Many DM devices support 'cell tower fallback' for location.

On battery powered devices, this is used to provide a rough location if a GPS (or Wi-Fi) fix fails. This can be useful in extending the localization abilities of a device.

Applies to:

NB: Our ‘Edge’ Range of devices also make use of Cell Tower data and Wi-Fi access point data, along with Digital Matter's Location Engine in order to resolve a position should the device be unable to see any GPS Satellites - particularly indoors. 
See Indoor/Outdoor Tracking. 

In the case of Edge devices, on every connection, Cell tower information is recorded and sent to the server. During any upload, the device performs a scan and immediately transmits this data.

This article refers to our ‘traditional GPS’ devices - where Cell Tower data can be sent should a GPS fix fail. 

*The G150 can be configured to fall back to cell tower location if GPS Jamming is detected. For details see GPS Jamming and Interference Detection

Set up (battery powered devices)

1. Ensure your device firmware supports the feature
2. Set the Cell Tower Fallback parameter to YES (found under the Advanced Tracking parameter tab)

Set up (hard-wired devices)

1. Ensure your device firmware supports this feature
2. Set the Cell Tower Fallback parameter to YES on the GPS Jamming IOs parameter tab. 

Multi-Cell Tower Scanning

Applies to Yabby3.

By default, when cell tower fallback is enabled, it will scan and record one cell tower. The Yabby3 allows for multi-cell tower scanning to be enabled to return additional cell tower information. 

How does it work?

Cell Tower Scan

For battery-powered devices, such as the Barra GPS, each connection involves collecting basic cell ID data (MCC, MNC, and Cell ID). This data is then logged into the Debug logs (FID 0) at the INFO level.

If a GPS fix fails, or GPS is being jammed, ONLY then a cell tower scan is QUEUED. For example, during a trip with 2-minute fixes and 30-minute uploads, if GPS is lost, scans will only be performed at the next upload, not every 2 minutes. Do note that by default, trips will time out if no GPS is available for approximately 5 minutes.

The serving tower is returned. The device will then report to the server:

• Cell ID
• Location Area Code
• Mobile Country Code (MCC)
• Mobile Network Code (MNC)

For integrators - this is Field 28 in the integration documents. Any cell scan results will be sent as an upload with log reason 49 - Cell Tower Connection. Field 36 in the integration documents details the multi-cell scan results. The Cell Tower data field can be sent to third-party servers via HTTP or TCP connectors, or directly to Telematics Guru (TG). In TG, this data is not resolved into a specific location; instead, the Cell ID is listed. However, this data can be sent to an open-source locator for further analysis. Please see how to enable this below. 

Determining the location (Lat/Long)

These values in an of themselves don't constitute the Latitude and Longitude of the device for display on a map. The position must be calculated and this can be done through various location services like Google's Geolocation API. The data can be passed to this service via API call and the Lat/Long is returned. Services of this nature charge a fee per lookup or per month. 

Accuracy

The cell scan is typically accurate to within 1km. On NB-IoT, it can be much worse as the cells are wider. 

So it is useful for a rough idea of where your device is i.e., 'has it left the depot?', what suburb am I in?, not ‘what street am I on?’

Applications

As mentioned, the accuracy of a Cell Scan is not great in comparison to a GPS fix. It can be useful as a 'last resort' fix. If you are expecting to be regularly indoors, the Edge device range may be a better choice. Additionally the cost of look-ups must be factored in to the equation - however this feature is useful for:

Tracking assets in shipping containers

Often GPS fixes will fail when a device is placed inside a shipping container, but the device can still connect to the cellular network. When out in the field, the asset can be tracked via GPS. A typical problem is that once the device is loaded into the container and GPS fixes fail, we may be able to get uploads but we lose all visibility of device location. It will report the exact same GPS location (i.e. the last valid fix) until the container is unloaded (maybe not until it reaches another country!) Cell tower fallback is enough to give us a rough location, so we know it left the port/depot/warehouse - which is invaluable when managing the movement of shipments as an operational tool.

Theft/tampering prevention

The ability to fall back to a cell location while GPS is jammed means we can still track a devices rough location in the event of jamming. Thieves may attempt to jam GPS signals, if successful, the device will stop updating it's location as it cannot acquire new GPS fixes. Cell Fallback will give a rough location and may enable the asset to be recovered. 

Cell Tower Fallback on Telematics Guru

The devices will send Telematics Guru the raw Cell Tower data which is stored in the Telemetry. Google's Geolocation API may be used to calculate the device's position should you require an estimate, i.e. when recovering an asset. 

To view the Cell Tower Data button - the organization must have Cell Tower Data functionality enabled.