On Mar 10, 2010, at 8:36 AM, Brian Rosen wrote: > I suppose that it's conceivable that every carrier, the FCC, NENA and APCO > are all stupid.
The 100 m/95% is a requirement, not an attempt to describe current GPS performance. As far as I know, the requirement was stated when GPS SA (selective availability) was still enabled. > > On the other hand, the carriers spend millions of dollars testing every > year. So, perhaps they aren't quite so stupid. I'm afraid I'm missing how this relates to my note. Did I accuse anybody of being stupid? > > I don't have access to the full paper to understand what a "20 minute field > test" is, but the largest problem for 100 meter 95% confidence is the fact > that the GPS is not always enabled (for battery drain reasons) and unless > it's on and seeing satellites for many minutes, you don't get really good > accuracy. Also, field tests are usually conducted in open sky situations, > and not urban canyons, or even tree leaf cover situations, which degrade > performance considerably. As an aside, this illustrates that the 95% number is pretty meaningless. Does it mean 95% of all calls (lots more emergency calls are made from indoors and the urban canyons of Manhattan than from open fields) or 95% of all sample points? Is it measured immediately after turning on the device or after waiting N minutes? Without such detail, making precise statements is just pretend-precision. Henning _______________________________________________ Gen-art mailing list [email protected] https://www.ietf.org/mailman/listinfo/gen-art
