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)