The present invention includes a system for use in a vehicle for determining the terrain type in proximity to a vehicle. The system comprises a processor configured to receive primary output data from at least one vehicle-mounted sensor, and secondary output data from a secondary data source; and a data memory configured to store pre-determined primary data relating primary output data for the at least one vehicle-mounted sensor to a particular terrain type, and store at least one data set relating to one or more terrain types. The processor is configured to compare the primary output data with the pre-determined data to determine an indication of the particular terrain type corresponding to the primary output data, and compare the secondary output data with a data set corresponding to the indication of the particular terrain type.