Interesting question, in regards to update times, I would look at the following...
With ADS-C, there are two lines here, basically the ground system and the aircraft system.
The ground system sends instructions to the aircraft with a list of reports to send, and how often to send them. The system on the aircraft automatically replies, if it can. Depending on the ground system sophistication, it may request very frequent response.
The ground system receives the reports, and based on the vendor, will interpolate between the received data points. Current ATC designs are using more frequent update requests and fewer interpolations.
There are a number of contract type as well, Periodic (ie every 'x' seconds) Demand (ie report requested from ground system) and Event (ie crossing a waypoint, altitude change, and lateral deviation change)
Some ground systems will ask for other data as well, but the ac is not required as of yet to comply, there is Predicted Route Group (next +1 position), Earth Ref Group with track extrapolation (ground speed, vert rate), MET Group with wind/temp, and Intent Group for route conformance.
As noted above, there are some basic minimums, depending on the routes.
Last edited by underfire; 23rd October 2013 at 21:28.