International hydrographic organization specifications for chart content and display aspects of ecdis
particularly on an ageing CRT. Because good quality neutral filters reduce
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S-52 Appendix 2 - IHO
| voltages, particularly on an ageing CRT. Because good quality neutral filters reduce illumination without significantly affecting colour, and even tend to enhance contrast their use is recommended for the night display. 4.2.3 Display calibration and verification The ECDIS display should be calibrated initially in order to transform the CIE colour table coordinates to screen coordinates The main components of the ECDIS display are the monitor and the image generator. Both the monitor and the image generator used to drive the ECDIS display can be calibrated together as a colour generating unit. Another alternative is to calibrate separately both the monitor and image generator. This process is described for CRT screens in Annex Band software for processing calibration and converting CIE colour coordinates to RGB, with worked examples, is included in the Presentation Library. The ECDIS display calibration should be verified for type approval of all monitors as described in section 5.2.3, using a combination of instrumental testing for the bright sun colour table and subjective visual checking for the dusk and night colour tables. 42 S, Edition 6.0 March 2010 The procedure of calibrating all three colour tables by the current method used for CRTs, together with remote control of the calibration settings, should be used also for LCDs. The visual checking is done by viewing all but the bright sun colour table on a multipurpose Colour Differentiation Test Diagram carried in the Presentation Library and described in section 5.2.5 and the Presentation Library, Part I, section 19.4. The test diagram is also intended for use by the mariner for checking display performance and adjusting the controls as described below. The colour performance of the display will deteriorate with age. The principal effect is overall loss of luminance (candlepower. Fora CRT type of monitor this reduces the effectiveness of the bright sun colour table and may cause some colours of the night tables to drop below the cutoff point if cathode current stabilisation is not used. If at the same time relative luminance changes between the R,G & B guns should arise , colour reproduction will suffer and some distinctions between features maybe lost. The night display is the most vulnerable. Self calibrating CRT type of monitors, generally using a detachable sensor to measure the white light emitted by the CRT and feedback any necessary corrections to RGB values through software, are available from manufacturers such as BARCO. Other methods of detecting and eventually correcting for colour drift are being investigated, and are discussed in Annex Ci Colour control contrast and brightness controls There area variety of technologies available for monitors to be used for ECDIS display. Different technologies have different methods to control colour, contrast and brightness, but some basic rules apply for all of them. 4.2.4.1 Effect of controls. The contrast control of a display generally shortens or extends the range of luminance available, making the display appear darker or brighter. On the other hand, the brightness control shortens or extends the range of colour saturation available by adding white (which extends the range by making colours other than black less saturated, or subtracting white (colours become darker, more saturated.) To the viewer, it has much the same apparent effect as contrast, but it achieves this by altering the colour contrast of the colour tables between foreground and background colours, and this may result in some features becoming harder to see, Download 0.98 Mb. Share with your friends:
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