The theodolite and radio set used to establish position.

"We had to have the means of getting our position independently at any time. So Craig borrowed a theodolite to take latitude and local time by observing the altitudes of stars, and Giblin produced a short-wave wireless receiver to get Greenwhich time, so that longitude could be found from local time. The receiver was packed in a padded box bolted to his car."

(R.A. Bagnold, Lybian Sands, London, 1935)