Department of Transportation Releases Civil Monitoring Performance Document

Department of Transportation Releases Civil Monitoring Performance Document
http://sidt.gpsworld.com/gpssidt/content/printContentPopup.jsp?id=596189

May 1, 2009
GPS World

On April 30, the U.S. Department of Transportation released a Civil Monitoring
Performance
Specification document for GPS.

The Global Positioning System Civil Monitoring Performance Specification (CMPS)
is
published and maintained at the direction of the program manager for civil
applications,
GPS Wing. The document outlines current requirements for monitoring of the civil
service
and signals for use by the U.S. government in planning GPS development efforts.
As a
result, many of the requirements contained in this CMPS may be incorporated into
the
next-generation operational control system (OCX), while other requirements may
be
allocated to other government entities for implementation.

The CMPS addresses the current L1 C/A signal and the GPS Standard Positioning
Service
(SPS) provided via that signal. It also includes the planned L1C, L2C, and L5
signals
along with semi-codeless use of the GPS signals.

"The purpose of this document is to provide a comprehensive compilation of
requirements
for monitoring the GPS civil service and signals based on top-level requirements
to
monitor all signals all the time," reads the Executive Summary. "Upon approval
this CMPS
will be used by the GPS community to determine the adequacy of civil monitoring
and
provide focus for any needed monitoring improvements."

The CMPS defines a set of metrics for assessing GPS performance against
standards and
commitments defined in official U.S. Government documents such as the Standard
Positioning
Service Performance Standard, the Navstar GPS Space Segment/Navigation User
Interfaces
(IS-GPS-200), Navstar GPS Space Segment/User Segment L5 Interfaces (IS-GPS-705),
and
Navstar GPS Space Segment/User Segment L1C Interfaces (IS-GPS-800). The CMPS
will be
revised to track changes in these key reference documents.

"The implementation of a system that satisfies these requirements will allow
operations as
well as users to verify that civil GPS performance standards and commitments are
achieved," the document reads. The document also defines the scope and range of
monitoring
needs not directly traceable to the key reference documents but expected by
civil users,
such as the ability to detect defects in signal and data, the rapid report of
anomalous
service behavior to satellite operations for resolution, and notification to
users of the
causes and effects of such anomalies for their various service types (e.g.,
positioning,
timing, and navigation).

The document also addresses the need for archives of key data and events to
support future
improvements in GPS service and to respond to external queries about actual GPS
service
levels.