Nav Canada deploys sat. aircraft tracking for Hudson's Bay (ADS-B)

[JF Mezei]

http://www.navcanada.ca/NavCanada.asp?Language=en&Content=ContentDefinitionFiles\Newsroom\Backgrounders\ads_b.xml


Hudson's Bay was a dark hole without radar coverage, requiring much
greater aircraft separation.

Aircraft will need to be equipped with a satellite transponder and
ground will then have a full picture of traffic over the region.

What I don't understand however is why they would need some ground
stations around Hudson's bay for this. If aircraft report their
positions/altitude to a satellite, wouldn't the satellite just beam that
info back down to the Nav Canada control centre ?

Or are those stations needed for VHF voice communications with Nav
Canada controllers ?

Is this the same type of system used over the south pacific ?

And more importantly, if Nav Canada is equipped to handle this, how come
it would be narrowed to just one region and deployment to other regions
later on ? Wouldn't the satellites be able to tracks aircaft anywhere
over canada ?
.
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[Roland Perry]

Post by JF Mezei
What I don't understand however is why they would need some ground
stations around Hudson's bay for this. If aircraft report their
positions/altitude to a satellite, wouldn't the satellite just beam that
info back down to the Nav Canada control centre ?

Surely you don't think GPS works by sending your position to a
satellite?

This ADS-B system seems to be a fairly crude way of aircraft
transmitting their position (obtained by GPS) to some VHF receivers on
the ground, which then send the report back to air-traffic-control so
they know where the planes are.