Sandby is best known for his topographical and picturesque landscapes in watercolour. He probably learned drawing from his brother Thomas, and like him became a military draughtsman for the Board of Ordnance at the Tower of London. In 1747 Sandby was appointed chief draughtsman to the Military Survey in Scotland, established in the wake of the Jacobite rebellion of 1745. Based in Edinburgh, where he taught Robert Adam drawing, he travelled throughout the country producing detailed maps for the army and painting both topographical and picturesque views. In 1768 he became a founder member of the Royal Academy, London.