Julian Foad writes:
>
> Norman Vine wrote:
> >
> > vmap0 can be off by ~500 meters and still be considered
> > accurate since it is 1:1,000,000
>
> Every time I see a map scale ratio like "1:100" for digital mapping data, I am
> confused. For a paper map it means "1
> length unit on the map represents 100 length units in real life", but a line
> segment in digital data has no fixed
> length: it can be drawn to any arbitrary scale by the display software.
>
> I assume there is a convention about what a scale ratio means in digital mapping.
> Please can someone enlighten me? Then
> I might be able to understand the first part of that statement (about the accuracy).
You are right scale doesn't mean as much in the digital world but...
there is still a strong correlation betwen map scale and appropriate
use < in a navigation sense >
So say your monitor is approximately 1/3 of a meter wide then the appropriate
zoom for DCW data is when your have approximately 300 kilometers in view
on the screen. < 1,000,000 * 1/3 = ~300,000 meters >
i.e. this is the scale < zoom > that this data was made to be 'accurate' at
Obviously FGFS is using this data is extreme 'overzoom'
googling on overzoom should lots of related hits
HTH
Norman
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