Performance line display unit

A performance line display unit, comprising:

• an imaging device which is attached in proximity to a leading end of an extensible boom provided on a rotation platform rotatably placed on a vehicle of a crane;
• a display configured to display an image imaged by the imaging device, the image is imaged from above toward a hook block with the imaging device attached in proximity to the leading end of the extensible boom;
• and
• a performance line arithmetic part configured to obtain a first performance line regarding a suspended load maximum performance of a crane, wherein
• the performance line arithmetic part includes a coordinate position calculator configured to match a coordinate position on a real space and each position of the image by the imaging device,
• the performance line arithmetic part is configured to bring a position of the obtained first performance line in line with the coordinate position obtained by the coordinate position calculator, and overlap the first performance line with the image to be displayed on the display, so as to display an actual position of the first performance line on an actual image, and
• the performance line arithmetic part is configured to obtain a second performance line having a load rate lower than that of the first performance line, and to display the obtained second performance line on the image of the display together with the first performance line.