The Possibilities

Alternative PNT

The Possibilities

The need to find alternatives to GPS is a top priority for defense, security and critical infrastructure systems.

The demand for continuous PNT operations has become increasingly essential in decision-making, creating a crucial dependence on accurate, reliable and global data. This requires solutions that:

  • Preventing jamming, spoofing and other GPS-denial threats
  • Improving the availability of positioning, navigation and timing in GNSS denied environments
  • Reducing operational and economic vulnerabilities for GPS disruption

GPS has well-documented limitations. The physical realities inherent in providing signals from space are limited under conditions of intense interference or physical obstruction. Yet GPS remains the cornerstone of PNT in military and commercial applications.

See if we are up to your challenge.

Combining sources of position, navigation and timing references is valuable approach to "harden" applications. See if your needs fit with our abilities. 

Collaborating on Alternative PNT Solutions

As PNT experts with a very deep and rich history in precision timing and synchronization, Spectracom is collaborating with governments to provide new thinking for essential applications.

We are helping analyze PNT options, looking closely at affordability, compatibility and interoperability to help push forward the agenda of a robust global PNT service.

Our approach is technology neutral. We believe the best way to solve the challenges of alternative PNT is not to be wedded to specific products. Rather, we work collaboratively to analyze the pros and cons of multiple technologies, searching for the most practical solutions for today that fit in with the needs of the future.

A Focus on Sensor Fusion

Driven by algorithms to capture data from multiple sensors and derive predictive intelligence from that data, sensor fusion serves as the foundation for motion tracking, navigation, context awareness, location based services, augmented reality and more.

We are working to use sensor fusion to reduce navigation ambiguity that is due to feature identification, pattern matching, propagation anomalies, solution geometry, system reliability issues and context ambiguity. We are looking at different methods to handle ambiguous measurements and compare accuracy, reliability, solution availability and processing load.

Market Relevancy

The continuing development of alternative PNT is having significant impacts in the communities we are part of.

The Tool Kit

We are continuously exploring the possibilities for alternative PNT, often in conjunction with technology partners. Here’s our current view on the sources of navigation reference and signals of opportunity.

Reference Navigation



Weak signal but ubiquitous in open sky; mostly accurate



Also, other special transmitters like Locata

Celestial Navigation

Celestial Navigation

And other references points where visible, uses Vision Systems, but inhibited by smoke, fog, clouds



Traditional aircraft navigation today

Signals of Opportunity (SoOps)

Cellular signals


Plus commercial broadcast like TV and radio; ubiquitous but inaccurate



Spotty coverage, inaccurate; Skyhook + E911 requirements

Active transmissions

Active Tx

Radar, Lidar, Sonar

For Autonomous Navigation

inertial measurement unit


Self-containted but not accurate over the long term


Via a network location and proximity data is shared

map matching

Map Matching

Database must be constantly updated to be current



Low cost, place sensors when needed; warehouse locations


Technical Notes and Briefs

More Info
Product Brief describing eLoran as a SecureSync timing reference.
pdf - 784 KB
Friday, July 15, 2016
By: Spectracom

System Diagrams

More Info
A graphical representation of approaches to references for position, navigation and timing
pdf - 597 KB
Saturday, September 26, 2015
By: Spectracom

Success Stories

pdf - 2 MB
Wednesday, March 22, 2017

Solution Briefs

More Info
Despite the fact GNSS systems do a good job providing solutions for diverse applications, they were never designed to be used in many of the ways applied today. Spectracom offers an alternative, resilient timing solution using Satellite Time and Location (STL) technology.
pdf - 2 MB
Monday, January 30, 2017

Presentations and Articles

More Info
Signals from Global Navigation Satellite Systems (GNSS), such as the Global Positioning System (GPS), are very weak and usually cannot be seen indoors or underground. A common method to overcome the problem of receiving GNSS signals indoors or underground is to use a GPS/GNSS repeater with an antenna located outdoors to receive the GNSS signals and an amplifier/antenna to re-transmit the signal indoors. This paper describes the technologies and methods for creating an intelligent repeater system including time synchronization at the nanosecond, microsecond, and millisecond levels, how each synchronization level affects the overall system and methods for achieving each, power level considerations including power level requirements between zones and how they affect transitions from one zone to another, data transfer and example system configurations. While GPS is primarily demonstrated and tested, the possibility for adding other GNSS constellations such as QZSS, BeiDou, Galileo, and GLONASS are also presented.
pdf - 270 KB
Wednesday, November 18, 2015
By: Lisa Perdue - Spectracom