1. past tense of heliograph; transmitted a message using a heliograph (a device that reflects sunlight to send signals over long distances)
Usage: historical/technical; primarily military or surveying context
2. past tense of heliograph; created a photographic image using heliography (an early photographic process)
Usage: historical/technical; photography and printing

Examples

• The soldiers heliographed messages across the desert using mirrors and sunlight.
• During the survey, the team heliographed coordinates to the distant observation post.
• The engineer heliographed the architectural plans onto a metal plate using early photographic techniques.
• Before radio communication, military units heliographed urgent orders across mountain ranges.
• The photographer heliographed the landscape onto a copper surface in the 1820s.