1. A method of determining a machine for operating at an actual site, comprising: establishing a three-dimensional geographical model representing the actual site; determining at least one operation characteristic relating to the operation of each of a set of machines in relation to the model; predicting at least one performance characteristic for each machine based on the at least one operation characteristic and at least one respective characteristic of each machine; comparing the predicted performance characteristics for each machine; and determining a target machine based on the comparison.