[mmaimcal] dgps specs

[Simon Radford]

During the Euro-meeting last week, the site group identified the
upcoming need for higher accuracy configuration layout on Chajnantor.
These days this means some sort of enhanced (differential) GPS system.
Darrel and I spent todday  speaking with vendors at a surveyors' trade
show. There are a wide variety of available GPS systems, with
corresponding ranges of capabilities and prices. To intelligently choose
between these systems, we must specify the necessary accuracy (dekam, m,
decim, cm, or mm), whether post-proceesed positions are adequate or if
we need real-time readouts, and a few other parameters.

Please send me your thoughts on these requirements. What parts of the
project require survey information? What are our surveying needs in the
D&D phase? During construction? How much surveying should we do
in-house?

Thanks,  Simon