Specifications

VP ONCORE COMMAND REFERENCE
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EPHEMERIS DATA OUTPUT MESSAGE (@@Bi)
This parameter determines the rate that satellite ephemeris data is
output. The user has the option of requesting the ephemeris data output
one time (polled), or each time the satellite ephemeris data changes
(continuously). The commanded satellite ephemeris data output rate is
stored in RAM and is retained between power cycles if backup battery
power is applied.
Ephemeris data for each of the GPS satellites is contained in subframes
1, 2, and 3, words 3 through 10. Each satellite transmits the ephemeris
data for itself only. The user is directed to the ICD-GPS-200 for specifics
on the format of the ephemeris data.
When polled, the VP outputs a complete Ephemeris Data Output
Message for each of the satellites that the receiver is currently using for
position fix. When continuous output is requested, the VP outputs the
current ephemerides once for all satellites currently tracked, then outputs
individual channel ephemerides again any time the ephemerides on that
channel change.
The GPS receiver outputs the ephemeris data through a series of output
messages, each of which corresponds to a particular satellite. The data
fields of each message correspond to words 3 through 10 of subframes 1
through 3 as defined in ICD-GPS-200. Each word contains 24 data bits.
The GPS receiver will output about 750 bytes of message data for each
one-second output opportunity. If selected, the ephemeris response
message is output for each satellite that is currently tracked until the total
number of bytes sent during a one-second epoch exceeds 750. The
remainder of the ephemeris message is sent during the next one-second
epoch (up to the 750 byte limit per second) until all of the ephemeris data
for all satellites is output.
91 Synergy Systems, LLC 05OCT01