Not sure where you live in Norway, but on Jan. 3rd In Oslo, (date of your posting), during most of the 24 hour period, there were some periods when only three of four sats were visible in that area. Six AM is one time.
However most of the time, there were around six to eight sats visible. Now, depending on where your antenna is mounted, some sats may be blocked. For example, mine is under the dash, so any sats behind me, blocked by my roof will not be shown; however, those to the front, sides and above will be picked up at different strengths.
(If you need to know an exact number of visible sats in a specific place at a specific time, PM me via this website. Just give me a few days to respond, so pick a date a week in advance. Also, let me know the closest large city in the country.)
GPS coverage does tend to be better in the USA at all times.
If you are receiving at least three sats, and your map has you off course, it almost has to be either:
the software of the unit, or the software of the MAP source. I believe your problem is the map software. Reason is, somewhere on my journey via the Internet, and researching Tele Atlas maps, and different company's websites in regard to Navigation units, I ran across some type of statement about the discs containing different internal operating software for the units that require a disc inserted at all times, versus a unit that loads the mapping software totally on a hard drive.