A device is disclosed for generating navigation instructions for display on a display device of a portable navigation device, comprising: means for accessing a repository storing digital map data pertaining to a navigable network along which the navigation device can travel, the digital map data including data pertaining to available lanes of the navigable network; means for generating, for display on the display device, a three-dimensional perspective view of a model representative of the map data as though from a camera positioned at an elevation and pitch angle behind a current position of the portable navigation device, that is updated to follow the device as it travels along a planned route, wherein the three-dimensional perspective view shows the available lanes of the navigable network, and wherein the planned route to be followed is shown in the view as a line, the line showing the route to be followed as passing along a determined current lane in which the device is travelling; and means for adapting the generated view, in response to detecting that the determined current lane in which the device is travelling differs from a lane or lanes associated with a manoeuvre to be made at an upcoming decision point in order to follow the planned route, such that the line showing the route to be followed indicates an instruction to the user to change lanes. Methods of operation of the device, and related computer software, are also disclosed.