Bernese GPS Software Version 5.0 - Bernese GNSS Software

11.6 Remarks and Hints on Troposphere Estimation
11.6 Remarks and Hints on Troposphere Estimation
Let us close the troposphere chapter with some general remarks and recommendations
concerning the troposphere estimation in the Bernese GPS Software:
(1) It is recommended to always estimate site-specific troposphere parameters. Usually
the dry part of the troposphere is accounted for by the a priori model (DRY NIELL)
and the remaining wet part is estimated and mapped with an appropriate function
(WET NIELL). A time resolution of 1 or 2 hours is reasonable for standard analyses.
(2) The only exception to the previous point are “rapid static” scenarios with short observation
times (below 1 hour). In this case it may be best to just use an a priori
model (NIELL) to account for both, the dry and wet part, of the troposphere.
(3) The estimation of horizontal troposphere gradients is recommended, even in small
networks. An exception may be the processing of single baselines. Usually the time
resolution for gradients is much smaller than for zenith path delay parameters (e.g.,
one set of gradients per day). For the estimation of reasonable gradient parameters,
data gathered at low elevations is absolutely essential.
(4) The use of low elevation data (below 10 o ) is strongly recommended to decorrelate
troposphere estimates and station heights (particularly in small local campaigns).
(5) For parameter intervals longer than, let us say, 1 hour, it is usually not necessary to impose
relative constraints. If kinematic coordinates are estimated relative troposphere
constraints may be necessary also for longer time intervals.
(6) For small local campaigns it makes sense to estimate troposphere parameters for all
but one station (due to strong correlations between the troposphere parameters of the
stations included). Another possibility is to absolutely constrain the parameters for
one station.
(7) If tropospheric delays from global solutions are available for some stations (e.g., from
CODE, see input files in previous section), it may be a good idea to introduce these
values in your processing and estimate troposphere corrections only for the remaining
stations. When making consistent use of the CODE coordinates, orbits, Earth
orientation parameters, and troposphere estimates for the IGS stations included in
your network, you are able to get results that are almost identical to those you would
obtain by processing your (local) network data together with the global data set. 1
Of course the few points above are generalized and not universally valid. As always it is left
to the user to figure out the options which work best for his needs.
Consult Section 7.7.2 for a description of the troposphere handling for the processing of
SLR observations.
1 Since GPS week 1400 (2006-Nov-05; day of year 309) CODE is using the GMF (Global Mapping Function;
see [Boehm et al., 2006]) for its processing. Because GMF is not available in Version 5.0 of Bernese GPS
Software it is not possible to introduce CODE troposphere estimates after this date.
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