Didar Zowghi from the University of Technology in Sydney writes:
Errors in requirements specifications can have a major impact on software costs. One estimate given states that 40% of requirements need rework during the course of the software development project
In our case, that means that:
waterfall process + remote geolocation = cock-up
We could probably refine that to
(waterfall process + remote geolocation) * tight deadline = almost certain cockups
Download the Zowghi report (a bit dry but highlights the issues around requirements engineering)