A method of displaying a marker, comprising: receiving by a monitor apparatus comprising a display device a first video signal by a first video camera, selecting by a user a first position in a picture image associated with the first video signal, the picture image displaying the first video signal in a picture display mode on the display device; displaying a first marker at a second position, corresponding to extracted pixel data of the selected first position, in a vector image associated with the first video signal, the vector image displaying said first video signal in a vector display mode on the display device, placing an additional marker at the second position of said first marker on the vector image, switching the monitor apparatus from the first video signal to receive a second video signal by a second video camera, wherein the additional marker remains displayed at the second position, selecting by a user a third position in the picture image, said picture image displaying the second video signal in a picture display mode on the display device, displaying a second marker at a fourth position, corresponding to extracted pixel data of the third position in the picture image, in the vector image displaying the second video signal in a vector display mode on the display device, wherein the third position is selected such that the image portion at the third position in the picture image associated with the second video signal corresponds to the image portion at the selected first position in the picture image associated with the first video signal, thereby showing a positional relationship between the second position of the first marker and the fourth position of said second marker in the vector image displayed in association with the second said video signal. receiving by a monitor apparatus comprising a display device a first video signal by a first video camera, selecting by a user a first position in a picture image associated with the first video signal, the picture image displaying the first video signal in a picture display mode on the display device; displaying a first marker at a second position, corresponding to extracted pixel data of the selected first position, in a vector image associated with the first video signal, the vector image displaying said first video signal in a vector display mode on the display device, placing an additional marker at the second position of said first marker on the vector image, switching the monitor apparatus from the first video signal to receive a second video signal by a second video camera, wherein the additional marker remains displayed at the second position, selecting by a user a third position in the picture image, said picture image displaying the second video signal in a picture display mode on the display device, displaying a second marker at a fourth position, corresponding to extracted pixel data of the third position in the picture image, in the vector image displaying the second video signal in a vector display mode on the display device, wherein the third position is selected such that the image portion at the third position in the picture image associated with the second video signal corresponds to the image portion at the selected first position in the picture image associated with the first video signal, thereby showing a positional relationship between the second position of the first marker and the fourth position of said second marker in the vector image displayed in association with the second said video signal.