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The Monte Carlo simulations have revealed that we need as many observations as possible at the stations with a good sky distribution, together with short intervals for the estimation of wet zenith delays and gradients. For example, if there are observations every 30 seconds, then estimation intervals of about 5 to 10 minutes for zenith delays and gradients (‘rapid gradients’) have proven to yield the best results in terms of baseline lengths and station coordinates.
Ongoing and future tasks:
In VieVS, source based scheduling (as originally suggested by Bill Petrachenko and Tony Searle at NRCan)
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has been implemented with the possibility of two or four sources open for observation at a particular time. The Vienna group
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has been testing how the results with this approach differ from using the classical station based scheduling as also used by SKED.
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Details are provided in the open-access Journal of Geodesy paper by Sun et al. 2014.
A preliminary evaluation has also been carried out on the impact of the cutoff angle in VLBI observations. Tierno Ros et al. (2013) have taken a 16-station network and they have created schedules
Figure 3 (from Tierno Ros et al. 2013)
Ongoing and future tasks:
- Source based scheduling with four sources observed at a time allows increasing the cutoff elevation angle. It should be assessed what is the benefit when using a higher cutoff elevation angle.
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J. Boehm, J. Wresnik, and A. Pany, Simulations of wet zenith delays and clocks, IVS Memorandum 2006-013v03, 2007.
Tierno Ros