Javad DELTAGNSS Receiver, Руководство оператора

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Pre-measuring Preparation
Collecting Almanacs and Ephemerides
Establishing a USB Cable Connection
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2.4. Collecting Almanacs and Ephemerides
Each satellite broadcasts a navigation message that includes the ephemeris parameters of the
satellite, the almanac, and various other information. The ephemeris parameters describe the
orbital motion of the satellite and are used to predict its location/trajectory. The almanac gives the
approximate orbit (course) for the transmitting satellite and all other satellites in the same system
only.
• GPS and GLONASS satellites broadcast ephemeris data cyclically, with a period of 30
seconds.
• GPS satellites broadcast almanac data cyclically with a period of 12.5 minutes;
GLONASS satellites broadcast almanac data cyclically with a period of 2.5 minutes.
If the receiver has an almanac, you can considerably reduce the time needed to search for and lock
on to satellite signals.
The receiver regularly updates the almanac and ephemerides and stores the most recent versions
in its Non-Volatile Random Access Memory (NVRAM).
1. Set up the receiver in a location with a clear view of the sky.
2. Turn on the receiver.
3. Wait for about 15 minutes while the receiver collects complete almanac and ephemeris
data from the satellites.
You will need to collect or update the almanac and ephemerides under the following
circumstances:
• If the receiver has been off for a long time.
• If the last known receiver position, stored in the NVRAM, is different from the present
position by several hundred kilometers.
• After loading a new OAF.
Note:
If 15 minutes have passed and the receiver does not lock on to satellites, clear the NVRAM. See
for details.
• After loading new firmware.
• After clearing the NVRAM.
• Before measuring.