At times, a device may fail to obtain a new position. Possible reasons, in order of likelihood, are listed below. 

1. The device is temporarily in an area of limited/no GPS signal, like a parking garage or heavily built up area. 
2. The device is installed such that the signal is blocked:
   1. Buried deep in an asset, around lots of metal
   2. GPS antenna is poorly oriented, facing down towards the ground
3. The parameters have been configured such that they are overly restrictive
   1. The device may be set up with short GPS timeouts so the device gives up before it can get a ‘lock’ 
   2. The parameters are configured to require a degree of accuracy that can't be achieved before the timeout elapses. 
4. There is a device (hardware) issue. 

In general

• (1) will resolve itself once the asset moves. 
• (2) is resolved by adjusting the placement of the device. 
• (1) and (2) may be working in tandem - i.e. the device is placed in a less than optimal position on the asset. So it can get a fix OK when in an open area, but once the signal becomes worse, it then begins to fail GPS fixes. 
• (3) can be resolved by reverting any GPS Fix parameters to defaults. 
• After some remote troubleshooting (covered below) - (4) may require the device to be returned under Digital Matter’s Returns Policy (“RMA”) 
   

Troubleshooting your device: 

1. Check Device Placement 

• Avoid Obstructions: Ensure that the device is not enclosed in a metal container or placed near large buildings, metal structures, or reflective surfaces. 
• Open Sky Access: Position the device in an area with a clear view of the sky to facilitate satellite signal reception.

If the device is currently in a location with limited satellite visibility, relocating it to an open area may resolve the issue. If that still does not rectify this situation, we can rule out placement. 

2. Wait for Better Coverage:

• Signal Acquisition: Sometimes, the GPS device may need a few minutes to acquire a strong signal, especially if it has been turned off for a while or moved to a new location. Be patient and allow the device time to establish a connection with the satellites.
   
• If the asset has been moving to a variety of locations over time, yet still not updating, we can rule GPS signal/coverage out as the cause. 

3. Adjust System Parameters 

Adjust Settings: Consider relaxing GPS accuracy requirement timeout settings. This can help improve the performance of the GPS device.

These parameters apply to battery-powered, non-Edge devices 

GPS Timeout

This is the maximum time to wait to get a fix. 
Extend the maximum wait time for a GPS fix in poor signal conditions if fixes repeatedly fail.

This may result in reduced battery life - as the device may spend longer ‘searching’ for satellites. 

Satellite Timeout

At least 4 satellites are required for a 3D GPS fix. The device has advanced power-saving functionality to give up early if we do not see 1 satellite within 20 seconds, 2 within 25, 3 within 30. 

The assumption being if we cannot even see one satellite early - we're probably in a basement, so it's unlikely we will ever see 4, no matter how long we search - so we may as well quit the fix. 
Try setting your parameters as follows to prevent the device from giving up early. 

Relax GPS accuracy requirement timeout settings.

Require 3D Fix
Setting to NO will mean we can get a fix with 3 satellites instead of 4 - but altitude isn't returned. Setting to No may help in acquiring a fix in low signal conditions.

Notes on Dilution of Precision (DOP) And Specifically PDOP

If these have been adjusted, best to revert to the default (remove the parameter tab) and see if the issue persists.

• PDOP
  • If it is much lower than the default of 5.0 (i.e 1.0, 2.0) - best to revert to defaults
• Position Accuracy
  • If it is much lower than the default 50, fixes may be being discarded. Revert to 50 or even try setting to 100 temporarily
• Speed Accuracy
  • Revert to default
• Discard First N Fixes
  • Set to 0 temporarily
• To revert all these parameters to default, simply remove the parameter tab and update parameters

Further Troubleshooting

If we have ruled out placement, GPS coverage, and parameters as an issue, we can configure the device to record additional verbose logs about GPS fix acquisition. 

1. How many satellites it is able to see
2. Their strength
3. How long it takes to acquire a fix if succesful. 

Steps to enable debug logging

1. Login to Device Manager
2. Select the device(s) - explained here
3. Set the debug level - explained here
4. To enable debugging, be sure to set the GPS module to Info - others can be set to Severe. 
   1. Check the Debug Expiry (when the extra logging will end) is set far enough in the future so that you can receive enough logs.
5. Wait for the device to connect and receive the logging change instruction. From this point on additional logs will be captured. 
6. After this change instruction, on the next fix attempt/upload extra debug information will be uploaded to the server. 

(5) and (6) mean that after you enable debug logging - you will see the debug logs after the 2nd connection to Device Manager. 

