LG69T (AM,AP) DR&RTK Application Note

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About the Document

Document Information

Revision History

Contents

About the Document

Contents

Table Index

Figure Index

1 Introduction

This document describes the dead reckoning (DR) and real-time kinematic (RTK) features, including orientation, mounting, calibration, and messages related to DR and RTK of Quectel LG69T (AM) and LG69T (AP). The supported features on each module are as follows:

• LG69T (AM) supports RTK only.
• LG69T (AP) supports DR and RTK.

The modules are recommended for use in four-wheel vehicle.

[Description of Figure 1: Four-Wheel Vehicle - A typical passenger car.]

1.1. Overview on DR

Quectel LG69T (AP) supports the ADR mode, where the module utilizes speed data from the vehicle and the onboard 6-axis sensor to enhance accuracy in environments without GNSS coverage. The module obtains vehicle speed data through CAN interface, supporting receiving data that conforms to ISO11898-1 standard. The vehicle speed requirement includes a minimum injection frequency of 10 Hz, delay below 10 ms, and speed RMS below 0.5 m/s.

1.2. Overview on RTK

Quectel offers high-precision RTK positioning products that support multiple GNSS constellations and frequencies, enabling centimeter-level accuracy. RTK (Real Time Kinematic) is a real-time differential GPS (RTDGPS) technology based on carrier phase observations. It consists of three components: a base station (which may be an actual satellite receiver or a virtual reference station (VRS), differential correction data link, and rover. The base station continuously observes GNSS satellites, and transmits its observation data and station information to the rover in real-time through a data transmission network. While receiving GNSS satellite signals, the rover uses the data transmitted by the base station through wireless receiving equipment to calculate its three-dimensional coordinates in real-time relative to the base station, using the principle of relative positioning.

[Description of Figure 2: RTK Schematic Diagram - Illustrates a base station (on a tripod) communicating with a rover (on a vehicle) via satellite signals and a data transmission network.]

2 Configuration

2.1. DR Configuration

2.1.1. Orientation

The LG69T (AP) modules are specifically designed for use in four-wheel vehicles. Module with GNSS and motion sensor ICs must be firmly and securely fixed to vehicle body. No relative movement is allowed between vehicle and device, and maximum isolation from both shock and vibration must be provided. Manually holding the board is not accepted. The recommended installation method is to firmly screw the device down to the vehicle frame. Mounting location should allow easy access to power supply and GNSS antenna, while avoiding exposure to excessive heat.

The reference frame axes definitions are as follows:

• The X-axis points towards the right side of the vehicle.
• The Y-axis points towards the front of the vehicle.
• The Z-axis points upwards from the vehicle.

[Description of Figure 3: Reference Frame - Shows a vehicle with a 3D coordinate system (X, Y, Z axes) indicating direction relative to the vehicle: X to the right, Y forward, Z upwards.]

2.1.2. Mounting

When mounting the Quectel LG69T (AP) module on the vehicle:

1. Firmly attach LG69T (AP) to the vehicle body, preferably as close to the center of the rear wheel as possible.
2. The default installation of LG69T (AP) should be horizontal, aligning the X/Y axis of the module with the X/Y axis of the vehicle body as closely as possible, and ensuring the misalignment angles (α, β, γ) are less than 10°.
3. Avoid misalignment angles (α, β, γ) greater than 30°.

[Description of Figure 4: IMU Reference Frame - Depicts a small rectangular module labeled LG69T with its internal X, Y, and Z axes shown.]

[Description of Figure 5: Installation Yaw Angle - Shows a car from above, illustrating the yaw misalignment angle (α) of the mounted module relative to the vehicle's longitudinal axis.]

2.1.3. DR Calibration

To ensure accurate functioning of the dead reckoning functionality, the module requires calibration. Follow the steps below for DR calibration:

1. Fix the module on the vehicle frame firmly. Any displacement, rotation or tilt of the device relative to the vehicle plane, however small, may cause performance issues and/or void calibration.
2. Calibration should be performed under good GNSS signal and clear sky conditions.
3. Power up the module, then start the vehicle on a plain surface.
4. Drive at a speed of more than 2.5 m/s, and preferably perform at least 1 turning movement. Then, the module will start self-calibration, which will be completed in 2 minutes.
5. Once the calibration process is completed, the module immediately outputs the $PQTMDRPVA message. See Chapter 4.2 PQTMDRPVA for details about the message.

