Abstract: A computerised method of generating a first trainable transform arranged to be used in localisation of an entity, the transform being arranged to transform a first representation of an environment to a second, different, representation of the environment, the method comprising processing a plurality of first training representations of an environment using the first trainable transform to generate a transformed first training representation; performing at least one of: i)) running at least one known process on the first training representation and a modified version of the first training representation to generate an error signal where in the process is selected such that the first trainable transform is arranged to enhance features within the first training representation; and ii) running at least one known process on a second training representation, corresponding to the first training representation, but under a different lighting condition, and on the modified version of the first training representation