Defeating GPS Jammers: Multi-Constellation Tracking for Delivery Vans

Cellular and GPS jammers are now standard kit on the organised hijacking crews working Gauteng. They are imported in volume, sold openly on dark-web channels, and small enough to live on the front passenger seat of an unmarked sedan. A single-frequency, single-constellation GPS receiver, the kind fitted to most SA delivery vans today, is the easiest target the syndicates have. The defence is not exotic. It has existed in commercial GNSS chips for over a decade. It is multi-constellation positioning (GPS, GLONASS, Galileo and BeiDou on the same chip) paired with dead reckoning. This article walks the engineering, in plain terms, for fleet owners running delivery vans through Sandton, Soweto, Kempton Park and the urban canyons in between.

Direct answer

A multi-constellation GNSS receiver tracks four independent satellite networks simultaneously. A jammer can disable one or two, but rarely all four. Dead reckoning then bridges any short period when no constellation is available, by calculating position from accelerometer, gyroscope and wheel-speed data. The combination keeps the vehicle visible to dispatch even when an active jammer is in the cab.

What each satellite constellation actually contributes

There are four major civilian GNSS constellations operating today. Each is run by a different sovereign agency, on different frequency bands, with slightly different coverage characteristics. A modern fleet tracker does not pick one. It listens to all of them at once and uses whichever signals are clean.

Each constellation runs a working satellite roster of dozens of vehicles, with operational counts published by the relevant national agency. The technical point is that a jammer must cover multiple frequency bands across multiple operators to disable all four. Most consumer jammers smuggled into South Africa target the GPS L1 frequency at 1575.42 MHz because it is the original and most widespread civilian signal. A single-frequency L1 jammer kills GPS, but it does little to GLONASS at 1602 MHz, nothing to Galileo's E1 unless the bandwidth is wide enough, and nothing at all to BeiDou's B1. The receiver carries on positioning from the surviving signals.

Why a 4-constellation chip is much harder to jam than a single-GPS chip

Three properties make a multi-constellation receiver a hard target. First, frequency diversity. The four constellations operate across at least four distinct civilian bands. A wide-band jammer that covers all bands simultaneously is large, expensive, and easy to detect with off-the-shelf RF survey tools. Second, signal redundancy. A modern chip needs only four satellites in line-of-sight to compute a 3D fix. With 100-plus satellites visible across the four constellations, a partial attack still leaves enough satellites. Third, signal authentication. Galileo's OSNMA cryptographically signs the navigation data, making Galileo-based fixes resistant to spoofing as well as jamming.

For Gauteng delivery operations, the practical effect is that a jammer switched on as a hijacked van approaches knocks the van's GPS offline but GLONASS, Galileo and BeiDou continue. Dispatch sees the van's track without interruption.

What dead reckoning is, and why it matters in dense city canyons

Dead reckoning calculates a vehicle's current position from its previous known position plus motion since then. It does not need any satellite signal. The inputs are accelerometer (linear acceleration in three axes), gyroscope (rotational velocity), and where available a wheel-speed odometry feed off the CAN bus.

The algorithm integrates these motion inputs over time. The estimate is good for short periods (two to ten minutes of full GNSS denial before drift becomes a problem) and excellent over very short periods (a few seconds of underpass or tunnel coverage with effectively zero error).

Dead reckoning matters in two scenarios. First, urban canyon: a delivery van turning between high-rise buildings in Sandton briefly loses sky view, and dead reckoning fills the gap until the signals reacquire. Second, jamming attack: when all four constellations are momentarily denied, dead reckoning continues the track until the jammer is out of range. In both cases, the vehicle stays on the dispatcher's map.

Teltonika's FMx series and Queclink's GV651CAU are global benchmarks for in-tracker dead reckoning, with tightly-coupled GNSS plus inertial-measurement-unit (IMU) algorithms.

Jamming versus spoofing: two different attacks

The terms are often used interchangeably. They are different attacks with different fingerprints.

Jamming is the deliberate transmission of high-power radio noise on GNSS frequencies to prevent receivers from locking onto satellite signals. The result is that the receiver reports "no fix" or returns a wildly inaccurate fix until the jammer is removed. From the dispatcher's view, the vehicle simply drops off the map. South African fleet directors recognise this as the typical Gauteng jamming attack.

Spoofing is the transmission of fake but plausible satellite signals that fool the receiver into computing a wrong position. The receiver still reports a fix, but the fix is in the wrong place. Spoofing is far harder to execute than jamming because the attacker has to broadcast valid-looking signals that match real-world geometry. Galileo's OSNMA and similar authentication features are specifically designed to defeat spoofing. Most commercial jammers in circulation in Gauteng are crude noise sources, not spoofers.

The implication for fleet directors: a four-constellation tracker handles jamming with frequency redundancy, and Galileo authentication adds a defence against the rarer but more dangerous spoofing attack.

Where Gauteng jamming is most often reported

Several corridors and zones consistently feature in fleet operator jamming reports across Gauteng:

• N1 between Pretoria and Polokwane, particularly at the Hammanskraal stretch
• N3 between Heidelberg and Harrismith, with hot spots around Villiers
• Industrial East Rand, Kempton Park, Boksburg and the Spartan area
• Sandton, particularly around Sandown and Rivonia where high-value cargo collection points concentrate
• Soweto, particularly along the M1 South spurs at off-peak hours

Knowing the geography of the threat lets a fleet director match the technical defence to the route. A long-haul N3 truck and a Soweto delivery van face the same kind of jamming attack but at different time profiles. The hardware specification is similar; the alert routing differs.