After the calibration, there is no limit to driving trajectory and driving dynamics, and you can perform verification tests in the following scenarios:

1. Open sky area, urban main road (good satellite signal).
2. Urban tunnels (absence of satellite signal).
3. Urban viaduct (weak satellite signal).
4. Underground vehicle park (absence of satellite signal).
5. Areas surrounded with dense buildings (multi-path in urban canyon).
6. City boulevards (weak satellite signal).
7. High-rise dense area (severe urban canyon multipath).

[Description of Figure 6: Installation Pitch Angle - Shows a car from the side, illustrating the pitch misalignment angle (β) of the mounted module.]

[Description of Figure 7: Installation Roll Angle - Shows a car from the front, illustrating the roll misalignment angle (γ) of the mounted module.]

NOTE: Firmly affix the module to the vehicle body. Select a structurally sound location that is not prone to flexing.

NOTE:

• $PQTMDRPVA is only output when calibration process is completed.
• The standard NMEA message has a fixed output frequency of 1 Hz, however the GGA, RMC, GST and VTG output frequency will shift to 10 Hz after the DR calibration procedure is completed. The combination of $PQTMCFGFIXRATE and $PQTMCFGMSGRATE can be used to configure the output frequency of standard NMEA message. For more details about these commands, see document [1] protocol specification.

3 RTK Input

Quectel LG69T (AM) and LG69T (AP) modules support the RTCM 10403.3 input messages listed in table below.

Table 1: Supported RTCM Input Messages

4 PQTM Messages

This chapter outlines the PQTM messages (proprietary NMEA messages defined by Quectel) for DR function, which are supported by LG69T (AP).

Table 2: Error Code

4.1. PQTMPVT

Outputs the PVT (GNSS-only) result.

Type: Output

Synopsis:
$PQTMPVT,<MsgVer>,<TOW>,<Date>,<Time>,<Quality>,<FixMode>,<NumSatUsed>,<LeapS>,<Lat>,< Lon>,<Alt>,<Sep>,<VelN>,<VelE>,<VelD>,<Spd>,<Heading>,<HDOP>,<PDOP>*<Checksum><CR><LF>

Parameter:

Example:

//No fix:
$PQTMPVT,1,1000,20221225,163355.000,0,0,00,,,,,,,,,,,99.99,99.99*49

//3D fix:
$PQTMPVT,1,31075000,20221225,083737.000,4,3,09,18,31.12738291,117.26372910,34.212,5.267,3.2 12,2.928,0.238,4.346,34.12,2.16,4.38*65

4.2. PQTMDRPVA

Outputs the DR position, velocity and attitude.

Type: Output

Synopsis:
$PQTMDRPVA,<MsgVer>,<Timestamp>,<Time>,<SolType>,<Lat>,<Lon>,<Alt>,<Sep>,<VelN>,<VelE>,< VelD>,<Spd>,<Roll>,<Pitch><Heading>*<Checksum><CR><LF>

Parameter:

Example:

//No fix:
$PQTMDRPVA,1,1000,163355.000,0,,,,,,,,,,,*7C

//GNSS + DR fix:
$PQTMDRPVA,1,75000,083737.000,2,31.12738291,117.26372910,34.212,5.267,3.212,2.928,0.238,4.3 46,0.392663,1.300793,0.030088*5E

4.3. PQTMSENMSG

Outputs sensor information.

Type: Output

Synopsis:
$PQTMSENMSG,<MsgVer>,<TimeStamp>[,<Par1>,...,<ParN>]*<Checksum><CR><LF>

Parameter:

4.3.1. When <MsgVer> = 2

This message is used to output the IMU raw data, these values are read directly from the IMU without any filtering. Refer to IMU reference frame.

