Five Centimeter Global, Real-Time Accuracy - Without a Base Station

The first of its kind, this global satellite-based augmentation system (GSBAS) provides five centimeter positioning accuracy on a worldwide basis, completely independent of geographical boundaries, allowing users to roam freely while maintaining the most precise positioning information.

About StarFire™


The StarFire™ global subscription service provides real-time accuracy typically better than 5cm (<2 inches). Its globally corrected signal is available virtually anywhere on the Earth's surface on land or sea, from 72ºN to 72ºS latitude.


To accomplish this, StarFire™ utilizes a network of more than 40 GNSS reference stations around the world to compute GNSS satellite orbit and clock corrections. Two completely redundant processing centers and multiple communication links ensure the continuous availability of StarFire™ GNSS corrections. These corrections are broadcast via geostationary satellites, providing worldwide coverage and enabling precise real-time navigation without the need for local ground base stations.


As an alternative to delivery of corrections via satellites - NavCom offers a StarFire Over IP software option that allows users to access StarFire corrections over the Internet, giving them access to the same reliable five centimeter global positioning accuracy without the need for a base station. Users are able to access StarFire corrections in those situations when satellite delivery might be unavailable, such as deep urban canyons or very high latitude locations.


The StarFire Network is a major advance from earlier ground based augmentation systems because it considers each of the GNSS satellite signal error sources independently. GNSS satellite orbit and clock corrections are calculated from a global tracking network of dual frequency receivers. These corrections are transmitted via geo-stationary satellite links direct to StarFire receivers, resulting in minimal data latency and worldwide operation with a minimum 10° look angle to the geostationary satellites. All StarFire receivers use a multi frequency GNSS receiver that measures the ionospheric delay for each satellite. Tropospheric zenith delays are calculated from a multi-state time and position model aided by redundant satellite observables.


Redundant data links, geographically separated processing hubs, and dual satellite uplink equipment ensure continuous reliable positioning. The system is inherently robust, with the ability to calculate a full set of corrections even if multiple reference stations were to become unavailable. With an uptime of 99.999%, customers can be confident of the global availability and accuracy of the system.


During the mid-1990’s, Deere &Company challenged NavCom with developing a proprietary, global, cost-efficient GPS correction network capable of providing greater accuracy than existing available systems.


In response, NavCom implemented a fully redundant, worldwide, dual-frequency GPS reference network that was free from regional boundaries. It also devised new processing algorithms to allow for optimal compression of GPS correction data, to reduce both satellite bandwidth needs and operating costs. Launched globally in 1999, the StarFire™ Network uses the GPS satellite system, L-band communication satellites, and a global network of reference stations to deliver real-time high precision positioning.


In, 2011, NavCom launched StarFire™ GNSS, which supports GPS + GLONASS corrections and also provides improved real-time accuracy of five centimeters. StarFire GNSS utilizes Deere proprietary algorithms combined with high precision measurements from Deere's upgraded global tracking network of multi-frequency, multi-constellation SF-3050 integrated StarFire™/RTK GNSS receivers to provide enhanced accuracy and performance anywhere, anytime.

StarFire™ vs. dGNSS


As a Global Satellite-Based Augmentation System (GSBAS), the StarFire™ Network holds a significant advantage over differential GNSS (dGNSS) systems. Since no base station is required, the StarFire™ user is free to roam, with no limitations on range. StarFire™ provides one set of corrections for the entire world, as opposed to dGNSS systems' baseline-dependent regional corrections, which are geographically limited.

GSBAS vs. dGNSS Systems

Learn more about GSBAS vs. dGNSS systems.

In order to evaluate the satellite positioning options available, the primary error sources contributing to the corrections need to be understood.

Reference and rover errors include:

  • Satellite Clock
  • Satellite Orbit
  • Ionosphere
  • Troposphere
  • Multipath
  • Earth Tides
  • Receiver Clock
  • Receiver Biases

How these are handled can be placed into two broad classes: differential GNSS (dGNSS) systems and Global Satellite-Based Augmentation System (GSBAS) systems.

dGNSS Systems

dGNSS provides relative positioning; these positioning options determine corrections at the Earth's surface, either at individual sites or averaged over a region. These corrections are an amalgam of primary reference error sources and are transmitted to the user via radio or satellite link. User coordinates are determined relative to the reference site(s). Accuracy degrades with distance from the individual reference site or the regional boundary, primarily because of differential ionospheric and tropospheric effects, satellite orbits, and clocks. Examples of correction services include:

  • Beacon dGNSS
  • Commercial dGNSS
  • RTK / Network RTK
  • Widelane RTK

Widelane RTK is a relative newcomer, which is only available in the few areas of the world that require high accuracy on a regular basis for oil and gas exploration surveys.


