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Satellite Ephemeris:
GPS satellites orbit information. According to ephemeris, satellite
positioning signal and time, the current location can be determined. Ephemeris need to
download from the GPS satellites, but the download speed is very low (approx. 50bps),
and vulnerable to the impact of satellite signal strength. The high bit error rate may lead to
a longer time of download ephemeris, and even download fail. The sound level meter can
keep the ephemeris data in memory for approx. 30 minute after turn off GPS module. The
ephemeris data is only is valid within 2 hours.
Satellite Signal Noise Ratio:
Satellite positioning signal intensity. In rainy days or indoor,
signal strength will be affected.
GPS have 3 boot modes: Cold start, warm start and hot start
Cold Start:
First location, need to download the latest ephemeris and longer time.
Warm Start:
GPS module has the last saved location information, but need to
re-download the ephemeris due to expired. Warm start needs almost same time as cold
start.
Hot Start:
GPS module has valid ephemeris and can reposition in a very short time.
PCE-428 / 430 / 432
