It then combines this real-time information with ephemeris data, mapping, cellular base station and Wi-Fi access point database information, and other cloud-based aiding information using the SiRFusion platform.

ENGADGET: CSR sharpens indoor and in-car navigation with SiRFstarV, SiRFusion and SiRFprimaII

One of the lightest things you can carry is an app, and his favourite is the Photographer's Ephemeris, because it helps you plan the perfect outdoor shoot, with time-specific details about the position of the sun and the moon, such as when and where the moon is likely to rise over a particular hill.

BBC: Pro photographers reveal their top travel gear