Originally Posted by codprawn
What makes no sense? Isn't it obvious that you can't squeeze a detailed map of the whole USA into a small amount of memory - it's a pretty big place!!! I have detailed maps of the Uk and they take up over 20gb!!!
You're doing it again, Codders. Here is a pic of Bluechart coverage for the northern part of Britain and also a pic of the size of memory needed to accomodate the maps. If we guess that the southern half of Britain will need approximately the same amount of memory then that's a total of far less than 30meg. If the Etrex has 50meg of memory as has been mentioned there will be some to spare even if the whole of the UK Bluechart is loaded.
Whilst a base map of the US is of little use in the UK, a base map of your country without the Bluecharts is still pretty useful. Although the base map doesn't contain detailed information, if you have a paper chart it's possible to place waypoints and build routes in the plotter. You can then use the plotter for navigation in the usual way because the base map will be accurate to a half mile or so. Fine detail can be got from the paper chart. Bear in mind that electronic chart detail is not as fine nor as complete as paper chart detail.
This technique is particularly useful if you travel outwith your chart plotter chart coverage because you can usually source a paper chart of local and adjacent areas in a chandlery.