Importantly, GSBAS systems provide absolute positioning, meaning they do not determine position relative to some fixed point of the Earth's surface. Instead, they determine a position within a space-based reference frame, thus they may also be considered to be within the Space Domain group. 

Satellite communication links are used for some dGNSS systems, so the term GSBAS does not relate to the communication link used but instead describes the nature of the corrections, i.e. that they are for the satellites. This class includes:

  • Standalone GPS
  • WAAS
  • MSAS
  • StarFire™

Augmentation for Standalone GPS consists of satellite orbit and clock updates which are generated by the GPS Ground Control Segment and distributed to the user with an ionospheric model in the GPS signal structure. It is this basic principle of determining each error source instead of amalgamating them which distinguishes GSBAS from dGNSS.

Reference Data


In addition to our standard StarFire™ subscription service, NavCom provides select StarFire™ Reference Data to customers in more specialized application areas such as the wireless, LBS and military industries. This Reference Data, both real-time and archival, is ideally suited for the following applications:


  • Timing information in the Wireless Service Industry
  • Satellite acquisition and information in the Location-Based Service (LBS) industry
  • Mission planning and navigation simulation in the military and government operations
  • Satellite monitoring in GPS operations
  • Post processing in the survey industry

Real-time GPS Satellite Data (SV Ephemeris Data)

  • Fast position acquisition - enables low cost L1 GPS chipsets to acquire position in 6 seconds, as opposed to the typical 1 minute (i.e. it reduces acquisition time by one order of magnitude.)
  • Allows for satellite monitoring in GPS operations
  • Aids in mission planning and navigation simulation
  • Typical customer: Military, Wireless Providers - LBS/E-911 services

Real-time StarFire™ Corrections

  • Provides L1 chipsets with significantly greater position accuracy
  • Improves accuracy from ~30m to 1.5m
  • Typical Customer: Wireless Providers - LBS services

Real-time Satellite Data & Corrections

  • Position is acquired in 6 seconds as opposed to 1 minute
  • Accuracy is improved to 1.5m as opposed to ~30m.
  • Typical customer: LBS service providers (i.e. child monitoring services)

Real-time Timing Reference Data

  • Low cost, high-resolution alternative to current timing elements
  • Providers of cellular infrastructure have a cell-station requirement of providing timing resolution within 7 microseconds
  • Our Timing Reference Data exceeds the 7 microsecond requirement with a provided resolution of 12.5 nanoseconds, at a fraction of the cost of typical solutions
  • Typical customer: Wireless Providers – Infrastructure

Archived Satellite Data & Corrections

  • Post processing of measurement data to achieve millimeter-level accuracy
  • Potential Customer: Survey Industry

Subscription Service


StarFire™ five centimeter positioning is available on a subscription basis to end users of our SF Series GNSS receivers. There are two types of StarFire™ subscription licenses:


  • Land Only (excludes all oceans/offshore)
  • All Areas (global coverage)


Licenses can be purchased for the following time increments:


  • Monthly (30 days)
  • Quarterly (90 days)
  • Semi-annually (180 days)
  • Annually (365 days)


Typical applications that benefit from StarFire™ performance, accuracy, and availability include:


  • Land Survey
  • Offshore Positioning
  • Precision Agriculture
  • Aerial Photogrammetry and LIDAR
  • GIS and Asset Mapping
  • Machine Control


NavCom now offers StarFire via Over the Air Licensing: NavCom’s Over The Air (OTA) StarFire Licensing is the easiest way to install a StarFire license. The installation of a purchased license is accomplished via radio broadcast. OTA StarFire Licensing is especially convenient for receivers in remote locations in the field.

*The number of StarFire™ broadcasting satellites and their locations are subject to change without notice.