> I don't understand this. As far as I know, the satellite basically sends its identifier and precise time, and from this information (combined with the information in GPS calendar that tells the locations of the satellites) the recipient can determines its own location.

I'd assumed the GPS calendar was somehow broadcasted by the GPS network too.

> Were you proposing to assume the location of a 5m sphere the recipient is in?

I guess the proposal was to change the problem from pinpoint a single point in space, to figure out roughly where I am, in which case being anywhere in a tiny sphere is pretty much the same as being in a point after you account for errors.