Check for negative longitudes west

[karlmsmith]

A common mistake/misunderstanding is saying the units of longitude are "deg W" when negative values are given, when they actually should be units of "deg E" (or positive values). I think this comes from users used to seeing a negative longitude and automatically thinking that is (positive) degrees west, not fully appreciating that they are changing the numeric sign in the process.

So a check should be added for negative longitudes in units of degrees west, which is unlikely to ever happen. Either do this on the client side and add an "Are you sure?" dialog with some explanation (preferable), or mark the values as questionable.