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v5.8
GPS
The GPS receiver needs a certain time to obtain and structure the information that the satellites send. This time can be reduced
if there is certain prior information. This information is stored in the almanacs and ephemerides. The information that can be
found out is relative to the current position of the satellites (ephemerides) and the trajectory they are going to follow over the
next days (almanacs). The almanacs indicate the trajectory that the satellites are going to follow during the next days, having
a validity of some 2-3 months. The ephemerides indicate the current position of the satellites and have a validity of some 3-5
hours.
Depending on the information given to the GPS module, the start up can be divided into these types:
•
Hot Start: once the time and date are established and the
ephemeris
and valid almanacs are in the memory. Time:
~1s
•
Cold Start: without having established the time, date, almanacs or ephemerids. Time:
~35s
As can be observed, the start up time reduces greatly, particularly when
ephemerides are stored
. For this reason, some
functions have been created to
store ephemerides on the SD card and enable them to be loaded later
.
All information about their programming and operation can be found in the
GPS Programming Guide
available at the
of Libelium website.
All the documentation is located in the
in the Libelium website.
