Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A principal positioning system for the Earth   The project SYPOR wishes to use the global navigation satellite system
GALILEO as an autonomous relativistic positioning system for the Earth.
Motivations and a sketch of the basic concepts underlying the project are
presented. For non geodetic (perturbed) satellites, a two-dimensional example
describes how the dynamics of the constellation of satellites and that of the
users may be deduced from the knowledge of the dynamics of only one of the
satellites during a partial interval.

13
The categories of this paper are: quant-ph
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The categories of this paper are: hep-lat
25
The categories of this paper are: patt-sol
2
The categories of this paper are: math
10
The categories of this paper are: q-bio
34
The categories of this paper are: chem-ph
15
The categories of this paper are: nucl-ex
3
The categories of this paper are: physics
23
The categories of this paper are: solv-int
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The categories of this paper are: math-ph
31
The categories of this paper are: ao-sci
8
The categories of this paper are: hep-ex
21
The categories of this paper are: adap-org
37
The categories of this paper are: supr-con
36
The categories of this paper are: cmp-lg
18
The categories of this paper are: econ