Synopsis:
$PQTMSENMSG,2,<TimeStamp>,<IMU_Temp>,<IMU_GYRO_X>,<IMU_GYRO_Y>,<IMU_GYRO_Z>,< IMU_ACC_X>,<IMU_ACC_Y>,<IMU_ACC_Z>*<Checksum><CR><LF>

Parameter:

Example:
$PQTMSENMSG,2,2248864,36.70,0.6118,-0.4064,-0.5419,0.0132,-0.0151,1.0045*34

NOTE:

1. $PQTMCFGMSGRATE can be used to enable or disable $PQTMSENMSG message output. For more details about this command, see document [1] protocol specification.

//Enable $PQTMSENMSG command:
$PQTMCFGMSGRATE,W,PQTMSENMSG,100,2*4C
$PQTMCFGMSGRATE,OK*29

//Disable $PQTMSENMSG command:
$PQTMCFGMSGRATE,W,PQTMSENMSG,0,2*4D
$PQTMCFGMSGRATE,OK*29

4.4. PQTMVEHMSG

Outputs vehicle information.

Type: Output

Synopsis:
$PQTMVEHMSG,<MsgType>,<Timestamp>[,<Par1>,...,<ParN>]*<Checksum><CR><LF>

Parameter:

4.4.1. When <MsgType> = 1

Synopsis:
$PQTMVEHMSG,1,<Timestamp>,<VehSpeed>*<Checksum><CR><LF>

Parameter:

Example:
$PQTMVEHMSG,1,3748292,3.6*1D

NOTE:

1. $PQTMCFGMSGRATE can be used to enable or disable $PQTMVEHMSG message output. For more details about this command, see document [1] protocol specification.

//Enable $PQTMVEHMSG command:
$PQTMCFGMSGRATE,W,PQTMVEHMSG,1,1*4C
$PQTMCFGMSGRATE,OK*29

//Disable $PQTMVEHMSG command:
$PQTMCFGMSGRATE,W,PQTMVEHMSG,0,1*4D
$PQTMCFGMSGRATE,OK*29

4.5. PQTMCFGCAN

Configures CAN interface and baud rate.

Type: Set/Get

Synopsis:
//Set:
$PQTMCFGCAN,W,<PortID>,<Enable>,<FrameFormat>,<Baudrate>,<DataBaudrate>*<Checksum><C R><LF>
//Get:
$PQTMCFGCAN,R,<PortID>*<Checksum><CR><LF>

Parameter:

Result:

• If successful, the module returns:

//Set:
$PQTMCFGCAN,OK*74
//Get:
$PQTMCFGCAN,OK,<PortID>,<Enable>,<FrameFormat>,<Baudrate>,<DataBaudrate>*<Checksum>< CR><LF>

• If failed, the module returns:

$PQTMCFGCAN,ERROR,<ErrCode>*<Checksum><CR><LF>

For details about <ErrCode>, see Table 2: Error Code.

Example:

//Sets the CAN interface
$PQTMCFGCAN,W,0,1,0,500000,0*45
$PQTMCFGCAN,OK*3E

//Gets the configuration of CAN interface
$PQTMCFGCAN,R,0*74
$PQTMCFGCAN,OK,0,1,0,500000,0*16

4.6. PQTMCFGCANFILTER

Configures the CAN filter. The module only receives messages that match the filtering rules.

Type: Set/Get

Synopsis:
//Set:
$PQTMCFGCANFILTER,W,<PortID>,<Index>,<Enable>,<FilterType>,<MsgID_Type>,<MsgID1>,<MsgI D2>*<Checksum><CR><LF>

//Get:
$PQTMCFGCANFILTER,R,<PortID>,<Index>*<Checksum><CR><LF>

Parameter:

Result:

• If successful, the module returns:

//Set:
$PQTMCFGCANFILTER,OK*3E
//Get:
$PQTMCFGCANFILTER,OK,<PortID>,<Index>,<Enable>,<FilterType>,<MsgID_Type>,<MsgID1>,<MsgI D2>*<Checksum><CR><LF>

• If failed, the module returns:

$PQTMCFGCANFILTER,ERROR,<ErrCode>*<Checksum><CR><LF>

For details about <ErrCode>, see Table 2: Error Code.

