1. A method of determining alarm conditions of a slope under inspection, the method including the steps of: (i) calculating one or more dimensionless threat estimate values for each of one or more time periods; (ii) selecting a maximum dimensionless threat estimate value from the one or more said dimensionless threat estimate values calculated in (i); (iii) comparing the maximum dimensionless threat estimate value with a threshold alarm value; and (iv) setting alarm conditions if the maximum dimensionless threat estimate value exceeds the threshold alarm value.