CEP  Circular Error Probable
The circle, with a radius given by the CEP value, that represents 50% of all
GPS horizontal errors at a specific Latitude and Longitude. If you were to
measure your 2dimensional position at a given site a number of times, 50% of the
values you measure would be within a circle, centered at the true position, with
a radius given by the CEP value.

DOP  Dilution of Precision
The geometrical effect on GPS accuracy. The position of GPS satellites in orbit determine the DOP values for a given site. The higher the DOP value, the less accurate the position solution.

ERD  Estimated Range Deviation
The difference between the current MCS Kalman Filter state estimate for the satellite's
position and the satellite's position as broadcast in the Navigation Data, along
the path between the receiver and the satellite.

GIANT  GPS Interference And Navigation Tool
GIANT is a simulation tool and missionplanning aid used to determine navigation system performance and its impact on weapons system effectiveness. For instance, the system can be used to improve precisionguided munitions accuracy in a GPSjamming environment.
GIANT models the satellites and user equipment, receivers, and antennae in realworld scenarios, then provides a comprehensive evaluation of the GPS environment. More than 200 registered GIANT users span the acquisition, test, intelligence, and operations communities.

HDOP  Horizontal Dilution of Precision
The DOP value for the 2 dimensional horizontal position. (see DOP)

MCS  Master Control Station
The GPS satellite constellation is controlled from the MCS.

NANU  Notice Advisory to Navigation Users
The notices provided to the navigation community describing GPS satellite outages. NANUs are produced 96 hours in advance of the outage, except in the case of emergencies.

NAVSOL  Navigation Solution
Postprocessed navigation solution errors

ORD  Observed Range Deviation
The observed range difference at a GPS Monitor Station between the measured satellite's position and the satellite's position as broadcast in the Navigation Data.

PDOP  Position Dilution of Precision
The DOP value for the three dimensional position solution. (see DOP)

PPS  Precise Positioning Service
The positioning service provided for authorized military users of the GPS Navigation System.

PR  Pseudorange
A range measurement between a receiver and a GPS satellite, including all errors and bias.

RMS  Root Mean Square
By definition, the square root of the mean of the squares of a collection of numbers.
For a collection of values, the RMS is
for
N values in a collection.

SEM  SEM
SEM format almanacs provided by the 2d Space Operations Squadron

SEP  Spherical Error Probable
The sphere, with a radius given by the SEP value, that represents 50% of all
GPS position errors at a specific Latitude and Longitude. If you were to measure
your 3dimensional position at a given site a number of times, 50% of the values
you measure would be within a sphere, centered at the true position, with
a radius given by the SEP value.

SPS  Standard Positioning Service;
The navigation service available to anyone with a GPS receiver

TTS  Tactical Tool Suite
he tool suite used by the GPS Support Center to produce GPS performance data.

URE  User Range Error
The range error along the path between the satellite and the receiver that the user of the receiver will experience.

VDOP  Vertical Dilution of Precision
The vertical DOP value for the vertical component of a navigation solution. (see DOP)
