GNSS Satellite (GIOVE-A)

NAPEOS Features

The main features of the NAPEOS GNSS processing software are:

  • Process data from all GNSS systems
    • GPS
    • Galileo (tested with GIOVE-A and -B)
    • EGNOS
    • QZSS under development
    • COMPASS/BEIDOU will be developed as more information and data becomes available
  • RINEX data interface
    • Versions 2 and 3 supported
  • Follows the International Standards
    • IERS 2003 conventions
  • Undifferenced GNSS data processing
    • All clocks estimated
    • Allows for time transfer
    • Allows for precise point positioning
  • Integer ambiguity resolution
    • Double differenced ambiguities formed from the undifferenced ambiguities
  • By default NAPEOS processes the ionosphere free linear combination but it is also capable of processing single frequency code and phase observations.
  • NAPEOS is also capable of state of the art processing of SLR and DORIS measurements

NAPEOS Parameter Space

Parameters that may be estimated in NAPEOS include
  • Earth rotation parameters
  • Station positions
  • Station zenith delay parameters
  • Transmitter and receiver clocks
  • Intersystem biases (e.g. between GPS and GLONASS)
  • Carrier phase ambiguitites
  • Satellite orbits
    • State vector
    • Solar radiation parameters
    • Extended solar radiation parameters (from CODE) for the GNSS satellites
    • Dynamical parameters; once per revolution terms in radial, along, and cross-track
    • Drag parameters.
  • Satellite antenna phase centre offsets
  • Satellite antenna phace centre variations as spherical harmonics
  • Station range- and time-biases

Most parameters may be modeled as constant or as linear trend.

NAPEOS System requirements

NAPEOS runs on several different platforms using several different compilers. Below a list of working configurations:
  • SunOS using Sun Studio 11.
  • Several flavours of Linux:
    • SUSE
    • Ubuntu
    • CentOS
  • Compilers under Linux:
    • g95 (free)
    • gfortran (free)
    • Intel Fortran compiler (ifort, commercial but very fast!)
  • Apple using ifort compiler
  • Windows NT, XP, and Vista
    • using Unix like environment CYGWIN
    • Compilers g95, gfortran, or ifort

Note that the PosiTim NAPEOS service package includes the installation of the software on your computers. So do not worry if your preferred configuration is not included in the list below. We guarantee that we will get the software running on your system!

Besides a Fortran-90 compiler NAPEOS needs the tcl/tk software (including wish and expect). This is freely available software that is contained in most unix distributions.

The complete NAPEOS installation requires approximately 500MB. The memory requirements depend on the size of the networks you want to process. In NAPEOS the memory is allocated dynamically and thus depends on the size of your problem. A 100 station GNSS network solution requires approximately 2GB of RAM.


The user interface is based on the tcl/tk software package using "wish". It is very easy to use although some people consider the "look and feel" to be a bit old. Nevertheless it is easy to operate and learn. The automation is based on the same software package using "expect". The automation is a very powerfull tool of the NAPEOS GNSS processing software.

NAPEOS Software Requirements

NAPEOS requires the following software, that is not included in the delivery, to operate :

  • Basic UNIX tools:
    • sh (Bourne shell)
    • csh (C-shell)
  • tcl/tk package (available for practically all UNIX systems)
    • including wish (normally included with the tcl/tk)
    • including expect (not included by default but available as optional extra with the tcl/tk package)
  • Fortran 90 compiler
    • Sun Studio on Sun Solaris
    • gfortran, g95, or intel fortran (ifort, commercial), on Linux
  • GNU Make to compile the source files using the NAPEOS make files
  • BLAS and LAPACK linear algebra package
    • Available with most compilers
    • Alternatively one can download the software from
      • BLAS
      • LAPACK
  • For the basic, and optional, graphics functions in NAPEOS the pgplot package is required.
    • Web adress:
    • Download from: