one of the biggest problems in building a 3D world from data sources is alignment
- different data sources have different degrees of accuracy, projection conventions, etc.
which makes them not line up
it can be very difficult and time consuming to compare each of your data sources against
each other, to judge which source is responsible for the discrepancy, and which is closer
to the real world
ideally, you would use a single application to quickly check any sort of spatial data
against another, but that application doesn't exist
satellite/aerial imagery can be the most difficult to align properly, though it's a
little easier if it comes in GeoTIFF format
various solutions for comparing data, presuming that one doesn't have any
expensive software: