I spent a number of years in mapping, global reconcillation of pre-WGS84 ellipsoids and datums with post GPS unification, national mapping projects etc.<p>There are many map arcana tales, yet <i>another</i> reason for "trap streets" - fake data infill, is to realistically fill voids left by top secret classified national security areas.<p>The UK Ordnance Survey famously produced rich detailed maps across all of the United Kingdom .. save for blank voids over naval shipyards, weapons testing, secret nuclear bunkers, etc . . .<p>Eventually somebody cottoned onto the reason these voided areas became magnets for Russian agents - nothing signified something of great interest.