Tried to find an old paper (with no luck) that suggested that small sky view could still produce a good fix with low horizontal errors.
Cannot remember what they said about vertical errors.
With the current 31 operational GPS satellites I believe you can get low error positions with less than 50% skyview.
Certainly observation in commercial jets thru a very small window suggests you can get good postions with signifcantly less than this.
Yes, a good spread of satellites is required but with 31 operational this is only rarely not available.
I have never opened a SkyEcho but some reported issues surprise me.
Its odd when good quality GPS receiver/antennas can be purchased for less than US$15.
Tried to find the GPS specs but they do not even quote the number of channels.
Pulled out an old car GPS (Garmin Nuvi 50) from 2012 with 12 channel receiver.
This is in my front yard with 30 degree shading to the north, 20 degree shading to the east and west and -20 degree to the south (yes I am on a hill).
By shading I mean from horizon to say 20 above horizon is not visible to the receiver.
At my home in northern suburbs of Sydney I am receiving 10 satellites and it is indicating a horizontal error of 4m.
The only time I have seen large errors in the last 10 years is when driving thru the Sydney CBD.