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The GPSOC uses GPS ephemeris and clock errors to provide accurate real-time situational awareness that is plotted as colored contours on a global map.

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The New GPS Operations Center for Warfighters

A recently upgraded GPS Operations Center has added new software tools that enable it to provide military GPS users with improved models of their equipment's functionality in operational environments. among other benefits, this lets users anticipate thier PPS and SPS positioning accuracies in real time.

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Inside the Master Control Station at the 2nd Space Operations Squadron (2SOPS), Schriever Air Force Base, Colorado, crews continuously monitor and control the GPS constellation’s navigation signals. By doing so, 2SOPS keeps the GPS signal as accurate as possible, making it a phenomenally successful global utility.

Yet, as GPS users know, other factors — such as differences in receivers, terrain, environment, and platforms — can affect navigational accuracy in the field.

So where do warfighters turn when they need help determining their navigation accuracy? That’s where we in the GPS Operations Center (GPSOC) come in.

Operated by 2SOPS, the GPSOC is one of three centers of excellence that military, civil, and commercial GPS users can turn to for navigational accuracy assistance (see related story “The Big Three”).

The GPSOC primarily serves the needs of the Department of Defense (DoD): Military users of GPS can call us to learn what’s affecting their receivers, and mission planners rely on our unit to provide specific in-field information.

The GPSOC also makes routine dilution of precision (DOP) and accuracy predictions as well as past accuracy assessments for theaters requiring the information. GPSOC also provides analysis for military exercises. Through these functions, we bridge the information gap between the GPS user and GPS control segments.

Recently, the center upgraded its operational baseline of software tools to help support all GPS customers, shifting the focus from contractor-specific tools to more standardized software. Drawing on commercial off-the-shelf (COTS) and government off-the-shelf (GOTS) capabilities, we can now tell GPS users around the world whether situational circumstances are causing disruptions in their service. This article describes how these new software resources helps GPSOC do its job better.

Upgrading Capabilities
In January, the GPSOC installed its first COTS product, a navigation software tool. This software suite allows us to model specific GPS receivers, terrain, environmental characteristics, and land, sea, air, space, and weapon platform details, while providing receiver interference analysis to dynamically model GPS receiver performance.

The GPSOC uses the navigation software tool as its primary operations resource, but we employ additional software to complete our cadre of analysis capabilities. GOTS tools supply interference modeling and analysis and bring additional insight into constellation behavior.

As an example of how the GPSOC operates, if military mission planners using a precision guided munition need to know how well GPS will perform at a specific site over a given time, they provide us location coordinate information. We model GPS and other effects in which they may be interested. If terrain is a concern, we can also model that, but we make sure that the correct receiver model is used, because various receivers act differently in different situations.

Another layer that can be added using the navigation software tool is the effect of jamming on the receiver. To broaden the scope of understanding, the planners can also request a regional analysis. In this case, we run the same scenario over a larger grid and display the analysis on top of imagery or maps of the area, which helps the planners discern navigation accuracy over a wider location and allows them to pinpoint locations in areas of interest with specific accuracy. Static accuracy maps such as this can show the maximum error over time, or we can produce an animated map that outputs accuracy as a function of time over the region.

This level of analysis is much broader than we’ve ever done before. Previously, daily predictions and accuracy assessments showed the signal-in-space (SIS) accuracy of the GPS constellation and the noise behavior of a typical GPS receiver.

This provided general accuracy characteristics for mission planning, but mission planners want and need more. They need to know how their GPS receivers will perform at a certain place and time, under specific conditions, so they can plan exacting, precise maneuvers.

Some of the new capabilities the GPSOC can provide using its new navigation software tool include:
• real-time situational awareness of PPS and SPS accuracy
• user-specific receiver and platform modeling for accuracy and DOP predictions
• environmental effects modeling
• interference and jamming modeling, with user-defined characteristics
• satellite outage streamlining for analysis
• parallel processing capability.

In addition to traditional SIS, the GPSOC is also exploring ways to provide GPS data via net-centric means.

(For the complete story, including figures, graphs, and additional resources, download the PDF above.)


The GPSOC uses Navigation Tool Kit, developed by Analytical Graphics, Inc. (AGI), of Exton, Pennsylvania, as its primary operations tool. The GPSOC also subscribes to AGI’s Real-Time Navigation Data Service.
The government off-the-shelf (GOTS) equipment acquired by GPSOC includes General Dynamics’ GPS Interference And Navigation Tool (GIANT) and NASA Jet Propulsion Lab’s Integrity Monitor and Generic Area Limitation Environment – Lite (GALE-LITE).

Author Profiles

Major Chuck Daniels is the director of the GPS Operations Center, 50th Space Wing, Air Force Space Command, Schriever Air Force Base, Colorado.

He is responsible for ensuring all U.S. Department of Defense personnel worldwide using GPS receive accurate and current position, navigation, and timing analysis and support.

Daniels leads a contractor and military team of over 20 personnel to complete daily tasks.

His career includes assignments in a variety of space operations positions. Following undergraduate pilot training, he trained as a space operator at Lowry AFB, Colorado, and has served in space surveillance, missile warning, and satellite command and control.

He was initial cadre with Milstar in Sunnyvale, California and served as the operations officer for development and standup of the strategic missile warning backup to Cheyenne Mountain at Offutt Air Force Base, Nebraska.

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