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# Coordinates Computation from Almanac Data

Fundamentals
Title Coordinates Computation from Almanac Data
Author(s) J. Sanz Subirana, J.M. Juan Zornoza and M. Hernández-Pajares, Technical University of Catalonia, Spain.
Level Basic
Year of Publication 2011

The almanac data allow to compute a raw estimation of the satellites coordinates (1-2 km 1 − σ error), which is needed for signal acquisition by the receiver.

The almanac data consist of a reduced set of parameters (with respect to broadcast ephemeris), as it is shown in table 1 for GPS satellites. Similar data is broadcast for Galileo.

Table 1: GPS broadcast almanac parameters.

Thence, the same equations as in article GPS and Galileo Satellite Coordinates Computation can be used to compute the coordinates from almanac, just taking:

$\Delta n ={\stackrel {\centerdot} i}= C_{uc}=C_{us}=C_{rc}=C_{rs}=C_{ic}=C_{is}=0 \qquad \mbox{(1)}$
and
$i=54^o+\delta i \qquad \mbox{(GPS satellites).} \qquad \mbox{(2)}$