 On 24 July 1839 he married Margaret Sibly, the daughter of James and Elizabeth Sibly of St Neot in Cornwall.During that year, Dixon, with assistant surveyors Granville Stapylton and James Warner, began a trigonometrical survey of Moreton Bay for the Government to facilitate free settlement.A baseline of was measured on (today's Harrisville, south of Ipswich) as a foundation for the triangulation.