TEST-T

Dead Reckoning

Dead Reckoning is a navigation technique used to estimate current position of vehicle , direction of movement, based on its previous position and known speed. It uses additional sensor data to correct the position received from GNSS receiver.

Usage of Dead Reckoning is essential in scenarios where GNSS signal is weak or unavailable, such as underground parking lots, tunnels or dense forests.

Note: Dead Reckoning is enabled for all FT platform devices with gyroscope. At the moment, it’s not possible to disable it.

Key points to understand before utilizing the Dead Reckoning functionality:

• Installation
• Configuration
• Alignment

Prerequisites and Important Settings

• Device mounting quality – Correct device mounting is critical for Dead Reckoning operation. Improper mounting may result in incorrect sensor data and unreliable Dead Reckoning performance.
• Dead Reckoning alignment maintenance – If Dead Reckoning alignment parameters are no longer valid, send the DR_RESET command and perform calibration.
• Electric and hybrid vehicles – For electric and hybrid vehicles, DIN1 should be used for movement detection to ensure correct Dead Reckoning operation.

Basic Operation

Installation

The device must be mounted firmly in the vehicle, with good visibility of the sky. Failure to ensure proper mounting will result in inability to calibrate the device or inaccurate position estimation. DIN1 should be connected to the vehicle ignition ( applicable to trackers with DIN1), it will be used to detect both ignition status and movement, ensuring optimal performance. Following examples ensure that the GNSS antenna is facing towards the sky and there are no physical obstacles, like metal plates, wires, are blocking the GNSS signal.

Good mounting examples ( If vehicle has a heated windshield, you should look for an alternative mounting location in the trunk, on some sturdy metal closer to backseat window):

Dashboard in the middle of the car mount

Beneath the speedometer panel

Above glove box

Bad mounting examples:

Unwanted movements will be detected by the IMU

Metal parts above the mount

Places, where vibration could cause unwanted device movements

Configuration

The Dead Reckoning feature is configurable via the Dead Reckoning section in the GNSS settings group under System view in TCT.

Parameter list can be found here.

Dead Reckoning alignment status

The Dead Reckoning alignment status is a 1-byte AVL ID (1433) that indicates the current status of the Dead Reckoning alignment. The possible values are:

• 0 - Unknown: Dead Reckoning status is unknown.
• 1 - Init: Dead Reckoning alignment is initializing.
• 2 - Coarse: Dead Reckoning is in alignment stage.
• 3 - Stable: Dead Reckoning alignment stage has been completed. Estimation stage is in progress.
• 99 - Standby: Dead Reckoning is in standby mode (NOTE: this status is availabe with 3.7.X or newer firmware version)

Turning alignment

The turning alignment is a 1-byte AVL ID (1434) that indicates the current percentage of the turning alignment of the device.

Straight alignment

The straight alignment is a 1-byte AVL ID (1435) that indicates the current percentage of the straight alignment of the device.

Alignment
Once device mounting adheres to the guidelines, alignment can be performed. The device must finish a specific alignment process to determine its mounting orientation. During this process, there are specific conditions that must be met:

1. The device must be stationary with clear sky visibility for at least 3 minutes.
2. Vehicle speed during alignment should be between 10 km/h and 100 km/h, with varying speeds preferred over extended constant-speed driving.
3. Avoid driving in underground tunnels or areas with poor GNSS signal, otherwise alignment needs to be restarted from the second step.

Standby mode

Standby Mode preserves Dead Reckoning calibration indefinitely, ensuring accurate position estimation after extended GNSS outages (e.g., a week in underground parking), and supports unlimited duration in this mode while maintaining full calibration integrity.

Standby Mode has two behavior options:

• Realignment – Calibration alignment is discarded after the Standby Timeout period.
• Preserve alignment – Calibration alignment is retained during prolonged stationary periods.

Prerequisites and important Settings

• If the device is remounted, send the DR_Reset SMS command and perform a full recalibration. This ensures all orientation- and sensor alignment parameters are refreshed, preventing inaccurate Dead Reckoning calculations after the installation change.

Basic Operation

Entering Standby Mode

The device can enter Standby Mode in two scenarios:

• No movement detected

If the device detects absence of movement, Dead Reckoning enters Standby Mode after the timeout defined by Standby timeout (ID 124) elapses.

• Device enters sleep mode

When the device transitions into sleep mode, the GNSS receiver is switched to power saving mode.

Before GNSS powers down, Dead Reckoning enters Standby Mode immediately, the scenario is paused, and the device proceeds into sleep mode.

Exiting Standby Mode

Standby Mode can be exited in the following cases:

• Movement is detected

When movement is detected, the device exits Standby Mode and resumes normal Dead Reckoning operation. If no movement is detected, Dead Reckoning remains in Standby Mode.

Limitations, Edge Cases & Additional Notes

There are some important things to keep in mind when using the Dead Reckoning functionality. The algorithm tries to correct for these issues, but sometimes they can still affect how well Dead Reckoning works.

• Loss of alignment during drifting – Dead Reckoning alignment may be lost during drifting, when the actual movement vector does not correspond to the vehicle heading. Re‑alignment is required.
• Overshooting - May occur when the vehicle travels straight for more than 50 m at speeds below 20 km/h. In such cases, positional overshoot may be observed. An example is shown in the attached image.

• Position accuracy may decrease - If the device cannot receive a GNSS signal for a long time, the estimated position may become less accurate. This is because the sensors inside the device can only estimate the position for a limited time without help from GNSS.

For example: If a courier spends up to 30 minutes unloading in the underground car park, DR will remain accurate. Otherwise, positioning information will become less accurate.

• Temperature effects - The accuracy of the position can change if the temperature is very different from when the device was last calibrated.
• Alignment reset - If the device loses power or goes into sleep mode, it will need to be calibrated again.

Tip: If alignment auto-save is enabled, realignment will be faster.

• Position jumps after GNSS outages - Multipath occurs when reflected or diffracted GNSS signals reach the receiver, causing position errors. Since Dead Reckoning depends on GNSS for continuous correction, these multipath induced inaccuracies can lead to visible position jumps, especially in urban areas with tall buildings or obstructions.

AVL ID list

Property ID in AVL packet	Property Name	Bytes	Min Value	Max Value	Multiplier	Units	Description
1433	Dead Reckoning alignment status	1	0	99	1		[[{{{model}}}_System#Dead_Reckoning_alignment_status|Dead Reckoning alignment status]]
1434	Turning alignment	1	0	100	1	%	[[{{{model}}}_System#Turning_alignment|Turning alignment]]
1435	Straight alignment	1	0	100	1	%	[[{{{model}}}_System#Straight alignment|Straight alignment]]

Parameter list

Property ID in AVL packet	Property Name	Bytes	Min Value	Max Value	Multiplier	Units	Description
123	Alignment auto-save	-	0	1	-	-	This option saves calibration data to device memory, enabling a faster recalibration after device restart. 0 = Disable 1 = Enable
124	Standby timeout	-	1	65535	1	(s) seconds	The standby timeout is the time after which device will attempt to correct the position based on correction strategy. Default value = 1800
125	Standby mode	-	0	1	-	-	The standby mode is the mode in which the device will attempt to correct the position based on correction strategy. 0 = Realignment 1 = Preserve alignment