How to Design Trackers That Work Without GPS

A GPS receiver draws about 30 milliwatts. A $50 jammer from the internet draws about 500 milliwatts and can overpower that receiver from a kilometer away. This asymmetry explains why GPS jamming incidents in European airspace increased over 20x between 2022 and 2024, and why your next asset tracker design probably can’t rely on GPS alone.

The problem extends well beyond conflict zones. Agricultural sensors in valley terrain routinely lose fix for hours. Maritime trackers crossing the Pacific experience outages when atmospheric conditions degrade signals that already traveled 20,000 kilometers. Wilderness equipment disappears into canyons where satellite geometry makes positioning impossible.

Defense contracts now routinely mandate GPS-independent backup positioning. But this isn’t just a military concern. Commercial logistics faces the same risks, often without recognizing them until deployment.

This guide provides a practical framework for designing trackers that maintain positioning when GPS fails, using technologies you can evaluate and integrate today. No theoretical futures or vaporware, only shipping products with documented performance.

GPS vs. Satellite IoT: A Critical Distinction

Before covering alternatives, a common confusion needs clearing up: GPS uses satellites, but not all satellite-based services are GPS. Understanding this distinction matters for designing resilient systems.

GPS is a one-way positioning system. Your device passively receives timing signals from navigation satellites (US GPS, European Galileo, Russian GLONASS, or Chinese BeiDou). It calculates its own position by comparing arrival times from multiple satellites. The device never transmits anything to the satellites; it just listens.

Satellite IoT is a two-way communication system. Services like Iridium, Globalstar, and Swarm use completely different satellite constellations designed for messaging. Your device transmits data up to these satellites, which relay it to ground stations. Some of these services can estimate your device’s position as a byproduct of the communication link, using Doppler shift analysis or beam identification, but that’s a secondary function, not their core purpose.

The key implication: when GPS fails, satellite IoT still works. They use different frequencies, different satellites, and different physical principles. A GPS jammer doesn’t affect your ability to send a message through Iridium, and the Iridium network can provide a coarse position fix even when every GPS satellite is being spoofed.

This is why satellite IoT appears later in this guide as a GPS backup technology. It’s satellite-based, but it’s not GPS.

Understanding GPS Failure Modes

GPS signals arrive at Earth’s surface with roughly the same power as a car headlight viewed from 10,000 miles away. This weakness creates three distinct failure modes, each requiring different design responses.

Environmental blocking occurs when physical obstacles prevent signal reception. Canyon walls, dense forest canopy, urban canyons, underground facilities, and ship cargo holds all create dead zones. These failures are predictable. You can map them before deployment.

Signal weakness happens when atmospheric conditions, antenna placement, or receiver sensitivity issues degrade an already marginal signal. These failures are intermittent and harder to predict.

Deliberate denial comes in two forms with different implications. Jamming floods the GPS band with noise, causing your receiver to lose fix but report honestly that it has no position. Spoofing transmits fake GPS signals, causing your receiver to report a confident but wrong position. Spoofing is far more dangerous because it can pass integrity checks.

Understanding which failure modes matter for your deployment determines which alternative technologies to prioritize.

Five GPS Alternative Technologies Available Today

Each technology below has shipping products you can evaluate. The right choice depends on your environment, accuracy requirements, power budget, and infrastructure constraints.

LoRa/LPWAN Geolocation

LoRaWAN networks can determine device position without GPS by measuring time difference of arrival (TDOA) across multiple gateways. Your device transmits normally; the network infrastructure calculates position from signal timing.

Commercial options: Semtech’s LoRa Edge platform (LR1110/LR1120 chips) integrates this capability directly. Kerlink and other gateway providers offer geolocation solvers that work with standard LoRaWAN devices.

Best for: Agricultural IoT deployments where you control gateway placement. Fixed infrastructure areas with existing LoRaWAN coverage.

Accuracy: Typically 50-200 meters with good gateway density. Degrades significantly with fewer than three gateways in range.

Limitation: Requires network infrastructure. In remote areas, you’re deploying private gateways, which is feasible for farms but impractical for wilderness roaming.