Alternatively, the logs can be enabled, retrieved via a DM-Link cable 

1. If you have a DM-Link cable, follow the steps in the guide to pull the debug logs from your device, and send the CSV file to your local support team. 
   1. DM Link Guide
   2. Contact Support
2. Send through the following information to your support team,
   1. Device serial
   2. Device type
   3. Description of the issue

Interpreting the Logs

When the debug level is set to Info, all GPS debug messages will appear in the log. In addition to individual fix times, signal level diagnostics whenever a fix takes longer than 36 seconds, or the GPS decides to stay awake after a fix to collect more satellite information. Please note that while debug messages are enabled, uploads will use extra data.

Depending on your device, the data may look slightly different, as the way different GPS components report the data can vary. 

Debug[GPS][Warn]: GPS manager - Fix timeout:
This indicates the GPS module has failed to get a fix in the allocated time. The device may sleep or try again.

Debug[GPS][Info]: TTFF=133s PDOP(x10)=33 3Dfix=1
This states that the device obtained a fix in 133 seconds with a PDOP of 3.3

Debug[GPS][Info]: Valid=135s PDOP(x10)=19 3Dfix=1:
The device obtained a valid fix in 135 seconds with a PDPO of 1.9. This is after the fix has met the minimum requirements for a good fix. These are usually configurable in System Parameters.

Debug[GPS][Info]: SAT4 42322,38000,35322,29322:

Signal strengths reported by the module.

The number immediately after the "SAT" is the number of satellites the receiver is tracking - in this example 4.

The first 2 digits of the numbers represent the "Carrier To Noise" ratio (C/No) in dBHz and is an indicator of the received GNSS signal strength. The higher the C/No value is, the better is the strength, and therefore the quality of the received signal.

In our testing, we consider values above 40 as excellent, but chances are that you will only get above 40 when conditions are near perfect - so don't stress over these numbers. 
The main reason we have surfaced these values via the debug messages is that values at extremes indicate something is wrong with the GNSS / antenna subsystem, and any values between those extremes are OK.
These messages are logged every 60 seconds when in debug mode. This example message suggests it is tracking 4 satellites. In this example the highest signal strength is 42, which is considered strong.
The other numbers are displayed for internal debugging purposes.

Debug[GPS][Info]:
Q04*41,G01*41,R23*12,R11*27,B36*33,E25*39,G02*38,R07#32,R08*23,R10*31,R09*38,B04*37,B45*39,Q02*29,E16*41,B19*38,E03*38,Q07*33,E15*26,B38*35,

G - GPS (Global Positioning System): The American satellite navigation system.
R - GLONASS (Global Navigation Satellite System): The Russian satellite navigation system.
Q - QZSS (Quasi-Zenith Satellite System): The Japanese regional satellite system.
B - BeiDou: The Chinese satellite navigation system.
E - Galileo: The European Union's satellite navigation system.

Counting the alphabets represents the number of satellites the device saw, and the number after the ' * ' for each satellite represents signal strength.

In this example, the logs show that the device has acquired a fix. 

Potential Issues, Examples:

 Debug[GPS][Info]: SAT0
 Debug[GPS][Info]: SAT1

If no numbers are reported after SATX, for repeated logs - this means that the value was too low to report and has been omitted.

The device needs at least 4 satellites to acquire a valid fix.
So this means a log like: Debug[GPS][Info]: SAT8 42322,38000,35322,29322,28723,26100,19500,16000 shows the device has sufficient signal to acquire a fix. But SAT2 16000 11520, it does not

In this example, the device may be completely shielded by GPS, or the LNA (low noise amplifier) on the device is potentially faulty. In this case, the GPS module is working, so no errors are detected, but the weak signals are not being amplified such that the device can use them.

Solution:

If a device is away from any equipment and has a clear view of the sky, yet still reports these logs, it is likely that there is an LNA fault and the device needs to be replaced. So, to resolve -  trigger a GPS fix attempt with the device in the open. If there is no change in the GPS Debug logs, follow Digital Matter’s Returns Policy (“RMA”) 

Error-  Turning Off

Debug[GPS][Crit]: Error - Turning off
Debug[GPS][Crit]: Error Count = 3 on cfg port -> Error Off

This log may mean one of two things

1. The device attempted and then failed to get a GPS fix, so it followed normal procedure and turned off the GPS module 
2. There is a fault with the GPS. This might be the case if this log is seen repeatedly on every fix attempt over an extended period. 

If repeated logs of this type are shown, the device likely has a fault with the GPS module and will need to be replaced. 

These logs will appear even without following the above steps to turn on extra logging, as they are of log level Critical, meaning they are always logged by default.

Bad length 

Debug[GPS][Info]: Bad length NMEA/PMTK: $GNGGA,145$PMTK011,MTKGPS*08 ,N*2C 323,,,N*58 .63,1.09*07 1.0,M,,*69 GPS*08

This message appears when the device is switching between the binary and NMEA formats, as there is often no assurance of sentence completion during the switch-over process. 

This log does not prevent a GPS fix, however, we advise updating the device to the latest firmware version.