A question for the piksi users:
I'm using a piksi GPS on my pixhawk quadcopter. I'm just using single precision now, while I wait for RTK to be enabled on Arducopter.
The problem is, the hdop is terrible! It usually hangs around 13, and sometimes gets as low as 6. The GPS health arm is constantly on.
Meanwhile, my other aircraft with a ublox GPS is sitting on an hdop of 1.x.
I put on the external antenna, it didn't help much.
I used an aluminium foil ground plane too.