Cellular Positioning

Cell towers provide positioning through triangulation, timing advance measurements, and (in newer networks) dedicated 5G positioning reference signals. Many cellular modules include this capability.

Commercial options: Quectel modules with embedded positioning, Nordic nRF91 series paired with cloud location services like nRF Cloud. Most cellular IoT platforms offer some form of network-based positioning.

Best for: Deployments with reliable cellular coverage. Agricultural operations spanning rural and semi-urban areas. Supply chain tracking along highway corridors.

Accuracy: Highly variable. Urban areas with dense towers: 50-200 meters. Rural areas with sparse coverage: 1 kilometer or worse. 5G positioning can achieve under 10 meters but requires 5G infrastructure.

Limitation: Coverage gaps make this unreliable as a primary source for true wilderness or open-ocean maritime applications.

Satellite IoT (Non-GPS Positioning)

As discussed above, LEO satellite constellations designed for IoT messaging can provide coarse positioning as a byproduct of their communication function. Doppler shift during satellite passes and beam-level identification give approximate location without relying on GPS navigation satellites.

Commercial options: Globalstar/SPOT devices, Iridium modules with location services, Swarm (now part of SpaceX), and Kinéis. These vary significantly in positioning capability. Some provide beam-level only, others offer Doppler-based fixes.

Best for: Maritime tracking, remote wilderness, polar regions. Anywhere with sky visibility but no terrestrial infrastructure. Critically useful when GPS is being actively jammed or spoofed, since these systems operate on entirely different frequencies and satellites.

Accuracy: Typically 1-10 kilometers. These systems answer “which zone” rather than “which meter.”

Limitation: Latency ranges from minutes to hours depending on constellation and plan. Coarse accuracy limits use cases. Ongoing subscription costs add to total cost of ownership.

Inertial Navigation Systems

INS uses accelerometers and gyroscopes to track motion from a last known position. This is dead reckoning: calculating where you’ve moved since your last fix.

Commercial options: VectorNav tactical-grade IMUs, Xsens MTi series, SBG Systems Ellipse series. For lower-cost applications, MEMS IMUs from Bosch, STMicroelectronics, and TDK InvenSense offer basic capability.

Best for: Bridging short GPS gaps. High-dynamics applications like vehicle tracking. Environments where GPS is blocked but returns periodically (tunnels, parking structures, intermittent canopy).

Accuracy: Entirely dependent on IMU quality and time since last correction. MEMS-grade units typically drift roughly 1% of distance traveled. Tactical-grade units perform significantly better but cost significantly more.

Limitation: Cumulative error makes INS useless for long-duration GPS denial without periodic correction from another source. This is always a backup technology, never a primary source.

Terrestrial Radio and Beacon Systems

For defined operational areas, localized positioning systems using UWB, proprietary RF beacons, or eLoran provide GPS-independent fixes.

Commercial options: Qorvo (formerly Decawave) UWB modules achieve centimeter-level accuracy within beacon range. Locata provides ground-based systems mimicking GPS signal structure. Government-backed eLoran coverage is expanding in some regions as official GPS backup.

Best for: Ports, warehouses, military installations, mining operations. Anywhere you control the environment and can deploy infrastructure.

Accuracy: UWB achieves under 30 centimeters in ideal conditions. eLoran provides roughly 20-meter accuracy across covered regions.

Limitation: Requires infrastructure investment. UWB range limits deployments to defined areas. eLoran coverage remains limited, with strong presence in parts of Europe and Asia but minimal coverage in North America currently.

Matching Technology to Environment

Framework selection requires mapping your operating environment to technology strengths. Here’s how the five approaches apply to three common deployment scenarios.

Remote Agriculture

Agricultural deployments typically feature predictable terrain with potential for infrastructure investment.

Primary approach: LoRa geolocation with farm-deployed gateways. The infrastructure investment pays off across many sensors, and accuracy sufficient for field-level positioning meets most use cases.

Secondary approach: Cellular positioning where tower coverage exists, particularly for equipment tracking on roads between fields.

