Nautical chart display device, nautical chart display method, and nautical chart display program

The purpose is to provide a nautical chart display device which enables a measurement of a distance on an electronic nautical chart, like a measuring method which is performed by using a divider. The nautical chart display device includes a display unit, an operation detector, a registration processing module, and a change processing module. The display unit has a screen and displays a nautical chart on the screen. The operation detector detects a touch operation to the screen. The registration processing module accepts two points of the touch operation on the screen, and registers a scale at which a distance between the touched points on the screen matches a distance setting on the nautical chart as an additional scale. The change processing module changes the scale of the nautical chart to the additional scale.