Just seen an interesting transmission appear on your spectrum, but now it’s disappeared? Need to know where it came from, but you weren’t running a geolocation task at the time? Tough luck, it’s gone forever. If you’re lucky, you can sit there staring at your screen and it might pop up again.

Sounds ridiculous? That’s what we thought, which is why we’ve developed our geolocation in post-processing capability, so you can perform TDOA geolocation retrospectively on recorded spectrum data.

Geolocation in post-processing adds flexibility to your spectrum monitoring missions, enabling applications previously unachievable.

Remote autonomous monitoring

For example, you might want to leave Nodes in a remote area to operate autonomously. If there’s no network infrastructure available to send spectrum data over IP, then real-time geolocation will not be possible. However, the Node can be left to record spectrum data which is then retrieved later for geolocation in post-processing. In many scenarios not requiring a real-time geolocation and response to detected signals, this is the perfect solution to get around infrastructure constraint issues.

Combine with triggered record

If Nodes are being left for long periods of time and you don’t want to end up wading through hours or days of uneventful recorded data, you can also use our triggered record capability. This allows frequency masks to be set up so that only signals of interest are recorded. You might then be left with just a few minutes of interesting signals which you can analyse and geolocate – a much lighter and less tedious workload than if you had to search the data for them first.

Never miss a signal

Real-time, but short duration signals are another application. Many signals which transmit as short duration bursts, such as GSM or WiFi, will retransmit at regular intervals so you probably won’t miss your chance to geolocate them. With some signals, however, you will only get one chance. For example, a vehicle using a GPS jammer might have driven through a network of Nodes or an employee in your secure facility may have briefly switched on a contraband device which sends out only a short sub-second transmission. Recording the I/Q data will ensure you can locate such devices even if you were not geolocating in that frequency band at the original time of the transmission.

Process and geolocate signals in bulk

Post-processing is also ideal for less time-critical applications which don’t require real-time geolocations. In these scenarios, it may be more efficient to collect data over days, weeks or months and go back to analyse it in bulk at a later date, deciding what’s important and requires geolocating after the fact.

Example: Military – post-incident intelligence

A military unit is driving along a road when they come under attack from an insurgent group. Explosive devices have been detonated on the roadside and they are now taking fire. At this time, the priority is to respond to and neutralise the immediate threat. However, once the incident is over some post-event diagnosis using spectrum data can be carried out. For example, to determine if the explosives were detonated remotely and whether the signal came from the site of the incident, suggesting it was one of the insurgents involved in the subsequent gun attack, or further away indicating there are members of the group still at large.

Example: Industrial Interference

Some operations might mean that the need to geolocate (or look at spectrum at all) is known only in hindsight. For example, a factory is using continuous monitoring for avoiding and diagnosing spectrum interference and congestion issues. They decide to record data so they don’t have to respond to issues in real time. A problem with the factory’s wireless automation system prompts them to go back and look at recorded spectrum data to diagnose the issue. If interference is identified, they can geolocate to find the source. Even if the source is no longer in the same place, e.g. it might have come from a delivery vehicle, cross-referencing geolocation data with CCTV and event logs can still be used to diagnose the cause of interference.

Geolocation in post-processing, along with automation features for triggered record or alarms, enable RFeye® users to achieve more flexibility with their spectrum monitoring, to analyse and geolocate when and how it suits them.

Find out more about our geolocation capabilities in our White Paper.