Motorola M12 Oncore User's Guide download pdf (Page 20)

Chapter 3 – Receiver Description

Motorola GPS Products - Oncore User’s Guide

RF Jamming

Immunity (continued

Test results have demonstrated that this approach is effective at providing an

additional 10 dB of jamming immunity both in the GPS band and out-of-band. The

combined results of the additional filtering and the adaptive tracking loops in the UT

Oncore make it very effective at improving RF jamming immunity, thus making

installation in timing applications more flexible and robust.

AUTOMATIC SITE SURVEY (UT MODEL ONLY)

The Automatic Site Survey mode simplifies system design for static timing

applications. This automatic position determination algorithm is user initiated and can

be deactivated at any time.

The Automatic Site Survey averages a total of 10,000 valid 2D and 3D position fixes. If

the averaging process is interrupted, the averaging resumes where it left off when

tracking resumes. During averaging, bit 5 of the DOP type field in the

Position/Status/Data Message (@@Ea) is set. Once the position is surveyed, the UT

Oncore automatically enters the Position-Hold Mode. At this point, the auto survey

flag is cleared and the normal position-hold flag is set in the receiver status byte of

the @@Ea message. Once the antenna site has been surveyed in this manner, the

user can expect a 2D position error of less than 10 m with 95% confidence and a 3D

error of less than 20 m with 95% confidence.

Throughout the survey time the Time RAIM algorithm is active (if enabled) and is

capable of detecting satellite anomalies, however isolation and removal of the bad

measurement is not possible. Once the survey is completed, the Time RAIM algorithm

is capable of error detection, isolation, and removal.

The status of the Automatic Site Survey and Position-Hold Mode is retained in RAM

when the receiver is powered down only if battery backup power is provided.

Revision 5.0 08/30/02

3.20

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Motorola M12 Oncore User's Guide Page 20