口连接;
  3. 打开Mission Planner地面站,找到初始设置处的可选硬件,选择RTK/GPS Inject

d. 选择正确的com口,并点击Connect;

e. 等待大约一分钟Base完成基站定位,此时RTCM栏中的红色都变为绿色,且显示当前基站的经纬度信息,即已实现地面站转发Base定位数据。

PS:移动站、基站和数传需单独供电。

Mission Planner的设置

GRTK Base支持即插即用,不需要在地面站进行额外的设置。但在实际使用RTK之前,需要先在MP中对飞控进行参数设置,下面给出必须的参数设置(适配Ardupilot 固件v4.2.0或更高版本),具体可参考:

https://ardupilot.org/copter/docs/common-gps-for-yaw.html

1、配置GPS协议为NMEA,并将GPS数据刷新速率设置为5Hz(默认值)

参数列表:

  • GPS_TYPE 5   设置为NMEA输入
  • GPS_RATE_MS 设置为200ms,频率为5Hz

2、使用双天线测向需启用GPS航向

参数列表:

    • EK3_SRC1_YAW 设置为2,使用GPS提供航向

如需关闭磁罗盘:

  • COMPASS_ENABLE 设置为0

RTK定位实测

1、移动站篮球场框线绘制效果实测

图3.4 RTK实测效果图

2、无人车自动航线任务实测

图3.5 RTK自动航线任务效果图

基站两种工作模式

GRTK基站有两种工作模式,为自主优化设置基站模式和固定基站模式。自主优化设置基站:即在将架设基站的点没有精确坐标。可设置基站在安装点上进行一定时间内自定位取平均值,设置为基站的坐标。固定基站:即在将架设基站的点有精确坐标。需要将基站的精确坐标输入基站。

自主优化设置基站模式配置

GRTK基站默认工作模式是自主优化设置基站模式。配置方法如下:使用USB转TTL模块将基站的串口2连接到电脑,电脑运行串口调试助手,打开对应的串口,波特率为115200。基站返回当前的位置信息。

将如下的命令(注意命令需要以换行符结尾)通过串口发送给基站,完成配置。

mode base time 60 1.5 2.5

命令解释:基站自主定位60秒;或者水平定位标准差<=1.5m,且高程定位标准差<=2.5m时,把水平定位的平均值和高程定位的平均值作为基站坐标值。用户可以根据自己的需求修改参数。

配置完成后,将如下的命令(注意命令需要以换行符结尾)通过串口发送给基站,保存配置。

saveconfig

固定基站模式配置

固定基站模式配置分为两步,第一步获取当前的精确坐标,第二步将基站的精确坐标输入基站。

第一步 获取当前的精确坐标

使用USB转TTL模块将基站的串口2连接到电脑,电脑运行串口调试助手,打开对应的串口,波特率为115200。基站返回当前的位置信息。

       将如下的命令(注意命令需要以换行符结尾)通过串口发送给基站。

mode base time 60 1.5 2.5

命令解释:基站自主定位60秒;或者水平定位标准差<=1.5m,且高程定位标准差<=2.5m时,把水平定位的平均值和高程定位的平均值作为基准站坐标值。用户可以根据自己的需求修改参数。

观察获取到的WGS84坐标,当坐标稳定时,表示基站初始化完成。

复制基站输出的位置信息如下

#BESTPOSA,COM2,0,91.0,FINE,2164,52077.000,420887,32,18;SOL_COMPUTED,FIXEDPOS,32.02245993006,118.85899391094,68.5505,2.0115,WGS84,0.0000,0.0000,0.0000,"",0.000,0.000,40,28,28,16,0,06,03,53*17b29c25

获取经度纬度和高程数据如下

32.02245993006,118.85899391094,68.5505(这是示例数据,请根据实际测量数据进行替换)

第二步 将基站的精确坐标输入基站

根据基站的精确坐标生成配置命令

mode base 32.02245993006 118.85899391094 68.5505

将配置命令(注意命令需要以换行符结尾)通过串口发送给基站。

配置完成后,将如下的命令(注意命令需要以换行符结尾)通过串口发送给基站,保存配置。

saveconfig

注意事项

1、使用本公司RTK套装,基站端支持即插即用,如果仅购买了移动端,使用其他公司的基站端需要在地面站进行额外的RTK基站端配置,无法保证兼容性和定位精度。

2、本产品为定位设备,需要搜索卫星定位,使用时应尽量在空旷无干扰的场地测试。

3、RTK的定位状态需以地面站显示为主。

GRTK购买

1、购买地址

淘宝店铺:北力电子

2、发货清单

基站安装架
名称 数量 单位
底板 1
盖板 1
天线底板 1
45mm铝柱M3 8
8mm铝柱M3 12
M3x5螺钉 45
三脚架快拆铝板 1

GRTK模块
名称 型号 数量 单位
GRTK BASE 1
GRTK ROVER 1
多星多频GNSS天线 BL-320 3
分电板 标准 2
电源线 GH1.25 4P-GH1.25 4P(接分电板) 2
BASE端配线 GH1.25 5P-GH1.25 5P(接数传) 1
ROVER端配线 GH1.25 5P-GH1.25 5P(接数传) 1
GH1.25 6P-GH1.25 10P(接pixhawk控制器) 1
GH1.25 6P-杜邦头(用于配置GRTK) 1

图4-1  发货实拍图

3、物流

       本店国内默认顺丰包邮,国外客户需根据实际情况采取合适的物流方式。

4、关于批发

       根据批发数量的不同,批发价格不等,有批发需求请联系客服。

  • 视频

   测试视频一:

   绕操场全程,厘米级压线精度:

https://www.bilibili.com/video/BV1Bg411g7Sy

   测试视频二:

   GRTK30s快速部署基站

https://www.bilibili.com/video/BV1Kq4y1L7W8

   测试视频三:

   GRTK静止精度&无人机光绘:

https://www.bilibili.com/video/BV1iV411j7M8