Design consideration: Power efficiency dominates. Solar-powered sensors need positioning methods that don’t drain batteries during long cloudy periods. LoRa’s passive positioning (calculated network-side) helps here.

Wilderness and Backcountry

Wilderness tracking means no infrastructure and unpredictable terrain.

Primary approach: Satellite IoT provides the only reliable option for truly remote locations. The Garmin inReach architecture (satellite messaging with position reporting) represents the proven model.

Secondary approach: Barometric altimeter plus basic INS provides trail context between satellite fixes. Altitude changes on known trails help disambiguate coarse satellite positions.

Design consideration: User-initiated position requests versus continuous tracking represents a fundamental trade-off. Continuous tracking drains batteries fast; user-initiated reporting limits tracking resolution but extends deployment duration.

Maritime Operations

Maritime environments offer sky visibility but no terrestrial infrastructure, plus additional RF challenges from saltwater.

Primary approach: Satellite IoT for open ocean, potentially combined with AIS integration for vessel identification in shipping lanes.

Secondary approach: eLoran where coverage exists (expanding in European waters). INS bridges short GPS gaps from atmospheric or interference events.

Design consideration: Antenna placement and saltwater-resistant enclosures matter more than in terrestrial applications. Test extensively in actual maritime conditions. RF behavior over water differs from lab testing.

Designing for Sensor Fusion

No single positioning source works everywhere. Resilient tracker design layers multiple methods that compensate for each other’s weaknesses.

Hierarchy design: Define primary, secondary, and tertiary sources with automatic failover. GPS might be primary, with LoRa geolocation secondary, and INS tertiary. The tracker should switch sources without human intervention based on availability and confidence.

Confidence scoring: Weight positioning sources by environmental context. GPS confidence should drop when the tracker detects jamming signatures or enters known dead zones. INS confidence should decay with time since last calibration.

Fusion complexity warning: Kalman filtering and more sophisticated fusion approaches improve accuracy but add integration time significantly. Start simple with hierarchical failover and basic confidence thresholds, then add sophistication based on field testing results. Over-engineering fusion before you understand real-world failure patterns wastes effort.

Several platforms simplify fusion implementation. u-blox modules include sensor fusion firmware. INS vendors like VectorNav provide fusion algorithms designed for GPS/INS integration. For custom implementations, reference architectures from these vendors save significant development time.

Practical Integration Checklist

Before selecting technologies, evaluate each against your project constraints:

Power budget: Active scanning (cellular, LoRa TX) draws significantly more than passive reception. INS accelerometers run continuously at low power but gyroscopes add meaningful draw. Satellite IoT transmission bursts draw high current. Map your power budget to usage patterns.

Form factor: Every RF technology requires antenna space. GPS, cellular, LoRa, and satellite antennas have different optimal placements and may interfere with each other. UWB antennas are small but need line-of-sight.

Cost structure: Distinguish hardware cost, subscription cost, and infrastructure investment. A $5 cellular module with $3/month connectivity costs more over three years than a $30 LoRa module with self-hosted gateways, but only if you’re deploying enough devices to justify gateway investment.

Regulatory requirements: Some RF approaches require spectrum licensing. Satellite IoT services require registration and sometimes export controls. LoRaWAN frequency bands vary by region.

Making This Real in Your Next Design

GPS resilience has shifted from differentiator to baseline requirement. Defense contracts mandate it explicitly. Commercial deployments that skip it discover the gap painfully during real-world operation.

The framework is straightforward: assess your operating environment, select primary and backup technologies matched to that environment, and design a fusion architecture that degrades gracefully.

The implementation is harder. Technology selection requires hands-on evaluation. Datasheets don’t capture real-world performance in your specific conditions. Integration requires expertise spanning RF, firmware, and positioning algorithms.

If you’re building a new tracking device, systems integrators specializing in positioning can accelerate development significantly. If you’re evaluating off-the-shelf hardware, consultants familiar with this landscape can shortcut the evaluation process. Either way, start with your environment and accuracy requirements. The technology choices follow from there.

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