A specification checklist for a jamming-resistant delivery van tracker

The list below is the technical specification TG Tracking applies to its Gauteng delivery fleet customers. Anything below this specification is not considered jamming-resistant for the purposes of insurance underwriting.

• Multi-constellation GNSS chipset supporting GPS, GLONASS, Galileo and BeiDou simultaneously
• Multi-frequency reception (at least L1 and L5 or equivalent across constellations)
• 6-axis or 9-axis inertial measurement unit for dead reckoning
• CAN bus interface to draw wheel-speed odometry where available
• Jamming detection flag: the device reports when it detects abnormal RF noise in the GNSS bands
• Buffered storage of at least 50,000 records during connectivity loss
• LTE-M or NB-IoT primary cellular path with 2G fallback for areas where higher-generation networks are degraded
• Dual-SIM or eSIM support for multi-network roaming inside Gauteng

The Queclink GV651CAU and various Teltonika FMx units meet this specification. TG Tracking integrates these devices into TG Online with the jamming flag exposed as a first-class alert, separate from the position-loss alert. This matters because jamming detection often precedes the actual position loss by several seconds, which gives the dispatcher early warning.

How TG Online presents a jamming event to dispatch

A jamming event in TG Online appears as a sequence rather than a single point. The sequence below is the standard view a dispatcher sees on a Sandton delivery van under attack.

`` T+0s Vehicle reports normal multi-constellation fix, all four constellations healthy T+3s Jamming detection flag raised: GPS L1 signal-to-noise drops below threshold T+5s GPS fix lost; GLONASS, Galileo and BeiDou continue T+7s GLONASS fix degraded; Galileo and BeiDou continue T+9s Dead reckoning engaged as confidence flag on the position track T+12s All four constellations regained as the jammer source moves out of range T+15s Jamming detection flag cleared; full multi-constellation fix resumes ``

The dispatcher sees the jamming flag at T+3 seconds, which is well before the position would have visibly drifted. Standard procedure is to call the driver, confirm the vehicle is in normal operation, and escalate to SVR partner if no contact is made.

Next step: audit the GNSS specification on your delivery fleet

Three questions any Gauteng fleet director should answer this week:

• How many constellations does each tracker in our fleet support? GPS only, dual-constellation, or four-constellation?
• Do our trackers report a jamming detection flag, or do they simply drop offline?
• Does our dispatcher see jamming events as a distinct alert class, or buried in the position-loss feed?

If any answer is unknown, the gap is in the equipment. TG Tracking runs a free hardware audit for Gauteng delivery fleets, producing a written report on the GNSS specification of every device and a costed plan for any single-constellation units still in service. Book through the TG Online portal.

Frequently asked questions

How small does a GPS jammer have to be to fit in a hijacker's vehicle?

The most common jammers in circulation are roughly the size of a deck of cards and run off a 12-volt cigarette-lighter feed. They typically have a one to fifteen metre disabling radius depending on output power. Larger units that cover multiple GNSS bands exist but are bulkier and easier to spot during a roadside inspection.

Is using a GPS jammer illegal in South Africa?

Yes. Under the ICASA framework and the Electronic Communications Act, the use, possession and trade of radio jamming devices outside specifically licensed contexts is a criminal offence. ICASA continues to investigate jammer possession and use, and offences are pursued through SAPS in cargo-crime matters.

Will a four-constellation tracker drain the van's battery faster?

Marginally. Modern multi-constellation chipsets draw similar power to single-GPS chips of the same generation, because the additional channels are handled in hardware on the same chip. The real power cost on a delivery van comes from the cellular modem and the reporting cadence, not the GNSS receiver.

Does dead reckoning work after a long period of jamming?

Dead reckoning accuracy degrades over time. Inside the first two minutes of GNSS denial, position estimates are typically within 50 metres of true. By ten minutes, the error often exceeds 200 metres. Dead reckoning is a bridging technology, not a permanent replacement for satellite positioning.

What is the difference between a single-frequency and multi-frequency receiver?

A single-frequency receiver listens on one civilian band (typically GPS L1). A multi-frequency receiver listens on two or more bands across each constellation. Multi-frequency is more resistant to ionospheric error, urban multipath and partial-band jamming, and is the technical baseline for modern fleet trackers from 2024 onwards.

Are there any vehicles where multi-constellation is overkill?

For low-value assets parked overnight in secured premises, a single-GPS tracker may still be cost-justified. For any delivery van running through Gauteng during business hours, the cost difference between single-constellation and four-constellation hardware is small, and the risk-adjusted case for four-constellation is straightforward.

Does TG Tracking sell GNSS chipsets directly?

No. TG Tracking integrates devices from established hardware vendors (Queclink, Teltonika, Digital Matter and others) and provides the local fitment, the South African calibration and the integration into TG Online. The chipset specification is set by the vendor; the operational deployment and the dispatcher view are set by TG Tracking.