The OpenWorldTemporalMap is OpenStreetMap with a temporal aspect. That means view a current map of the world as it exists at any certain time in the history of civilization (that seems like a good starting point in time. :) ). This doesn't actually exist but it seems like a pretty awesome concept. I am putting this page up for brainstorming about the possibilities.
Browse to OpenWorldTemporalMap, see map at default point in history. User then browses the map to see the current map by both point in history and by location.
The user might first look at Manhattan Island in 1800, then browse to Rome in 500 AD, then to modern day Rome. She then jumps to Manhattan at the present time, then to Manhattan five years in the future.
The user observes the Confederate States of America starting in 1861 and continuing to 1867 where they no longer exist.
The user navigates to Giza in 2492 BC and then continues to navigate forward and back in time to watch the development of pyramids, worker's villages, cemeteries etc.
The user is curious about when a modern day highway was built. He finds the highway in the present day, then navigates back in time until the highway doesn't exist yet or is under construction.
The user navigates to 1450 AD and looks at the map of Tenochtitlán first and then navigates south to Machu Piccu.
Potential default time points in history
The time the user views the map. The time when the first known map in history was made. This list could get really interesting...
Possible benefits to OpenStreetMap
OpenStreetMap becomes focused only on geographic features as they are observable on the ground right now in the present day. No need for discussions about whether to map historical roads or railways of which one can no longer find any trace.
Data that would be needed
If a user adjusts a street in OpenStreetMap, did the user correct an innacurate location or did the location of the street change? Those two possibilites affect temporal map data differently. The first should change historical data for that street as well. In the second case, the map for the point in time just before the edit should continue to display the original data, since that is where the street is at that point in time.
If a certain highway changes from primary to motorway (or track to secondary, etc), at a certain point in time, that must be noted (as temporal data (start-end dates) for the tag?)
At Beyond The Big Dig (Boston.com) there exists a history tab on the interactive map which shows landfill in and around Boston. There is a time slider which is similar to my idea in this page.
Google Maps' Earth Engine includes a timelapse visualization of satellite imagery changing over time.
I know I'm probably not the first to have this idea. So I'll try to collect similar pages here to share the wealth!
I found these links recently when wondering about this:
There is also a proposal page somewhere with a similar idea, I should find it and add the link to it.