Boxkite wrote:PaulSS, what stops PA displaying both a bearingless ring received directly from an aircraft and a multilaterated signal from an OGNR station for the same aircraft?
Its quite complicated but effectively we are processing data from 2 sources, the transponder direct, and the transponder indirect (via OGN-R)
Both of these sources have the same HexID, and each have individual timestamp information indicating how recent there specific data was captured.
If the timestamp exceeds a threshold the data is discarded as no longer relevant.
So here is a typical scenario that we see.
An aircraft on approach to an airfield gradually descending, at some height threshold, the MLAT network does not receive sufficient information to resolve a position. For example, at Coventry Airport, this happens around 500ft AGL.
Once the MLAT capture times out, PilotAware only has the ModeS data, and hence reverts from a positioned aircraft to a bearingless target, using the known altitude, and signal strength resolution as per classic Bearingless Target resolution.
So in answer to your question, the two sources of data are combined, but the visual and audio representation is based upon the timely relevance of the data.