GPS Receiver User's Guide E-705

Rikaline
Rikaline Marketing Corp. 5F-1, 125, Roosevelt Road, Sec. 5, Taipei, Taiwan 116
Tel: ++886 2 2934 5456 Fax: ++886 2 2934 4373 E-Mail: [e-mail]
web: www.rikaline.com.tw
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2. Operational Characteristics
2.1 Initialization
As soon as the initial self-test is complete, the E-705 begins the process of satellite acquisition and
tracking automatically. Under normal circumstances, it takes approximately 40 seconds to achieve a position fix,
15 seconds if ephemeris data is known. After a position fix has been calculated, information about valid position,
velocity and time is transmitted over the output channel.
The E-705 utilizes initial data, such as last stored position, date, time and satellite orbital data, to achieve
rapid GPS signal acquisition and fast TTFF. If significant inaccuracy exists in the initial data, or the orbital data
is obsolete, it may take more time to achieve a navigation solution or cold–start automatic-locate will be invoked.
However, acquisition performance can be improved significantly of the host initializes the E-705 with a rough
estimate of time and user position.
2.2 Navigation
After the acquisition process is complete, the E-705 sends valid navigation information over output
channels. These data include:
1) Latitude/longitude/altitude
2) Velocity
3) Date/time
4) Error estimates
5) Satellite and receiver status
The E-705 will perform 3D navigation when 4 or more satellites are tracked. When 3 or fewer satellites are
tracked, altitude-hold is enabled using the last computed altitude and 2D navigation mode is entered.
With signal blockage or rising and setting of the satellites, where a change in satellite constellation used for
position fix occurred, large position error may result. The E-705 incorporates a proprietary algorithm to
compensate the effect of satellite constellation change, and maintains an accurate smooth estimate of the
receiver’s position, velocity, and heading.