Bernese GPS Software Version 5.0 - Bernese GNSS Software

17. Data Simulation Tool GPSSIM
The string SIMULA is automatically prepended to the receiver name to indicate simulated
data (necessary for the baseline creation program SNGDIF). The receiver name (including
SIMULA) must be defined in the “Receiver information”-file. The antenna type must be listed
in the “Phase center offsets” file.
The first option group in panel “GPSSIM 3.2: Simulation Options” defines the desired sampling
rate, the minimum elevation and the maximum number of simultaneously observed satellites.
The “Maximum number of observed satellites” may be set to the total number of channels of the
receiver. The simulator starts to track the satellite with highest elevation if a channel gets
free.
17.5 Troposphere Modeling
Basically the troposphere modeling is identical with that in GPSEST. Three types of modeling
the tropospheric delay for terrestrial stations are possible in GPSSIM:
• Specifying a model in “ZPD model and mapping function”. The selected troposphere model
is used to compute the troposphere delay with extrapolated meteorological data based
on a standard atmosphere. Option NONE deactivates the use of an a priori model.
• Introducing “Est. troposphere val.” in panel “GPSSIM 1: Filenames”. The option “ZPD
model and mapping function” will then be ignored. If a station is missing in this file the
tropospheric delay is computed based on the model specified in the input file (with
standard atmosphere).
• Selecting “Meteo data files” (one for each station) in panel “GPSSIM 1: Filenames”. The
tropospheric delay values are computed using the data from the files as input values
for the model selected in option “ZPD model and mapping function”. Extrapolated
meteorological data are used for all stations without meteo data in the input files.
If the same troposphere modeling settings are used in program GPSEST as for the simulation
it is expected that the estimated troposphere parameters are zero, or, in other words: it is
not necessary to setup troposphere parameters, at all.
17.6 Ionosphere Modeling
The deterministic part of the ionosphere may be applied to the simulated observations
by specifying a global ionosphere model in option “Ionosphere models” in panel “GPSSIM 1:
Filenames”. Alternatively night time and day time electron content of a very simple single
layer model (layer height=350 km) may be specified. The number of electrons E in the layer
is a function of local time only:
Tloc = UT + λ
⎧
⎨
E =
⎩
E0 for Tloc ∈ 〈20h ,8h
〉
Tloc − 14
E0 + E1 cos π for Tloc ∈ 〈8h ,20h 〉
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