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Bernese GPS Software Version 5.0 - Bernese GNSS Software

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11. Troposphere Modeling and Estimation<br />

Figure 11.1: Troposphere related options in <strong>GPS</strong>EST (1).<br />

11.4.2 Site-Specific Troposphere Parameters<br />

In addition to an a priori troposphere model, program <strong>GPS</strong>EST offers the possibility to set up<br />

and estimate so called site-specific troposphere parameters. These parameters are stationand<br />

time-dependent corrections to the a priori model and are represented in a piece-wise<br />

linear, continuous way (see Section 7.5.2). You will have to estimate these parameters in<br />

virtually all observation scenarios. For small networks where troposphere parameters are<br />

highly correlated between sites you have the possibility to estimate relative troposphere<br />

parameters with respect to the a priori model parameters of a selected station.<br />

Considering these corrections and the approximation in Eqn. (11.15) the total slant delay<br />

may be written in the form<br />

∆̺ i k (t,z) = ∆̺apr,k(z i k ) + ∆̺k(t)f(z i k ). (11.16)<br />

Option “Site-specific troposphere parameters” in panel “<strong>GPS</strong>EST 5.1: Setup of Parameters and Pre-<br />

Elimination 1” activates the estimation of these parameters. In panel “<strong>GPS</strong>EST 6.3.1: Site-<br />

Specific Troposphere Parameters 1” (see Figure 11.1) the user must select an appropriate map-<br />

ping function f(zi k ) and the desired time resolution (option “Parameter spacing”). The avail-<br />

able mapping functions are dry and wet Niell, cos z, and the Hopfield wet mapping function.<br />

In addition you may impose absolute and relative constraints (see Section 7.5.4). Usually a<br />

dry (hydrostatic) a priori model is used (e.g., DRY NIELL) with the estimated part mapped<br />

with a wet mapping function (e.g., WET NIELL).<br />

Note that 12 + 1 = 13 parameters per station will be set up if you choose a parameter<br />

spacing of 2 hours for a one-day session. This is due to the piece-wise linear representation.<br />

Figure 11.2 shows the second troposphere-specific panel in program <strong>GPS</strong>EST (“<strong>GPS</strong>EST 6.3.2:<br />

Site-Specific Troposphere Parameters 2”). The user may choose stations which should be excluded<br />

Page 246 AIUB

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