To civil differential systems with the removal of sa

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: nal Doppler. Doppler errors are driven by predicted state errors in the transmitted satellite velocity vector, and the slow drift of the on-board satellite frequency standard. The best indicator of steady state range rate error due to predicted satellite ephemeris and clock states is the rate-of-change of SIS UREs. Typically, the range rate error associated with steady state SIS UREs is less than one millimeter/second RMS. Page A-38 October 2001 GPS SPS Performance Standard APPENDIX B Key Terms, Definitions, and Acronyms SECTION B-1 Key Terms and Definitions Almanac Longitude of the Ascending Node (Ωo): Equatorial angle from the Prime Meridian (Greenwich) at the weekly epoch to the ascending node at the ephemeris reference epoch. Coarse/Acquisition (C/A) Code: A PRN code sequence used to modulate the GPS L1 carrier. Corrected Longitude of the Ascending Node (Ωk) and Geographic Longitude of the Ascending Node (GLAN): Equatorial angle from the Prime Meridian (Greenwich) to the ascending node, both at arbitrary time tk. Dilution of Precision (DOP): The magnifying effect on GPS position error induced by mapping GPS ranging errors into position within the specified coordinate system through the geometry of the position solution. The DOP varies as a function of satellite positions relative to user position. The DOP may be represented in any user local coordinate desired. Examples are HDOP for local horizontal, VDOP for local vertical, PDOP for all three coordinates, and TDOP for time. Equatorial Angle: An angle along the equator in the direction of Earth rotation. Geometric Range: The difference between the estimated locations of a GPS satellite and an SPS receiver. Groundtrack Equatorial Crossing (GEC, λ, 2 SOPS GLAN): Equatorial angle from the Prime Meridian (Greenwich) to the location a groundtrack intersects the equator when crossing from the Southern to the Northern hemisphere. GEC is equal to Ωk when the argument of latitude (Φ) is zero. Instantaneous User Range Error (URE): The difference between the pseudo range measured at a given location and the expected pseudo range, as derived from the navigation message and the true user position, neglecting the bias in receiver clock relative to GPS time. A signal-in-space (SIS) URE includes residual orbit, satellite clock, and group delay errors. A system URE (sometimes known as a User Equivalent Range Error, or UERE) contains all line-of-sight error sources, to include SIS, single-frequency ionosphere model error, troposphere model error, multipath and receiver noise. Longitude of Ascending Node (LAN): A general term for the location of the ascending node – the point that an orbit intersects the equator when crossing from the Southern to the Northern hemisphere. Longitude of the Groundtrack Equatorial Crossing (GEC, λ, 2 SOPS GLAN): Equatorial angle from the Prime Meridian (Greenwich) to the location a groundtrack intersects the equator when crossing from the Southern to the Northern hemisphere....
View Full Document

{[ snackBarMessage ]}

Ask a homework question - tutors are online