Precise Positioning Service Performance Standard - GPS.gov

February 2007
GPS PPS PS
2.4 Usage Assumptions for PPS Performance Standards
This PPS PS is conditioned upon certain assumptions regarding use of the PPS SIS. Those
assumptions are as follows.
2.4.1 Authorized User
This PPS PS assumes an authorized user with a keyed GPS receiver. Specifically, the GPS
receiver is assumed to contain current valid PPS keys and have the requisite hardware/software
capabilities to be able to properly use those PPS keys.
This PPS PS assumes the keyed GPS receiver complies with the technical requirements related to
the interface between the Space Segment and PPS receivers as established by IS-GPS-200, ICD-
GPS-224, and ICD-GPS-225 as appropriate.
2.4.2 P(Y)-Code
This PPS PS assumes the GPS receiver is tracking and using the Y-code signals transmitted by
the satellites for best PVT solution purposes. If a satellite is transmitting P-code signals instead of
Y-code signals, then this PPS PS assumes the GPS receiver will track and use the P-code signals
transmitted by that satellite for PVT solution purposes and will use other means to guard against
spoofing. This PPS PS assumes certain keyed GPS receivers may track and use the C/A-code
signals transmitted by the satellites rather than the P(Y)-code signals for operational reasons.
2.4.3 Dual- vs. Single-Frequency Operation
This PPS PS assumes a keyed GPS receiver, which has the hardware capability to track and use
the P(Y)-code signals transmitted by the satellites on L1 and on L2, will track and use both signals
for dual-frequency measurement-based ionospheric delay compensation purposes. This PPS PS
assumes that a GPS receiver which only has the hardware capability to track and use the P(Y)-
code signals transmitted by the satellites on L1 will track and use that signal for PVT solution
purposes and the receiver will use the satellite-transmitted ionospheric parameters for singlefrequency
model-based ionospheric delay compensation purposes. This PPS PS further assumes
that certain dual-frequency GPS receivers may only track and use the P(Y)-code signals
transmitted by the satellites on L1 or on L2, and correspondingly use the satellite-transmitted
ionospheric parameters for single-frequency model-based ionospheric delay compensation, for
operational reasons.
Since Navstar satellites may suffer failures which prevent them from transmitting on both L1 and L2
(i.e., a satellite which transmits L1 only or L2 only), this PPS PS assumes a GPS receiver will track
and use such an L1-only satellite or L2-only satellite as necessary for operational reasons. When a
GPS receiver tracks and uses a particular L1-only satellite or L2-only satellite, this PPS PS
assumes the GPS receiver will use the satellite-transmitted ionospheric parameters for singlefrequency
model-based ionospheric delay compensation of that particular satellite’s signals.
This PPS PS assumes a GPS receiver will take the inaccuracies of dual-frequency measurementbased
ionospheric delay compensation and single-frequency model-based ionospheric delay
compensation into account during operations.
1 st Edition Page 14