In the 1980s, scientists began using signals from Transit satellites and the early GPS system to precisely measure the shape of the Earth. They used equipment such as the Magnavox Terrain Navigator and the TI4100 GPS receiver on display in the Time and Navigation exhibition. Join geographer Andrew Johnston as he discusses the remote and inhospitable locations scientists often worked in with these devices and the enduring impact of satellite positioning on how scientists and surveyors work.

Meet at the Museum "Great Seal", in the Boeing Milestones of Flight Hall on the first floor.

About the Ask an Expert lecture series: Every Wednesday at noon in the National Mall Building, a Museum staff member talks to the public about the history, collection, or personalities related to a specific artifact or exhibition in the Museum.