International hydrographic organization specifications for chart content and display aspects of ecdis
Download 0.98 Mb. View original pdf
|
S-52 Appendix 2 - IHO
| ANNEX B PROCEDURE FOR INITIAL CALIBRATION OF COLOUR DISPLAYS (Note that the specifications in this Annex are generally applicable to all types of monitors. Some sentences which apply only to CRTs are in italics) _________ B.1 Introduction Calibration is required to transform the CIE coordinates of these specifications into RGB values that apply to the particular monitor used by the ECDIS manufacturer. Note that the primary aim is to reproduce the colour distinctions needed to distinguish between different features on the display. Accurate absolute colour matching between different monitor's is not required. Calibration defines the monitor performance in terms of the relationship between input signal and the colour and luminance output on the screen. This is performed for each of the red, green, and blue (R, GB) channels. The signal that drives the CRT monitor is specified in terms of three DAC (Digital to Analog Converter) values - one each for R, G, and B. These are usually from 0 to 255, and colour is specified in CIE coordinates of x-y, and luminance (Lin candelas per square metre. The DAC values are programmed within the image generator to generate specific colours required by the system. Calibration consists of two parts - measurement of the monitor colour characteristics and data processing to generate the transform between CIE colour coordinates and RGB inputs to the monitor. A comprehensive calibration of the monitor is required upon initial use. In case the monitor colours deteriorate after extended use at sea, two further capabilities are necessary 1. A means of detecting when the colour calibration has deteriorated to the extent that the colour distinction on the display is lost. This is described in Annex CA method of restoring the original colour distinctions. This is not yet developed. Download 0.98 Mb. Share with your friends:
|