A system for generating a costmap for use in planning a path through an environment, the system including one or more suitably programmed processing devices configured to obtain a map of the environment, acquire traversal data indicative of an ability to traverse parts of the environment, for each part of the environment, calculate a traversal indicator indicative of the ability to traverse the part, the traversal indicator being calculated in a colour space, and colourise the map using the traversal indicators to thereby generate a colourised costmap indicative of an ability to traverse the environment, the colourised costmap allowing path planning to be performed.