International hydrographic organization specifications for chart content and display aspects of ecdis
C.3 Verification of the display performance at sea
Download 0.98 Mb. View original pdf
|
S-52 Appendix 2 - IHO
| C.3 Verification of the display performance at sea C Calibration tests to be used for verification of display's performance onboard ship Colour calibration has traditionally been a complex and difficult task. Significant advances have been made in this area to achieve accurate results using instrumentation. This has been achieved by using modern photometric instruments to measure luminance, and ensuring that the monitor to be calibrated is well shielded from stray light entering the measurement area. Because instrument-based testing is still not practical as an ongoing test on shipboard, an alternate approach has been chosen. Specifically a "Greyscale Test" and an onboard "Colour Differentiation Test Diagram" have been chosen as subjective measures of the monitor's performance. C Greyscale test Greyscale is a well understood test pattern in the Video Monitor world, and it has a natural application here. The Greyscale testis a visual test that is used to determine the colour tracking of the monitor. It is general, it is non quantitative and requires judgement on the part of the operator to use. On the other hand, it is quite sensitive, and familiar to video technicians. This testis simple to use. It consists of putting a greyscale of at least 8 steps from black to white on the screen. The greyscale should be made of rectangles that are at least 2.5 cm by 10 cm. These can be oriented in either a horizontal or vertical direction. The greyscale is critically observed by the viewer from a distance of about 50 cm to 100 cm and any colour shifts in any of the rectangles of grey are noted. The greyscale should appear to be a neutral shade of white in all rectangles. Each should appear to be the same 'colour' as the others, even though varying in intensity from black to white. Colour shading in any of the rectangles indicates a problem in the adjustment of the display. |