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Electronics

Stupid Chart Tricks? Page 3

Electronics January 2003
By Ben Ellison


Stupid Chart Tricks?
Electronics Q&A
   
 
 More of this Feature
• Part 1: Chart Tricks
• Part 2: Chart Tricks
• Electronics Q&A
• Gladiator Autopilot
• Northstar 958
• Icom M602 VHF
• Furuno Fax30

 Related Resources
• Electronics Column Index
• Electronics Feature Index

I've purchased a Maptech Digital ChartKit and am trying out RayTech charting software, but the resolution does not seem to be as good as with ChartKit's included viewer. R.S., via e-mail

The problem probably is that you have not enabled RayTech's "SharpChart" option. Follow this menu trail: File/Setup/System, then select the Performance tab, and finally check SharpChart. On my system that results in fine-looking images.

Your question brings up the important issue of "charting engines." Panning, quilting, and particularly zooming huge raster files is computationally challenging. For instance, digital charts are scanned at 254 pixels per inch; at one-to-one on a typical 70- to 120-pixel-per-inch monitor, they will look quite crisp as well as quite zoomed in. All chart viewers should look about the same in this mode (hard to tell with RayTech, since it doesn't have a distinct 100 percent or 1-1 mode). But, as you zoom out to, say, 3x, the software has to eliminate two out of three of those original pixels. Done without intelligence, the resulting image will get pretty raggedy, since the important text, shorelines, etc. are relatively thin.

Hence, we get the "SharpChart" or "CrystalView" or "whatever" options; every chart viewing program can employ algorithms to analyze the image, trying to drop truly extra pixels and retain distinct objects. It is traditionally a switchable option because it adds overhead to the already strained brain of your machine and can slow things down. Of course this is less of an issue with today's faster processors and large RAM banks. But, these sorts of charting engine solutions do vary from one program to another, and they are critical to happy operations.

Got a marine electronics question? Write to Electronics Q&A, Power & Motoryacht, 260 Madison Ave., 8th Fl., New York, NY 10016. Fax: (917) 256-2282. e-mail: PMYElectronics@primediamags.com. No phone calls please. 

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This article originally appeared in the January 2003 issue of Power & Motoryacht magazine.

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