Hi,
Unfortunately it isn't as simple as just importing from Google Maps. The technical specification for the world models is at https://www.bridgecommand.co.uk/Doc/WorldFileSpec.php, but I am making some of the technical requirements easier (not needing exact sizes for the heightmaps etc).
As an overview, you need a heightmap. This combines the land and underwater heights, generally a greyscale image. For the land elevations, there is now a fair amount of information available, for example the Tangrams heightmapper (https://tangrams.github.io/heightmapper/). Bathymetry data is generally harder to find, but for the Venice Lagoon (which I think is your area of interest), it looks like there is a good survey at https://www.marine-geo.org/tools/search/Files.php?data_set_uid=23605
These would then need to be combined into a single heightmap, containing the above and below water elevations, and you then tell Bridge Command about the Lat/Long of the South West point, as well as the size in decimal degrees (East/West and North/South).
Land objects (churches etc) can be added from their lat/long positions, as well as buoys etc.
I'm very happy to guide you through the process and help, but this would be over the next weeks/months, rather the next few days. I'm also actively working on making the world model building process simpler, as it is probably the most complicated part of using the program.
James
