"Dead-reckoning" is a navigational term used to describe the process of calculating one's current location by comparing last-known location to estimated time elapsed and trajectory of the vessel.
It's about as accurate as it sounds. When a boat is lost at sea without navigational tools or the ability to see the stars, then dead-reckoning is all you have. It has resulted in many a sunken ship.
This happens in missions. When captains of ships rely solely on previous known locations in order to guesstimate a course of action, the results are usually less than ideal. In the same way, missionaries who rely on past experience in past contexts to develop strategy, it will often fall short.
Two things are absolutely crucial for effective cross-cultural engagement.
Biblical Foundation. The missionary must search the Scriptures for clarity and guidance in the missions endeavor. It is the message and the manual for followers of Jesus taking the gospel to new cultures.
Clarity of Context. As missionaries seek to apply biblical principles and communicate the biblical message, they must allow the local context to give shape to strategy and forms of communication. Each context is different.
There are constants, but they are always in context. The faithful missionary begins as a student, and remains a student. It is only by studying the Scriptures and the context that strategies that are biblically faithful and culturally relevant can be developed.
Dead-reckoning is poor mission strategy.