Example:

//Sets the CAN filter 0.
$PQTMCFGCANFILTER,W,0,0,1,0,0,3E9,1F5*7D
$PQTMCFGCANFILTER,OK*3E

//Gets the configuration of CAN filter 0
$PQTMCFGCANFILTER,R,0,0*68
$PQTMCFGCANFILTER,OK,0,0,1,1,0,3E9,1F5*2F

NOTE:

• If the filter type is mask filter (<FilterType> = 2):
• <MsgID1> is the filter ID, and <MsgID2> is the mask.
• If a mask bit is set to 1, the corresponding ID bit will be compared with the value of the filter ID bit; and if it matches then the message will be accepted, otherwise the message will be rejected.

4.7. PQTMCFGVEHDBC

Configure the vehicle Database for CAN (DBC).

Type: Set/Get

Synopsis:
//Set:
$PQTMCFGVEHDBC,W,<Index>,<MsgID>,<StartBit>,<BitSize>,<ByteOrder>,<ValueType>,<Factor>,<O ffset>,<Min>,<Max>*<Checksum><CR><LF>
//Get:
$PQTMCFGVEHDBC,R,<Index>*<Checksum><CR><LF>

Parameter:

Result:

• If successful, the module returns:

//Set:
$PQTMCFGVEHDBC,OK*6C
//Get:
$PQTMCFGVEHDBC,OK,<Index>,<MsgID>,<StartBit>,<BitSize>,<ByteOrder>,<ValueType>,<Factor>,< Offset>,<Min>,<Max>*<Checksum><CR><LF>

• If failed, the module returns:

$PQTMCFGVEHDBC,ERROR,<ErrCode>*<Checksum><CR><LF>

For details about <ErrCode>, see Table 2: Error Code.

Example:

//Sets the vehicle speed DBC
$PQTMCFGVEHDBC,W,0,3E9,8,16,0,0,0.015625,0,0,300*57
$PQTMCFGVEHDBC,OK*6C

//Gets the configuration of vehicle speed DBC
$PQTMCFGVEHDBC,R,0*26
$PQTMCFGVEHDBC,OK,0,3E9,8,16,0,0,0.015625,0.000000,0.000000,300.000000*2A

4.8. PQTMCFGVEHRVAL

Configures the vehicle reverse gear value based on CAN forward/backward information.

Type: Set/Get

Synopsis:
//Set:
$PQTMCFGVEHRVAL,W,<RVal>*<Checksum><CR><LF>
//Get:
$PQTMCFGVEHRVAL,R*<Checksum><CR><LF>

Parameter:

Result:

• If successful, the module returns:

//Set:
$PQTMCFGVEHRVAL,OK*20
//Get:
$PQTMCFGVEHRVAL,OK,<RVal>*<Checksum><CR><LF>

• If failed, the module returns:

$PQTMCFGVEHRVAL,ERROR,<ErrCode>*<Checksum><CR><LF>

For details about <ErrCode>, see Table 2: Error Code.

Example:

//Set:
$PQTMCFGVEHRVAL,W,2*6D
$PQTMCFGVEHRVAL,OK*20

//Get:
$PQTMCFGVEHRVAL,R*76
$PQTMCFGVEHRVAL,OK,2*3E

4.9. PQTMCFGLA

Configures the lever arm.

Type: Set/Get

Synopsis:
//Set:
$PQTMCFGLA,W,<Type>,<LA_X>,<LA_Y>,<LA_Z>*<Checksum><CR><LF>
//Get:
$PQTMCFGLA,R,<Type>*<Checksum><CR><LF>

Parameter:

Result:

• If successful, the module returns:

//Set:
$PQTMCFGLA,OK*<Checksum><CR><LF>
//Get:
$PQTMCFGLA,OK,<Type>,<LA_X>,<LA_Y>,<LA_Z>*<Checksum><CR><LF>

• If failed, the module returns:

$PQTMCFGLA,ERROR,<ErrCode>*<Checksum><CR><LF>

For details about <ErrCode>, see Table 2: Error Code.

Example:
$PQTMCFGLA,W,1,0.212,0.514,0.113*31
$PQTMCFGLA,OK*7F

NOTE: After issuing this command, the module must be restarted for the command to take effect.

5 Appendix A References

Table 3: Related Documents

Table 4: Terms and Abbreviations

6 Appendix B Special Characters

Table 5: Special Characters