A method for training an environmental analysis system, the method comprising: receiving a data model of an environment; forming, in dependence on the data model, a first training input comprising a visual stream representing the environment as viewed from a plurality of locations; forming, in dependence on the data model, a second training input comprising a depth stream representing depths of objects in the environment relative to the plurality of locations; forming a third training input, the third training input being sparser than the second training input; and estimating, using the analysis system, in dependence on the first and third training inputs, a series of depths at less sparsity than the third training input; and adapting the analysis system in dependence on a comparison between the estimated series of depths and the second training input.