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Maintaining Accountability for Military-Type GPS Receivers

Since 1995, the Forest Service has been able to purchase military-type GPS (global positioning system) receivers. These receivers can receive not only the civilian accessible (CA) signals broadcast from GPS satellites, but also the military P(Y) signals that otherwise are available only to the armed forces. The Forest Service bought nearly 800 of these military-type GPS receivers. They have served the agency well for the past decade in forests and grasslands from Alaska to Puerto Rico.

Until 2000, the accuracy of the civilian signals was purposely degraded by the Department of Defense (DOD). The positioning data was as much as 100 yards in error.

Since 2000, the civilian signal has not been degraded. Now, in open terrain civilian GPS receivers, such as those manufactured by Magellan and Garmin, may be just as accurate as military-type receivers. What’s more, the civilian receivers appeal to field personnel because they are smaller and lighter. Some can even be slipped into a shirt pocket.

The military-type receivers are more rugged than their civilian counterparts. In addition, the military-type receivers often provide an accurate position under a heavy tree canopy when a Garmin or Magellan receiver cannot. But, because civilian GPS receivers are more convenient to use, many Forest Service units often are putting military-type GPS receivers into storage.

[photo] Trimble GPS receiver

Trimble Centurion GPS Receiver

[photo] Rockwell GPS receiver

Rockwell PLGR GPS Receiver

These military-type receivers are a sensitive item and must be stored in a secure area. They must be accounted for and cannot be put on a surplus list. If a Forest Service unit wishes to get rid of a military-type GPS receiver, the unit must turn the receiver in to MTDC. Property personnel need to be aware of this restriction.

The two military-type GPS receivers used by the Forest Service are the Trimble Centurion and the Rockwell PLGR (pronounced “Plugger”).

Both models usually are army green, with the exception of a few PLGRs that are light tan (sand). The Forest Service has many civilian GPS receivers manufactured by Trimble. They are usually bright yellow and black. The Centurion military-type GPS receiver is the only Trimble product that is green.

If your organization has military-type receivers, is not using them, and foresees no future use for them, return the receivers to MTDC.

For more information on military GPS receivers or how to turn them in, contact Bill Kilroy, communications security custodian at MTDC (phone: 406–329–3925; e-mail:

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